2 * sgen-gc.c: Simple generational GC.
5 * Paolo Molaro (lupus@ximian.com)
6 * Rodrigo Kumpera (kumpera@gmail.com)
8 * Copyright 2005-2011 Novell, Inc (http://www.novell.com)
9 * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
11 * Thread start/stop adapted from Boehm's GC:
12 * Copyright (c) 1994 by Xerox Corporation. All rights reserved.
13 * Copyright (c) 1996 by Silicon Graphics. All rights reserved.
14 * Copyright (c) 1998 by Fergus Henderson. All rights reserved.
15 * Copyright (c) 2000-2004 by Hewlett-Packard Company. All rights reserved.
16 * Copyright 2001-2003 Ximian, Inc
17 * Copyright 2003-2010 Novell, Inc.
18 * Copyright 2011 Xamarin, Inc.
19 * Copyright (C) 2012 Xamarin Inc
21 * This library is free software; you can redistribute it and/or
22 * modify it under the terms of the GNU Library General Public
23 * License 2.0 as published by the Free Software Foundation;
25 * This library is distributed in the hope that it will be useful,
26 * but WITHOUT ANY WARRANTY; without even the implied warranty of
27 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
28 * Library General Public License for more details.
30 * You should have received a copy of the GNU Library General Public
31 * License 2.0 along with this library; if not, write to the Free
32 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
34 * Important: allocation provides always zeroed memory, having to do
35 * a memset after allocation is deadly for performance.
36 * Memory usage at startup is currently as follows:
38 * 64 KB internal space
40 * We should provide a small memory config with half the sizes
42 * We currently try to make as few mono assumptions as possible:
43 * 1) 2-word header with no GC pointers in it (first vtable, second to store the
45 * 2) gc descriptor is the second word in the vtable (first word in the class)
46 * 3) 8 byte alignment is the minimum and enough (not true for special structures (SIMD), FIXME)
47 * 4) there is a function to get an object's size and the number of
48 * elements in an array.
49 * 5) we know the special way bounds are allocated for complex arrays
50 * 6) we know about proxies and how to treat them when domains are unloaded
52 * Always try to keep stack usage to a minimum: no recursive behaviour
53 * and no large stack allocs.
55 * General description.
56 * Objects are initially allocated in a nursery using a fast bump-pointer technique.
57 * When the nursery is full we start a nursery collection: this is performed with a
59 * When the old generation is full we start a copying GC of the old generation as well:
60 * this will be changed to mark&sweep with copying when fragmentation becomes to severe
61 * in the future. Maybe we'll even do both during the same collection like IMMIX.
63 * The things that complicate this description are:
64 * *) pinned objects: we can't move them so we need to keep track of them
65 * *) no precise info of the thread stacks and registers: we need to be able to
66 * quickly find the objects that may be referenced conservatively and pin them
67 * (this makes the first issues more important)
68 * *) large objects are too expensive to be dealt with using copying GC: we handle them
69 * with mark/sweep during major collections
70 * *) some objects need to not move even if they are small (interned strings, Type handles):
71 * we use mark/sweep for them, too: they are not allocated in the nursery, but inside
72 * PinnedChunks regions
78 *) we could have a function pointer in MonoClass to implement
79 customized write barriers for value types
81 *) investigate the stuff needed to advance a thread to a GC-safe
82 point (single-stepping, read from unmapped memory etc) and implement it.
83 This would enable us to inline allocations and write barriers, for example,
84 or at least parts of them, like the write barrier checks.
85 We may need this also for handling precise info on stacks, even simple things
86 as having uninitialized data on the stack and having to wait for the prolog
87 to zero it. Not an issue for the last frame that we scan conservatively.
88 We could always not trust the value in the slots anyway.
90 *) modify the jit to save info about references in stack locations:
91 this can be done just for locals as a start, so that at least
92 part of the stack is handled precisely.
94 *) test/fix endianess issues
96 *) Implement a card table as the write barrier instead of remembered
97 sets? Card tables are not easy to implement with our current
98 memory layout. We have several different kinds of major heap
99 objects: Small objects in regular blocks, small objects in pinned
100 chunks and LOS objects. If we just have a pointer we have no way
101 to tell which kind of object it points into, therefore we cannot
102 know where its card table is. The least we have to do to make
103 this happen is to get rid of write barriers for indirect stores.
106 *) Get rid of write barriers for indirect stores. We can do this by
107 telling the GC to wbarrier-register an object once we do an ldloca
108 or ldelema on it, and to unregister it once it's not used anymore
109 (it can only travel downwards on the stack). The problem with
110 unregistering is that it needs to happen eventually no matter
111 what, even if exceptions are thrown, the thread aborts, etc.
112 Rodrigo suggested that we could do only the registering part and
113 let the collector find out (pessimistically) when it's safe to
114 unregister, namely when the stack pointer of the thread that
115 registered the object is higher than it was when the registering
116 happened. This might make for a good first implementation to get
117 some data on performance.
119 *) Some sort of blacklist support? Blacklists is a concept from the
120 Boehm GC: if during a conservative scan we find pointers to an
121 area which we might use as heap, we mark that area as unusable, so
122 pointer retention by random pinning pointers is reduced.
124 *) experiment with max small object size (very small right now - 2kb,
125 because it's tied to the max freelist size)
127 *) add an option to mmap the whole heap in one chunk: it makes for many
128 simplifications in the checks (put the nursery at the top and just use a single
129 check for inclusion/exclusion): the issue this has is that on 32 bit systems it's
130 not flexible (too much of the address space may be used by default or we can't
131 increase the heap as needed) and we'd need a race-free mechanism to return memory
132 back to the system (mprotect(PROT_NONE) will still keep the memory allocated if it
133 was written to, munmap is needed, but the following mmap may not find the same segment
136 *) memzero the major fragments after restarting the world and optionally a smaller
139 *) investigate having fragment zeroing threads
141 *) separate locks for finalization and other minor stuff to reduce
144 *) try a different copying order to improve memory locality
146 *) a thread abort after a store but before the write barrier will
147 prevent the write barrier from executing
149 *) specialized dynamically generated markers/copiers
151 *) Dynamically adjust TLAB size to the number of threads. If we have
152 too many threads that do allocation, we might need smaller TLABs,
153 and we might get better performance with larger TLABs if we only
154 have a handful of threads. We could sum up the space left in all
155 assigned TLABs and if that's more than some percentage of the
156 nursery size, reduce the TLAB size.
158 *) Explore placing unreachable objects on unused nursery memory.
159 Instead of memset'ng a region to zero, place an int[] covering it.
160 A good place to start is add_nursery_frag. The tricky thing here is
161 placing those objects atomically outside of a collection.
163 *) Allocation should use asymmetric Dekker synchronization:
164 http://blogs.oracle.com/dave/resource/Asymmetric-Dekker-Synchronization.txt
165 This should help weak consistency archs.
172 #define _XOPEN_SOURCE
173 #define _DARWIN_C_SOURCE
179 #ifdef HAVE_PTHREAD_H
182 #ifdef HAVE_PTHREAD_NP_H
183 #include <pthread_np.h>
191 #include "mono/sgen/sgen-gc.h"
192 #include "mono/sgen/sgen-cardtable.h"
193 #include "mono/sgen/sgen-protocol.h"
194 #include "mono/sgen/sgen-memory-governor.h"
195 #include "mono/sgen/sgen-hash-table.h"
196 #include "mono/sgen/sgen-cardtable.h"
197 #include "mono/sgen/sgen-pinning.h"
198 #include "mono/sgen/sgen-workers.h"
199 #include "mono/sgen/sgen-client.h"
200 #include "mono/sgen/sgen-pointer-queue.h"
201 #include "mono/sgen/gc-internal-agnostic.h"
202 #include "mono/utils/mono-proclib.h"
203 #include "mono/utils/mono-memory-model.h"
204 #include "mono/utils/hazard-pointer.h"
206 #include <mono/utils/memcheck.h>
208 #undef pthread_create
210 #undef pthread_detach
213 * ######################################################################
214 * ######## Types and constants used by the GC.
215 * ######################################################################
218 /* 0 means not initialized, 1 is initialized, -1 means in progress */
219 static int gc_initialized = 0;
220 /* If set, check if we need to do something every X allocations */
221 gboolean has_per_allocation_action;
222 /* If set, do a heap check every X allocation */
223 guint32 verify_before_allocs = 0;
224 /* If set, do a minor collection before every X allocation */
225 guint32 collect_before_allocs = 0;
226 /* If set, do a whole heap check before each collection */
227 static gboolean whole_heap_check_before_collection = FALSE;
228 /* If set, do a heap consistency check before each minor collection */
229 static gboolean consistency_check_at_minor_collection = FALSE;
230 /* If set, do a mod union consistency check before each finishing collection pause */
231 static gboolean mod_union_consistency_check = FALSE;
232 /* If set, check whether mark bits are consistent after major collections */
233 static gboolean check_mark_bits_after_major_collection = FALSE;
234 /* If set, check that all nursery objects are pinned/not pinned, depending on context */
235 static gboolean check_nursery_objects_pinned = FALSE;
236 /* If set, do a few checks when the concurrent collector is used */
237 static gboolean do_concurrent_checks = FALSE;
238 /* If set, do a plausibility check on the scan_starts before and after
240 static gboolean do_scan_starts_check = FALSE;
243 * If the major collector is concurrent and this is FALSE, we will
244 * never initiate a synchronous major collection, unless requested via
247 static gboolean allow_synchronous_major = TRUE;
248 static gboolean disable_minor_collections = FALSE;
249 static gboolean disable_major_collections = FALSE;
250 static gboolean do_verify_nursery = FALSE;
251 static gboolean do_dump_nursery_content = FALSE;
252 static gboolean enable_nursery_canaries = FALSE;
254 #ifdef HEAVY_STATISTICS
255 guint64 stat_objects_alloced_degraded = 0;
256 guint64 stat_bytes_alloced_degraded = 0;
258 guint64 stat_copy_object_called_nursery = 0;
259 guint64 stat_objects_copied_nursery = 0;
260 guint64 stat_copy_object_called_major = 0;
261 guint64 stat_objects_copied_major = 0;
263 guint64 stat_scan_object_called_nursery = 0;
264 guint64 stat_scan_object_called_major = 0;
266 guint64 stat_slots_allocated_in_vain;
268 guint64 stat_nursery_copy_object_failed_from_space = 0;
269 guint64 stat_nursery_copy_object_failed_forwarded = 0;
270 guint64 stat_nursery_copy_object_failed_pinned = 0;
271 guint64 stat_nursery_copy_object_failed_to_space = 0;
273 static guint64 stat_wbarrier_add_to_global_remset = 0;
274 static guint64 stat_wbarrier_arrayref_copy = 0;
275 static guint64 stat_wbarrier_generic_store = 0;
276 static guint64 stat_wbarrier_generic_store_atomic = 0;
277 static guint64 stat_wbarrier_set_root = 0;
280 static guint64 stat_pinned_objects = 0;
282 static guint64 time_minor_pre_collection_fragment_clear = 0;
283 static guint64 time_minor_pinning = 0;
284 static guint64 time_minor_scan_remsets = 0;
285 static guint64 time_minor_scan_pinned = 0;
286 static guint64 time_minor_scan_roots = 0;
287 static guint64 time_minor_finish_gray_stack = 0;
288 static guint64 time_minor_fragment_creation = 0;
290 static guint64 time_major_pre_collection_fragment_clear = 0;
291 static guint64 time_major_pinning = 0;
292 static guint64 time_major_scan_pinned = 0;
293 static guint64 time_major_scan_roots = 0;
294 static guint64 time_major_scan_mod_union = 0;
295 static guint64 time_major_finish_gray_stack = 0;
296 static guint64 time_major_free_bigobjs = 0;
297 static guint64 time_major_los_sweep = 0;
298 static guint64 time_major_sweep = 0;
299 static guint64 time_major_fragment_creation = 0;
301 static guint64 time_max = 0;
303 static SGEN_TV_DECLARE (time_major_conc_collection_start);
304 static SGEN_TV_DECLARE (time_major_conc_collection_end);
306 static SGEN_TV_DECLARE (last_minor_collection_start_tv);
307 static SGEN_TV_DECLARE (last_minor_collection_end_tv);
309 int gc_debug_level = 0;
314 mono_gc_flush_info (void)
316 fflush (gc_debug_file);
320 #define TV_DECLARE SGEN_TV_DECLARE
321 #define TV_GETTIME SGEN_TV_GETTIME
322 #define TV_ELAPSED SGEN_TV_ELAPSED
324 static SGEN_TV_DECLARE (sgen_init_timestamp);
326 NurseryClearPolicy nursery_clear_policy = CLEAR_AT_TLAB_CREATION;
328 #define object_is_forwarded SGEN_OBJECT_IS_FORWARDED
329 #define object_is_pinned SGEN_OBJECT_IS_PINNED
330 #define pin_object SGEN_PIN_OBJECT
332 #define ptr_in_nursery sgen_ptr_in_nursery
334 #define LOAD_VTABLE SGEN_LOAD_VTABLE
337 nursery_canaries_enabled (void)
339 return enable_nursery_canaries;
342 #define safe_object_get_size sgen_safe_object_get_size
345 * ######################################################################
346 * ######## Global data.
347 * ######################################################################
349 LOCK_DECLARE (gc_mutex);
350 gboolean sgen_try_free_some_memory;
352 #define SCAN_START_SIZE SGEN_SCAN_START_SIZE
354 size_t degraded_mode = 0;
356 static mword bytes_pinned_from_failed_allocation = 0;
358 GCMemSection *nursery_section = NULL;
359 static volatile mword lowest_heap_address = ~(mword)0;
360 static volatile mword highest_heap_address = 0;
362 LOCK_DECLARE (sgen_interruption_mutex);
364 int current_collection_generation = -1;
365 static volatile gboolean concurrent_collection_in_progress = FALSE;
367 /* objects that are ready to be finalized */
368 static SgenPointerQueue fin_ready_queue = SGEN_POINTER_QUEUE_INIT (INTERNAL_MEM_FINALIZE_READY);
369 static SgenPointerQueue critical_fin_queue = SGEN_POINTER_QUEUE_INIT (INTERNAL_MEM_FINALIZE_READY);
371 /* registered roots: the key to the hash is the root start address */
373 * Different kinds of roots are kept separate to speed up pin_from_roots () for example.
375 SgenHashTable roots_hash [ROOT_TYPE_NUM] = {
376 SGEN_HASH_TABLE_INIT (INTERNAL_MEM_ROOTS_TABLE, INTERNAL_MEM_ROOT_RECORD, sizeof (RootRecord), sgen_aligned_addr_hash, NULL),
377 SGEN_HASH_TABLE_INIT (INTERNAL_MEM_ROOTS_TABLE, INTERNAL_MEM_ROOT_RECORD, sizeof (RootRecord), sgen_aligned_addr_hash, NULL),
378 SGEN_HASH_TABLE_INIT (INTERNAL_MEM_ROOTS_TABLE, INTERNAL_MEM_ROOT_RECORD, sizeof (RootRecord), sgen_aligned_addr_hash, NULL)
380 static mword roots_size = 0; /* amount of memory in the root set */
382 /* The size of a TLAB */
383 /* The bigger the value, the less often we have to go to the slow path to allocate a new
384 * one, but the more space is wasted by threads not allocating much memory.
386 * FIXME: Make this self-tuning for each thread.
388 guint32 tlab_size = (1024 * 4);
390 #define MAX_SMALL_OBJ_SIZE SGEN_MAX_SMALL_OBJ_SIZE
392 #define ALLOC_ALIGN SGEN_ALLOC_ALIGN
394 #define ALIGN_UP SGEN_ALIGN_UP
396 #ifdef SGEN_DEBUG_INTERNAL_ALLOC
397 MonoNativeThreadId main_gc_thread = NULL;
400 /*Object was pinned during the current collection*/
401 static mword objects_pinned;
404 * ######################################################################
405 * ######## Macros and function declarations.
406 * ######################################################################
409 typedef SgenGrayQueue GrayQueue;
411 /* forward declarations */
412 static void scan_from_registered_roots (char *addr_start, char *addr_end, int root_type, ScanCopyContext ctx);
414 static void pin_from_roots (void *start_nursery, void *end_nursery, ScanCopyContext ctx);
415 static void finish_gray_stack (int generation, ScanCopyContext ctx);
418 SgenMajorCollector major_collector;
419 SgenMinorCollector sgen_minor_collector;
420 /* FIXME: get rid of this */
421 static GrayQueue gray_queue;
423 static SgenRememberedSet remset;
425 /* The gray queue to use from the main collection thread. */
426 #define WORKERS_DISTRIBUTE_GRAY_QUEUE (&gray_queue)
429 * The gray queue a worker job must use. If we're not parallel or
430 * concurrent, we use the main gray queue.
432 static SgenGrayQueue*
433 sgen_workers_get_job_gray_queue (WorkerData *worker_data)
435 return worker_data ? &worker_data->private_gray_queue : WORKERS_DISTRIBUTE_GRAY_QUEUE;
439 gray_queue_redirect (SgenGrayQueue *queue)
441 gboolean wake = FALSE;
444 GrayQueueSection *section = sgen_gray_object_dequeue_section (queue);
447 sgen_section_gray_queue_enqueue (queue->alloc_prepare_data, section);
452 g_assert (concurrent_collection_in_progress);
453 sgen_workers_ensure_awake ();
458 gray_queue_enable_redirect (SgenGrayQueue *queue)
460 if (!concurrent_collection_in_progress)
463 sgen_gray_queue_set_alloc_prepare (queue, gray_queue_redirect, sgen_workers_get_distribute_section_gray_queue ());
464 gray_queue_redirect (queue);
468 sgen_scan_area_with_callback (char *start, char *end, IterateObjectCallbackFunc callback, void *data, gboolean allow_flags)
470 while (start < end) {
474 if (!*(void**)start) {
475 start += sizeof (void*); /* should be ALLOC_ALIGN, really */
480 if (!(obj = SGEN_OBJECT_IS_FORWARDED (start)))
486 if (!sgen_client_object_is_array_fill ((GCObject*)obj)) {
487 CHECK_CANARY_FOR_OBJECT ((GCObject*)obj);
488 size = ALIGN_UP (safe_object_get_size ((GCObject*)obj));
489 callback ((GCObject*)obj, size, data);
490 CANARIFY_SIZE (size);
492 size = ALIGN_UP (safe_object_get_size ((GCObject*)obj));
500 * sgen_add_to_global_remset:
502 * The global remset contains locations which point into newspace after
503 * a minor collection. This can happen if the objects they point to are pinned.
505 * LOCKING: If called from a parallel collector, the global remset
506 * lock must be held. For serial collectors that is not necessary.
509 sgen_add_to_global_remset (gpointer ptr, gpointer obj)
511 SGEN_ASSERT (5, sgen_ptr_in_nursery (obj), "Target pointer of global remset must be in the nursery");
513 HEAVY_STAT (++stat_wbarrier_add_to_global_remset);
515 if (!major_collector.is_concurrent) {
516 SGEN_ASSERT (5, current_collection_generation != -1, "Global remsets can only be added during collections");
518 if (current_collection_generation == -1)
519 SGEN_ASSERT (5, sgen_concurrent_collection_in_progress (), "Global remsets outside of collection pauses can only be added by the concurrent collector");
522 if (!object_is_pinned (obj))
523 SGEN_ASSERT (5, sgen_minor_collector.is_split || sgen_concurrent_collection_in_progress (), "Non-pinned objects can only remain in nursery if it is a split nursery");
524 else if (sgen_cement_lookup_or_register (obj))
527 remset.record_pointer (ptr);
529 sgen_pin_stats_register_global_remset (obj);
531 SGEN_LOG (8, "Adding global remset for %p", ptr);
532 binary_protocol_global_remset (ptr, obj, (gpointer)SGEN_LOAD_VTABLE (obj));
536 * sgen_drain_gray_stack:
538 * Scan objects in the gray stack until the stack is empty. This should be called
539 * frequently after each object is copied, to achieve better locality and cache
542 * max_objs is the maximum number of objects to scan, or -1 to scan until the stack is
546 sgen_drain_gray_stack (int max_objs, ScanCopyContext ctx)
548 ScanObjectFunc scan_func = ctx.ops->scan_object;
549 GrayQueue *queue = ctx.queue;
551 if (current_collection_generation == GENERATION_OLD && major_collector.drain_gray_stack)
552 return major_collector.drain_gray_stack (ctx);
556 for (i = 0; i != max_objs; ++i) {
559 GRAY_OBJECT_DEQUEUE (queue, &obj, &desc);
562 SGEN_LOG (9, "Precise gray object scan %p (%s)", obj, sgen_client_vtable_get_name (SGEN_LOAD_VTABLE (obj)));
563 scan_func (obj, desc, queue);
565 } while (max_objs < 0);
570 * Addresses in the pin queue are already sorted. This function finds
571 * the object header for each address and pins the object. The
572 * addresses must be inside the nursery section. The (start of the)
573 * address array is overwritten with the addresses of the actually
574 * pinned objects. Return the number of pinned objects.
577 pin_objects_from_nursery_pin_queue (gboolean do_scan_objects, ScanCopyContext ctx)
579 GCMemSection *section = nursery_section;
580 void **start = sgen_pinning_get_entry (section->pin_queue_first_entry);
581 void **end = sgen_pinning_get_entry (section->pin_queue_last_entry);
582 void *start_nursery = section->data;
583 void *end_nursery = section->next_data;
588 void *pinning_front = start_nursery;
590 void **definitely_pinned = start;
591 ScanObjectFunc scan_func = ctx.ops->scan_object;
592 SgenGrayQueue *queue = ctx.queue;
594 sgen_nursery_allocator_prepare_for_pinning ();
596 while (start < end) {
597 GCObject *obj_to_pin = NULL;
598 size_t obj_to_pin_size = 0;
603 SGEN_ASSERT (0, addr >= start_nursery && addr < end_nursery, "Potential pinning address out of range");
604 SGEN_ASSERT (0, addr >= last, "Pin queue not sorted");
611 SGEN_LOG (5, "Considering pinning addr %p", addr);
612 /* We've already processed everything up to pinning_front. */
613 if (addr < pinning_front) {
619 * Find the closest scan start <= addr. We might search backward in the
620 * scan_starts array because entries might be NULL. In the worst case we
621 * start at start_nursery.
623 idx = ((char*)addr - (char*)section->data) / SCAN_START_SIZE;
624 SGEN_ASSERT (0, idx < section->num_scan_start, "Scan start index out of range");
625 search_start = (void*)section->scan_starts [idx];
626 if (!search_start || search_start > addr) {
629 search_start = section->scan_starts [idx];
630 if (search_start && search_start <= addr)
633 if (!search_start || search_start > addr)
634 search_start = start_nursery;
638 * If the pinning front is closer than the scan start we found, start
639 * searching at the front.
641 if (search_start < pinning_front)
642 search_start = pinning_front;
645 * Now addr should be in an object a short distance from search_start.
647 * search_start must point to zeroed mem or point to an object.
650 size_t obj_size, canarified_obj_size;
653 if (!*(void**)search_start) {
654 search_start = (void*)ALIGN_UP ((mword)search_start + sizeof (gpointer));
655 /* The loop condition makes sure we don't overrun addr. */
659 canarified_obj_size = obj_size = ALIGN_UP (safe_object_get_size ((GCObject*)search_start));
662 * Filler arrays are marked by an invalid sync word. We don't
663 * consider them for pinning. They are not delimited by canaries,
666 if (!sgen_client_object_is_array_fill ((GCObject*)search_start)) {
667 CHECK_CANARY_FOR_OBJECT (search_start);
668 CANARIFY_SIZE (canarified_obj_size);
670 if (addr >= search_start && (char*)addr < (char*)search_start + obj_size) {
671 /* This is the object we're looking for. */
672 obj_to_pin = (GCObject*)search_start;
673 obj_to_pin_size = canarified_obj_size;
678 /* Skip to the next object */
679 search_start = (void*)((char*)search_start + canarified_obj_size);
680 } while (search_start <= addr);
682 /* We've searched past the address we were looking for. */
684 pinning_front = search_start;
685 goto next_pin_queue_entry;
689 * We've found an object to pin. It might still be a dummy array, but we
690 * can advance the pinning front in any case.
692 pinning_front = (char*)obj_to_pin + obj_to_pin_size;
695 * If this is a dummy array marking the beginning of a nursery
696 * fragment, we don't pin it.
698 if (sgen_client_object_is_array_fill (obj_to_pin))
699 goto next_pin_queue_entry;
702 * Finally - pin the object!
704 desc = sgen_obj_get_descriptor_safe (obj_to_pin);
705 if (do_scan_objects) {
706 scan_func (obj_to_pin, desc, queue);
708 SGEN_LOG (4, "Pinned object %p, vtable %p (%s), count %d\n",
709 obj_to_pin, *(void**)obj_to_pin, sgen_client_vtable_get_name (SGEN_LOAD_VTABLE (obj_to_pin)), count);
710 binary_protocol_pin (obj_to_pin,
711 (gpointer)LOAD_VTABLE (obj_to_pin),
712 safe_object_get_size (obj_to_pin));
714 pin_object (obj_to_pin);
715 GRAY_OBJECT_ENQUEUE (queue, obj_to_pin, desc);
716 sgen_pin_stats_register_object (obj_to_pin, obj_to_pin_size);
717 definitely_pinned [count] = obj_to_pin;
721 next_pin_queue_entry:
725 sgen_client_nursery_objects_pinned (definitely_pinned, count);
726 stat_pinned_objects += count;
731 pin_objects_in_nursery (gboolean do_scan_objects, ScanCopyContext ctx)
735 if (nursery_section->pin_queue_first_entry == nursery_section->pin_queue_last_entry)
738 reduced_to = pin_objects_from_nursery_pin_queue (do_scan_objects, ctx);
739 nursery_section->pin_queue_last_entry = nursery_section->pin_queue_first_entry + reduced_to;
743 * This function is only ever called (via `collector_pin_object()` in `sgen-copy-object.h`)
744 * when we can't promote an object because we're out of memory.
747 sgen_pin_object (GCObject *object, GrayQueue *queue)
750 * All pinned objects are assumed to have been staged, so we need to stage as well.
751 * Also, the count of staged objects shows that "late pinning" happened.
753 sgen_pin_stage_ptr (object);
755 SGEN_PIN_OBJECT (object);
756 binary_protocol_pin (object, (gpointer)LOAD_VTABLE (object), safe_object_get_size (object));
759 sgen_pin_stats_register_object (object, safe_object_get_size (object));
761 GRAY_OBJECT_ENQUEUE (queue, object, sgen_obj_get_descriptor_safe (object));
764 /* Sort the addresses in array in increasing order.
765 * Done using a by-the book heap sort. Which has decent and stable performance, is pretty cache efficient.
768 sgen_sort_addresses (void **array, size_t size)
773 for (i = 1; i < size; ++i) {
776 size_t parent = (child - 1) / 2;
778 if (array [parent] >= array [child])
781 tmp = array [parent];
782 array [parent] = array [child];
789 for (i = size - 1; i > 0; --i) {
792 array [i] = array [0];
798 while (root * 2 + 1 <= end) {
799 size_t child = root * 2 + 1;
801 if (child < end && array [child] < array [child + 1])
803 if (array [root] >= array [child])
807 array [root] = array [child];
816 * Scan the memory between start and end and queue values which could be pointers
817 * to the area between start_nursery and end_nursery for later consideration.
818 * Typically used for thread stacks.
821 sgen_conservatively_pin_objects_from (void **start, void **end, void *start_nursery, void *end_nursery, int pin_type)
825 #ifdef VALGRIND_MAKE_MEM_DEFINED_IF_ADDRESSABLE
826 VALGRIND_MAKE_MEM_DEFINED_IF_ADDRESSABLE (start, (char*)end - (char*)start);
829 while (start < end) {
831 * *start can point to the middle of an object
832 * note: should we handle pointing at the end of an object?
833 * pinning in C# code disallows pointing at the end of an object
834 * but there is some small chance that an optimizing C compiler
835 * may keep the only reference to an object by pointing
836 * at the end of it. We ignore this small chance for now.
837 * Pointers to the end of an object are indistinguishable
838 * from pointers to the start of the next object in memory
839 * so if we allow that we'd need to pin two objects...
840 * We queue the pointer in an array, the
841 * array will then be sorted and uniqued. This way
842 * we can coalesce several pinning pointers and it should
843 * be faster since we'd do a memory scan with increasing
844 * addresses. Note: we can align the address to the allocation
845 * alignment, so the unique process is more effective.
847 mword addr = (mword)*start;
848 addr &= ~(ALLOC_ALIGN - 1);
849 if (addr >= (mword)start_nursery && addr < (mword)end_nursery) {
850 SGEN_LOG (6, "Pinning address %p from %p", (void*)addr, start);
851 sgen_pin_stage_ptr ((void*)addr);
852 binary_protocol_pin_stage (start, (void*)addr);
853 sgen_pin_stats_register_address ((char*)addr, pin_type);
859 SGEN_LOG (7, "found %d potential pinned heap pointers", count);
863 * The first thing we do in a collection is to identify pinned objects.
864 * This function considers all the areas of memory that need to be
865 * conservatively scanned.
868 pin_from_roots (void *start_nursery, void *end_nursery, ScanCopyContext ctx)
872 SGEN_LOG (2, "Scanning pinned roots (%d bytes, %d/%d entries)", (int)roots_size, roots_hash [ROOT_TYPE_NORMAL].num_entries, roots_hash [ROOT_TYPE_PINNED].num_entries);
873 /* objects pinned from the API are inside these roots */
874 SGEN_HASH_TABLE_FOREACH (&roots_hash [ROOT_TYPE_PINNED], start_root, root) {
875 SGEN_LOG (6, "Pinned roots %p-%p", start_root, root->end_root);
876 sgen_conservatively_pin_objects_from (start_root, (void**)root->end_root, start_nursery, end_nursery, PIN_TYPE_OTHER);
877 } SGEN_HASH_TABLE_FOREACH_END;
878 /* now deal with the thread stacks
879 * in the future we should be able to conservatively scan only:
880 * *) the cpu registers
881 * *) the unmanaged stack frames
882 * *) the _last_ managed stack frame
883 * *) pointers slots in managed frames
885 sgen_client_scan_thread_data (start_nursery, end_nursery, FALSE, ctx);
889 unpin_objects_from_queue (SgenGrayQueue *queue)
894 GRAY_OBJECT_DEQUEUE (queue, &addr, &desc);
897 g_assert (SGEN_OBJECT_IS_PINNED (addr));
898 SGEN_UNPIN_OBJECT (addr);
903 single_arg_user_copy_or_mark (GCObject **obj, void *gc_data)
905 ScanCopyContext *ctx = gc_data;
906 ctx->ops->copy_or_mark_object (obj, ctx->queue);
910 * The memory area from start_root to end_root contains pointers to objects.
911 * Their position is precisely described by @desc (this means that the pointer
912 * can be either NULL or the pointer to the start of an object).
913 * This functions copies them to to_space updates them.
915 * This function is not thread-safe!
918 precisely_scan_objects_from (void** start_root, void** end_root, char* n_start, char *n_end, SgenDescriptor desc, ScanCopyContext ctx)
920 CopyOrMarkObjectFunc copy_func = ctx.ops->copy_or_mark_object;
921 SgenGrayQueue *queue = ctx.queue;
923 switch (desc & ROOT_DESC_TYPE_MASK) {
924 case ROOT_DESC_BITMAP:
925 desc >>= ROOT_DESC_TYPE_SHIFT;
927 if ((desc & 1) && *start_root) {
928 copy_func ((GCObject**)start_root, queue);
929 SGEN_LOG (9, "Overwrote root at %p with %p", start_root, *start_root);
935 case ROOT_DESC_COMPLEX: {
936 gsize *bitmap_data = sgen_get_complex_descriptor_bitmap (desc);
937 gsize bwords = (*bitmap_data) - 1;
938 void **start_run = start_root;
940 while (bwords-- > 0) {
941 gsize bmap = *bitmap_data++;
942 void **objptr = start_run;
944 if ((bmap & 1) && *objptr) {
945 copy_func ((GCObject**)objptr, queue);
946 SGEN_LOG (9, "Overwrote root at %p with %p", objptr, *objptr);
951 start_run += GC_BITS_PER_WORD;
955 case ROOT_DESC_USER: {
956 SgenUserRootMarkFunc marker = sgen_get_user_descriptor_func (desc);
957 marker (start_root, single_arg_user_copy_or_mark, &ctx);
960 case ROOT_DESC_RUN_LEN:
961 g_assert_not_reached ();
963 g_assert_not_reached ();
968 reset_heap_boundaries (void)
970 lowest_heap_address = ~(mword)0;
971 highest_heap_address = 0;
975 sgen_update_heap_boundaries (mword low, mword high)
980 old = lowest_heap_address;
983 } while (SGEN_CAS_PTR ((gpointer*)&lowest_heap_address, (gpointer)low, (gpointer)old) != (gpointer)old);
986 old = highest_heap_address;
989 } while (SGEN_CAS_PTR ((gpointer*)&highest_heap_address, (gpointer)high, (gpointer)old) != (gpointer)old);
993 * Allocate and setup the data structures needed to be able to allocate objects
994 * in the nursery. The nursery is stored in nursery_section.
999 GCMemSection *section;
1004 if (nursery_section)
1006 SGEN_LOG (2, "Allocating nursery size: %zu", (size_t)sgen_nursery_size);
1007 /* later we will alloc a larger area for the nursery but only activate
1008 * what we need. The rest will be used as expansion if we have too many pinned
1009 * objects in the existing nursery.
1011 /* FIXME: handle OOM */
1012 section = sgen_alloc_internal (INTERNAL_MEM_SECTION);
1014 alloc_size = sgen_nursery_size;
1016 /* If there isn't enough space even for the nursery we should simply abort. */
1017 g_assert (sgen_memgov_try_alloc_space (alloc_size, SPACE_NURSERY));
1019 data = major_collector.alloc_heap (alloc_size, alloc_size, DEFAULT_NURSERY_BITS);
1020 sgen_update_heap_boundaries ((mword)data, (mword)(data + sgen_nursery_size));
1021 SGEN_LOG (4, "Expanding nursery size (%p-%p): %lu, total: %lu", data, data + alloc_size, (unsigned long)sgen_nursery_size, (unsigned long)sgen_gc_get_total_heap_allocation ());
1022 section->data = section->next_data = data;
1023 section->size = alloc_size;
1024 section->end_data = data + sgen_nursery_size;
1025 scan_starts = (alloc_size + SCAN_START_SIZE - 1) / SCAN_START_SIZE;
1026 section->scan_starts = sgen_alloc_internal_dynamic (sizeof (char*) * scan_starts, INTERNAL_MEM_SCAN_STARTS, TRUE);
1027 section->num_scan_start = scan_starts;
1029 nursery_section = section;
1031 sgen_nursery_allocator_set_nursery_bounds (data, data + sgen_nursery_size);
1035 mono_gc_get_logfile (void)
1037 return gc_debug_file;
1041 scan_finalizer_entries (SgenPointerQueue *fin_queue, ScanCopyContext ctx)
1043 CopyOrMarkObjectFunc copy_func = ctx.ops->copy_or_mark_object;
1044 SgenGrayQueue *queue = ctx.queue;
1047 for (i = 0; i < fin_queue->next_slot; ++i) {
1048 GCObject *obj = fin_queue->data [i];
1051 SGEN_LOG (5, "Scan of fin ready object: %p (%s)\n", obj, sgen_client_vtable_get_name (SGEN_LOAD_VTABLE (obj)));
1052 copy_func ((GCObject**)&fin_queue->data [i], queue);
1057 generation_name (int generation)
1059 switch (generation) {
1060 case GENERATION_NURSERY: return "nursery";
1061 case GENERATION_OLD: return "old";
1062 default: g_assert_not_reached ();
1067 sgen_generation_name (int generation)
1069 return generation_name (generation);
1073 finish_gray_stack (int generation, ScanCopyContext ctx)
1077 int done_with_ephemerons, ephemeron_rounds = 0;
1078 char *start_addr = generation == GENERATION_NURSERY ? sgen_get_nursery_start () : NULL;
1079 char *end_addr = generation == GENERATION_NURSERY ? sgen_get_nursery_end () : (char*)-1;
1080 SgenGrayQueue *queue = ctx.queue;
1083 * We copied all the reachable objects. Now it's the time to copy
1084 * the objects that were not referenced by the roots, but by the copied objects.
1085 * we built a stack of objects pointed to by gray_start: they are
1086 * additional roots and we may add more items as we go.
1087 * We loop until gray_start == gray_objects which means no more objects have
1088 * been added. Note this is iterative: no recursion is involved.
1089 * We need to walk the LO list as well in search of marked big objects
1090 * (use a flag since this is needed only on major collections). We need to loop
1091 * here as well, so keep a counter of marked LO (increasing it in copy_object).
1092 * To achieve better cache locality and cache usage, we drain the gray stack
1093 * frequently, after each object is copied, and just finish the work here.
1095 sgen_drain_gray_stack (-1, ctx);
1097 SGEN_LOG (2, "%s generation done", generation_name (generation));
1100 Reset bridge data, we might have lingering data from a previous collection if this is a major
1101 collection trigged by minor overflow.
1103 We must reset the gathered bridges since their original block might be evacuated due to major
1104 fragmentation in the meanwhile and the bridge code should not have to deal with that.
1106 if (sgen_client_bridge_need_processing ())
1107 sgen_client_bridge_reset_data ();
1110 * Walk the ephemeron tables marking all values with reachable keys. This must be completely done
1111 * before processing finalizable objects and non-tracking weak links to avoid finalizing/clearing
1112 * objects that are in fact reachable.
1114 done_with_ephemerons = 0;
1116 done_with_ephemerons = sgen_client_mark_ephemerons (ctx);
1117 sgen_drain_gray_stack (-1, ctx);
1119 } while (!done_with_ephemerons);
1121 sgen_client_mark_togglerefs (start_addr, end_addr, ctx);
1123 if (sgen_client_bridge_need_processing ()) {
1124 /*Make sure the gray stack is empty before we process bridge objects so we get liveness right*/
1125 sgen_drain_gray_stack (-1, ctx);
1126 sgen_collect_bridge_objects (generation, ctx);
1127 if (generation == GENERATION_OLD)
1128 sgen_collect_bridge_objects (GENERATION_NURSERY, ctx);
1131 Do the first bridge step here, as the collector liveness state will become useless after that.
1133 An important optimization is to only proccess the possibly dead part of the object graph and skip
1134 over all live objects as we transitively know everything they point must be alive too.
1136 The above invariant is completely wrong if we let the gray queue be drained and mark/copy everything.
1138 This has the unfortunate side effect of making overflow collections perform the first step twice, but
1139 given we now have heuristics that perform major GC in anticipation of minor overflows this should not
1142 sgen_client_bridge_processing_stw_step ();
1146 Make sure we drain the gray stack before processing disappearing links and finalizers.
1147 If we don't make sure it is empty we might wrongly see a live object as dead.
1149 sgen_drain_gray_stack (-1, ctx);
1152 We must clear weak links that don't track resurrection before processing object ready for
1153 finalization so they can be cleared before that.
1155 sgen_null_link_in_range (generation, TRUE, ctx);
1156 if (generation == GENERATION_OLD)
1157 sgen_null_link_in_range (GENERATION_NURSERY, TRUE, ctx);
1160 /* walk the finalization queue and move also the objects that need to be
1161 * finalized: use the finalized objects as new roots so the objects they depend
1162 * on are also not reclaimed. As with the roots above, only objects in the nursery
1163 * are marked/copied.
1165 sgen_finalize_in_range (generation, ctx);
1166 if (generation == GENERATION_OLD)
1167 sgen_finalize_in_range (GENERATION_NURSERY, ctx);
1168 /* drain the new stack that might have been created */
1169 SGEN_LOG (6, "Precise scan of gray area post fin");
1170 sgen_drain_gray_stack (-1, ctx);
1173 * This must be done again after processing finalizable objects since CWL slots are cleared only after the key is finalized.
1175 done_with_ephemerons = 0;
1177 done_with_ephemerons = sgen_client_mark_ephemerons (ctx);
1178 sgen_drain_gray_stack (-1, ctx);
1180 } while (!done_with_ephemerons);
1182 sgen_client_clear_unreachable_ephemerons (ctx);
1185 * We clear togglerefs only after all possible chances of revival are done.
1186 * This is semantically more inline with what users expect and it allows for
1187 * user finalizers to correctly interact with TR objects.
1189 sgen_client_clear_togglerefs (start_addr, end_addr, ctx);
1192 SGEN_LOG (2, "Finalize queue handling scan for %s generation: %ld usecs %d ephemeron rounds", generation_name (generation), TV_ELAPSED (atv, btv), ephemeron_rounds);
1195 * handle disappearing links
1196 * Note we do this after checking the finalization queue because if an object
1197 * survives (at least long enough to be finalized) we don't clear the link.
1198 * This also deals with a possible issue with the monitor reclamation: with the Boehm
1199 * GC a finalized object my lose the monitor because it is cleared before the finalizer is
1202 g_assert (sgen_gray_object_queue_is_empty (queue));
1204 sgen_null_link_in_range (generation, FALSE, ctx);
1205 if (generation == GENERATION_OLD)
1206 sgen_null_link_in_range (GENERATION_NURSERY, FALSE, ctx);
1207 if (sgen_gray_object_queue_is_empty (queue))
1209 sgen_drain_gray_stack (-1, ctx);
1212 g_assert (sgen_gray_object_queue_is_empty (queue));
1214 sgen_gray_object_queue_trim_free_list (queue);
1218 sgen_check_section_scan_starts (GCMemSection *section)
1221 for (i = 0; i < section->num_scan_start; ++i) {
1222 if (section->scan_starts [i]) {
1223 mword size = safe_object_get_size ((GCObject*) section->scan_starts [i]);
1224 SGEN_ASSERT (0, size >= SGEN_CLIENT_MINIMUM_OBJECT_SIZE && size <= MAX_SMALL_OBJ_SIZE, "Weird object size at scan starts.");
1230 check_scan_starts (void)
1232 if (!do_scan_starts_check)
1234 sgen_check_section_scan_starts (nursery_section);
1235 major_collector.check_scan_starts ();
1239 scan_from_registered_roots (char *addr_start, char *addr_end, int root_type, ScanCopyContext ctx)
1243 SGEN_HASH_TABLE_FOREACH (&roots_hash [root_type], start_root, root) {
1244 SGEN_LOG (6, "Precise root scan %p-%p (desc: %p)", start_root, root->end_root, (void*)root->root_desc);
1245 precisely_scan_objects_from (start_root, (void**)root->end_root, addr_start, addr_end, root->root_desc, ctx);
1246 } SGEN_HASH_TABLE_FOREACH_END;
1252 static gboolean inited = FALSE;
1257 mono_counters_register ("Collection max time", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME | MONO_COUNTER_MONOTONIC, &time_max);
1259 mono_counters_register ("Minor fragment clear", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_pre_collection_fragment_clear);
1260 mono_counters_register ("Minor pinning", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_pinning);
1261 mono_counters_register ("Minor scan remembered set", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_scan_remsets);
1262 mono_counters_register ("Minor scan pinned", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_scan_pinned);
1263 mono_counters_register ("Minor scan roots", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_scan_roots);
1264 mono_counters_register ("Minor fragment creation", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_minor_fragment_creation);
1266 mono_counters_register ("Major fragment clear", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_major_pre_collection_fragment_clear);
1267 mono_counters_register ("Major pinning", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_major_pinning);
1268 mono_counters_register ("Major scan pinned", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_major_scan_pinned);
1269 mono_counters_register ("Major scan roots", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_major_scan_roots);
1270 mono_counters_register ("Major scan mod union", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_major_scan_mod_union);
1271 mono_counters_register ("Major finish gray stack", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_major_finish_gray_stack);
1272 mono_counters_register ("Major free big objects", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_major_free_bigobjs);
1273 mono_counters_register ("Major LOS sweep", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_major_los_sweep);
1274 mono_counters_register ("Major sweep", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_major_sweep);
1275 mono_counters_register ("Major fragment creation", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &time_major_fragment_creation);
1277 mono_counters_register ("Number of pinned objects", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_pinned_objects);
1279 #ifdef HEAVY_STATISTICS
1280 mono_counters_register ("WBarrier remember pointer", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_wbarrier_add_to_global_remset);
1281 mono_counters_register ("WBarrier arrayref copy", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_wbarrier_arrayref_copy);
1282 mono_counters_register ("WBarrier generic store called", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_wbarrier_generic_store);
1283 mono_counters_register ("WBarrier generic atomic store called", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_wbarrier_generic_store_atomic);
1284 mono_counters_register ("WBarrier set root", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_wbarrier_set_root);
1286 mono_counters_register ("# objects allocated degraded", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_objects_alloced_degraded);
1287 mono_counters_register ("bytes allocated degraded", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_bytes_alloced_degraded);
1289 mono_counters_register ("# copy_object() called (nursery)", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copy_object_called_nursery);
1290 mono_counters_register ("# objects copied (nursery)", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_objects_copied_nursery);
1291 mono_counters_register ("# copy_object() called (major)", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copy_object_called_major);
1292 mono_counters_register ("# objects copied (major)", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_objects_copied_major);
1294 mono_counters_register ("# scan_object() called (nursery)", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scan_object_called_nursery);
1295 mono_counters_register ("# scan_object() called (major)", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scan_object_called_major);
1297 mono_counters_register ("Slots allocated in vain", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_slots_allocated_in_vain);
1299 mono_counters_register ("# nursery copy_object() failed from space", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_nursery_copy_object_failed_from_space);
1300 mono_counters_register ("# nursery copy_object() failed forwarded", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_nursery_copy_object_failed_forwarded);
1301 mono_counters_register ("# nursery copy_object() failed pinned", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_nursery_copy_object_failed_pinned);
1302 mono_counters_register ("# nursery copy_object() failed to space", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_nursery_copy_object_failed_to_space);
1304 sgen_nursery_allocator_init_heavy_stats ();
1312 reset_pinned_from_failed_allocation (void)
1314 bytes_pinned_from_failed_allocation = 0;
1318 sgen_set_pinned_from_failed_allocation (mword objsize)
1320 bytes_pinned_from_failed_allocation += objsize;
1324 sgen_collection_is_concurrent (void)
1326 switch (current_collection_generation) {
1327 case GENERATION_NURSERY:
1329 case GENERATION_OLD:
1330 return concurrent_collection_in_progress;
1332 g_error ("Invalid current generation %d", current_collection_generation);
1338 sgen_concurrent_collection_in_progress (void)
1340 return concurrent_collection_in_progress;
1344 SgenThreadPoolJob job;
1345 SgenObjectOperations *ops;
1349 job_remembered_set_scan (void *worker_data_untyped, SgenThreadPoolJob *job)
1351 WorkerData *worker_data = worker_data_untyped;
1352 ScanJob *job_data = (ScanJob*)job;
1353 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (job_data->ops, sgen_workers_get_job_gray_queue (worker_data));
1354 remset.scan_remsets (ctx);
1358 SgenThreadPoolJob job;
1359 SgenObjectOperations *ops;
1363 } ScanFromRegisteredRootsJob;
1366 job_scan_from_registered_roots (void *worker_data_untyped, SgenThreadPoolJob *job)
1368 WorkerData *worker_data = worker_data_untyped;
1369 ScanFromRegisteredRootsJob *job_data = (ScanFromRegisteredRootsJob*)job;
1370 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (job_data->ops, sgen_workers_get_job_gray_queue (worker_data));
1372 scan_from_registered_roots (job_data->heap_start, job_data->heap_end, job_data->root_type, ctx);
1376 SgenThreadPoolJob job;
1377 SgenObjectOperations *ops;
1380 } ScanThreadDataJob;
1383 job_scan_thread_data (void *worker_data_untyped, SgenThreadPoolJob *job)
1385 WorkerData *worker_data = worker_data_untyped;
1386 ScanThreadDataJob *job_data = (ScanThreadDataJob*)job;
1387 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (job_data->ops, sgen_workers_get_job_gray_queue (worker_data));
1389 sgen_client_scan_thread_data (job_data->heap_start, job_data->heap_end, TRUE, ctx);
1393 SgenThreadPoolJob job;
1394 SgenObjectOperations *ops;
1395 SgenPointerQueue *queue;
1396 } ScanFinalizerEntriesJob;
1399 job_scan_finalizer_entries (void *worker_data_untyped, SgenThreadPoolJob *job)
1401 WorkerData *worker_data = worker_data_untyped;
1402 ScanFinalizerEntriesJob *job_data = (ScanFinalizerEntriesJob*)job;
1403 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (job_data->ops, sgen_workers_get_job_gray_queue (worker_data));
1405 scan_finalizer_entries (job_data->queue, ctx);
1409 job_scan_major_mod_union_card_table (void *worker_data_untyped, SgenThreadPoolJob *job)
1411 WorkerData *worker_data = worker_data_untyped;
1412 ScanJob *job_data = (ScanJob*)job;
1413 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (job_data->ops, sgen_workers_get_job_gray_queue (worker_data));
1415 g_assert (concurrent_collection_in_progress);
1416 major_collector.scan_card_table (TRUE, ctx);
1420 job_scan_los_mod_union_card_table (void *worker_data_untyped, SgenThreadPoolJob *job)
1422 WorkerData *worker_data = worker_data_untyped;
1423 ScanJob *job_data = (ScanJob*)job;
1424 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (job_data->ops, sgen_workers_get_job_gray_queue (worker_data));
1426 g_assert (concurrent_collection_in_progress);
1427 sgen_los_scan_card_table (TRUE, ctx);
1431 init_gray_queue (void)
1433 if (sgen_collection_is_concurrent ())
1434 sgen_workers_init_distribute_gray_queue ();
1435 sgen_gray_object_queue_init (&gray_queue, NULL);
1439 enqueue_scan_from_roots_jobs (char *heap_start, char *heap_end, SgenObjectOperations *ops)
1441 ScanFromRegisteredRootsJob *scrrj;
1442 ScanThreadDataJob *stdj;
1443 ScanFinalizerEntriesJob *sfej;
1445 /* registered roots, this includes static fields */
1447 scrrj = (ScanFromRegisteredRootsJob*)sgen_thread_pool_job_alloc ("scan from registered roots normal", job_scan_from_registered_roots, sizeof (ScanFromRegisteredRootsJob));
1449 scrrj->heap_start = heap_start;
1450 scrrj->heap_end = heap_end;
1451 scrrj->root_type = ROOT_TYPE_NORMAL;
1452 sgen_workers_enqueue_job (&scrrj->job);
1454 scrrj = (ScanFromRegisteredRootsJob*)sgen_thread_pool_job_alloc ("scan from registered roots wbarrier", job_scan_from_registered_roots, sizeof (ScanFromRegisteredRootsJob));
1456 scrrj->heap_start = heap_start;
1457 scrrj->heap_end = heap_end;
1458 scrrj->root_type = ROOT_TYPE_WBARRIER;
1459 sgen_workers_enqueue_job (&scrrj->job);
1463 stdj = (ScanThreadDataJob*)sgen_thread_pool_job_alloc ("scan thread data", job_scan_thread_data, sizeof (ScanThreadDataJob));
1464 stdj->heap_start = heap_start;
1465 stdj->heap_end = heap_end;
1466 sgen_workers_enqueue_job (&stdj->job);
1468 /* Scan the list of objects ready for finalization. */
1470 sfej = (ScanFinalizerEntriesJob*)sgen_thread_pool_job_alloc ("scan finalizer entries", job_scan_finalizer_entries, sizeof (ScanFinalizerEntriesJob));
1471 sfej->queue = &fin_ready_queue;
1473 sgen_workers_enqueue_job (&sfej->job);
1475 sfej = (ScanFinalizerEntriesJob*)sgen_thread_pool_job_alloc ("scan critical finalizer entries", job_scan_finalizer_entries, sizeof (ScanFinalizerEntriesJob));
1476 sfej->queue = &critical_fin_queue;
1478 sgen_workers_enqueue_job (&sfej->job);
1482 * Perform a nursery collection.
1484 * Return whether any objects were late-pinned due to being out of memory.
1487 collect_nursery (SgenGrayQueue *unpin_queue, gboolean finish_up_concurrent_mark)
1489 gboolean needs_major;
1490 size_t max_garbage_amount;
1492 mword fragment_total;
1494 SgenObjectOperations *object_ops = &sgen_minor_collector.serial_ops;
1495 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (object_ops, &gray_queue);
1499 if (disable_minor_collections)
1502 TV_GETTIME (last_minor_collection_start_tv);
1503 atv = last_minor_collection_start_tv;
1505 binary_protocol_collection_begin (gc_stats.minor_gc_count, GENERATION_NURSERY);
1507 if (do_verify_nursery || do_dump_nursery_content)
1508 sgen_debug_verify_nursery (do_dump_nursery_content);
1510 current_collection_generation = GENERATION_NURSERY;
1512 SGEN_ASSERT (0, !sgen_collection_is_concurrent (), "Why is the nursery collection concurrent?");
1514 reset_pinned_from_failed_allocation ();
1516 check_scan_starts ();
1518 sgen_nursery_alloc_prepare_for_minor ();
1522 nursery_next = sgen_nursery_alloc_get_upper_alloc_bound ();
1523 /* FIXME: optimize later to use the higher address where an object can be present */
1524 nursery_next = MAX (nursery_next, sgen_get_nursery_end ());
1526 SGEN_LOG (1, "Start nursery collection %d %p-%p, size: %d", gc_stats.minor_gc_count, sgen_get_nursery_start (), nursery_next, (int)(nursery_next - sgen_get_nursery_start ()));
1527 max_garbage_amount = nursery_next - sgen_get_nursery_start ();
1528 g_assert (nursery_section->size >= max_garbage_amount);
1530 /* world must be stopped already */
1532 time_minor_pre_collection_fragment_clear += TV_ELAPSED (atv, btv);
1534 sgen_client_pre_collection_checks ();
1536 nursery_section->next_data = nursery_next;
1538 major_collector.start_nursery_collection ();
1540 sgen_memgov_minor_collection_start ();
1544 gc_stats.minor_gc_count ++;
1546 if (whole_heap_check_before_collection) {
1547 sgen_clear_nursery_fragments ();
1548 sgen_check_whole_heap (finish_up_concurrent_mark);
1550 if (consistency_check_at_minor_collection)
1551 sgen_check_consistency ();
1553 sgen_process_fin_stage_entries ();
1554 sgen_process_dislink_stage_entries ();
1556 /* pin from pinned handles */
1557 sgen_init_pinning ();
1558 sgen_client_binary_protocol_mark_start (GENERATION_NURSERY);
1559 pin_from_roots (sgen_get_nursery_start (), nursery_next, ctx);
1560 /* pin cemented objects */
1561 sgen_pin_cemented_objects ();
1562 /* identify pinned objects */
1563 sgen_optimize_pin_queue ();
1564 sgen_pinning_setup_section (nursery_section);
1566 pin_objects_in_nursery (FALSE, ctx);
1567 sgen_pinning_trim_queue_to_section (nursery_section);
1570 time_minor_pinning += TV_ELAPSED (btv, atv);
1571 SGEN_LOG (2, "Finding pinned pointers: %zd in %ld usecs", sgen_get_pinned_count (), TV_ELAPSED (btv, atv));
1572 SGEN_LOG (4, "Start scan with %zd pinned objects", sgen_get_pinned_count ());
1575 * FIXME: When we finish a concurrent collection we do a nursery collection first,
1576 * as part of which we scan the card table. Then, later, we scan the mod union
1577 * cardtable. We should only have to do one.
1579 sj = (ScanJob*)sgen_thread_pool_job_alloc ("scan remset", job_remembered_set_scan, sizeof (ScanJob));
1580 sj->ops = object_ops;
1581 sgen_workers_enqueue_job (&sj->job);
1583 /* we don't have complete write barrier yet, so we scan all the old generation sections */
1585 time_minor_scan_remsets += TV_ELAPSED (atv, btv);
1586 SGEN_LOG (2, "Old generation scan: %ld usecs", TV_ELAPSED (atv, btv));
1588 sgen_pin_stats_print_class_stats ();
1590 sgen_drain_gray_stack (-1, ctx);
1592 /* FIXME: Why do we do this at this specific, seemingly random, point? */
1593 sgen_client_collecting_minor (&fin_ready_queue, &critical_fin_queue);
1596 time_minor_scan_pinned += TV_ELAPSED (btv, atv);
1598 enqueue_scan_from_roots_jobs (sgen_get_nursery_start (), nursery_next, object_ops);
1601 time_minor_scan_roots += TV_ELAPSED (atv, btv);
1603 finish_gray_stack (GENERATION_NURSERY, ctx);
1606 time_minor_finish_gray_stack += TV_ELAPSED (btv, atv);
1607 sgen_client_binary_protocol_mark_end (GENERATION_NURSERY);
1609 if (objects_pinned) {
1610 sgen_optimize_pin_queue ();
1611 sgen_pinning_setup_section (nursery_section);
1614 /* walk the pin_queue, build up the fragment list of free memory, unmark
1615 * pinned objects as we go, memzero() the empty fragments so they are ready for the
1618 sgen_client_binary_protocol_reclaim_start (GENERATION_NURSERY);
1619 fragment_total = sgen_build_nursery_fragments (nursery_section, unpin_queue);
1620 if (!fragment_total)
1623 /* Clear TLABs for all threads */
1624 sgen_clear_tlabs ();
1626 sgen_client_binary_protocol_reclaim_end (GENERATION_NURSERY);
1628 time_minor_fragment_creation += TV_ELAPSED (atv, btv);
1629 SGEN_LOG (2, "Fragment creation: %ld usecs, %lu bytes available", TV_ELAPSED (atv, btv), (unsigned long)fragment_total);
1631 if (consistency_check_at_minor_collection)
1632 sgen_check_major_refs ();
1634 major_collector.finish_nursery_collection ();
1636 TV_GETTIME (last_minor_collection_end_tv);
1637 gc_stats.minor_gc_time += TV_ELAPSED (last_minor_collection_start_tv, last_minor_collection_end_tv);
1639 sgen_debug_dump_heap ("minor", gc_stats.minor_gc_count - 1, NULL);
1641 /* prepare the pin queue for the next collection */
1642 sgen_finish_pinning ();
1643 if (sgen_have_pending_finalizers ()) {
1644 SGEN_LOG (4, "Finalizer-thread wakeup");
1645 sgen_client_finalize_notify ();
1647 sgen_pin_stats_reset ();
1648 /* clear cemented hash */
1649 sgen_cement_clear_below_threshold ();
1651 g_assert (sgen_gray_object_queue_is_empty (&gray_queue));
1653 remset.finish_minor_collection ();
1655 check_scan_starts ();
1657 binary_protocol_flush_buffers (FALSE);
1659 sgen_memgov_minor_collection_end ();
1661 /*objects are late pinned because of lack of memory, so a major is a good call*/
1662 needs_major = objects_pinned > 0;
1663 current_collection_generation = -1;
1666 binary_protocol_collection_end (gc_stats.minor_gc_count - 1, GENERATION_NURSERY, 0, 0);
1668 if (check_nursery_objects_pinned && !sgen_minor_collector.is_split)
1669 sgen_check_nursery_objects_pinned (unpin_queue != NULL);
1675 scan_nursery_objects_callback (GCObject *obj, size_t size, ScanCopyContext *ctx)
1678 * This is called on all objects in the nursery, including pinned ones, so we need
1679 * to use sgen_obj_get_descriptor_safe(), which masks out the vtable tag bits.
1681 ctx->ops->scan_object (obj, sgen_obj_get_descriptor_safe (obj), ctx->queue);
1685 scan_nursery_objects (ScanCopyContext ctx)
1687 sgen_scan_area_with_callback (nursery_section->data, nursery_section->end_data,
1688 (IterateObjectCallbackFunc)scan_nursery_objects_callback, (void*)&ctx, FALSE);
1692 COPY_OR_MARK_FROM_ROOTS_SERIAL,
1693 COPY_OR_MARK_FROM_ROOTS_START_CONCURRENT,
1694 COPY_OR_MARK_FROM_ROOTS_FINISH_CONCURRENT
1695 } CopyOrMarkFromRootsMode;
1698 major_copy_or_mark_from_roots (size_t *old_next_pin_slot, CopyOrMarkFromRootsMode mode, gboolean scan_whole_nursery, SgenObjectOperations *object_ops)
1703 /* FIXME: only use these values for the precise scan
1704 * note that to_space pointers should be excluded anyway...
1706 char *heap_start = NULL;
1707 char *heap_end = (char*)-1;
1708 ScanCopyContext ctx = CONTEXT_FROM_OBJECT_OPERATIONS (object_ops, WORKERS_DISTRIBUTE_GRAY_QUEUE);
1709 gboolean concurrent = mode != COPY_OR_MARK_FROM_ROOTS_SERIAL;
1711 SGEN_ASSERT (0, !!concurrent == !!concurrent_collection_in_progress, "We've been called with the wrong mode.");
1713 if (scan_whole_nursery)
1714 SGEN_ASSERT (0, mode == COPY_OR_MARK_FROM_ROOTS_FINISH_CONCURRENT, "Scanning whole nursery only makes sense when we're finishing a concurrent collection.");
1717 /*This cleans up unused fragments */
1718 sgen_nursery_allocator_prepare_for_pinning ();
1720 if (do_concurrent_checks)
1721 sgen_debug_check_nursery_is_clean ();
1723 /* The concurrent collector doesn't touch the nursery. */
1724 sgen_nursery_alloc_prepare_for_major ();
1731 /* Pinning depends on this */
1732 sgen_clear_nursery_fragments ();
1734 if (whole_heap_check_before_collection)
1735 sgen_check_whole_heap (mode == COPY_OR_MARK_FROM_ROOTS_FINISH_CONCURRENT);
1738 time_major_pre_collection_fragment_clear += TV_ELAPSED (atv, btv);
1740 if (!sgen_collection_is_concurrent ())
1741 nursery_section->next_data = sgen_get_nursery_end ();
1742 /* we should also coalesce scanning from sections close to each other
1743 * and deal with pointers outside of the sections later.
1748 sgen_client_pre_collection_checks ();
1751 /* Remsets are not useful for a major collection */
1752 remset.clear_cards ();
1755 sgen_process_fin_stage_entries ();
1756 sgen_process_dislink_stage_entries ();
1759 sgen_init_pinning ();
1760 SGEN_LOG (6, "Collecting pinned addresses");
1761 pin_from_roots ((void*)lowest_heap_address, (void*)highest_heap_address, ctx);
1763 if (mode != COPY_OR_MARK_FROM_ROOTS_START_CONCURRENT) {
1764 if (major_collector.is_concurrent) {
1766 * The concurrent major collector cannot evict
1767 * yet, so we need to pin cemented objects to
1768 * not break some asserts.
1770 * FIXME: We could evict now!
1772 sgen_pin_cemented_objects ();
1776 sgen_optimize_pin_queue ();
1778 sgen_client_collecting_major_1 ();
1781 * pin_queue now contains all candidate pointers, sorted and
1782 * uniqued. We must do two passes now to figure out which
1783 * objects are pinned.
1785 * The first is to find within the pin_queue the area for each
1786 * section. This requires that the pin_queue be sorted. We
1787 * also process the LOS objects and pinned chunks here.
1789 * The second, destructive, pass is to reduce the section
1790 * areas to pointers to the actually pinned objects.
1792 SGEN_LOG (6, "Pinning from sections");
1793 /* first pass for the sections */
1794 sgen_find_section_pin_queue_start_end (nursery_section);
1795 /* identify possible pointers to the insize of large objects */
1796 SGEN_LOG (6, "Pinning from large objects");
1797 for (bigobj = los_object_list; bigobj; bigobj = bigobj->next) {
1799 if (sgen_find_optimized_pin_queue_area ((char*)bigobj->data, (char*)bigobj->data + sgen_los_object_size (bigobj), &dummy, &dummy)) {
1800 binary_protocol_pin (bigobj->data, (gpointer)LOAD_VTABLE (bigobj->data), safe_object_get_size (bigobj->data));
1802 if (sgen_los_object_is_pinned (bigobj->data)) {
1803 SGEN_ASSERT (0, mode == COPY_OR_MARK_FROM_ROOTS_FINISH_CONCURRENT, "LOS objects can only be pinned here after concurrent marking.");
1806 sgen_los_pin_object (bigobj->data);
1807 if (SGEN_OBJECT_HAS_REFERENCES (bigobj->data))
1808 GRAY_OBJECT_ENQUEUE (WORKERS_DISTRIBUTE_GRAY_QUEUE, bigobj->data, sgen_obj_get_descriptor ((GCObject*)bigobj->data));
1809 sgen_pin_stats_register_object (bigobj->data, safe_object_get_size (bigobj->data));
1810 SGEN_LOG (6, "Marked large object %p (%s) size: %lu from roots", bigobj->data,
1811 sgen_client_vtable_get_name (SGEN_LOAD_VTABLE (bigobj->data)),
1812 (unsigned long)sgen_los_object_size (bigobj));
1814 sgen_client_pinned_los_object (bigobj->data);
1817 /* second pass for the sections */
1820 * Concurrent mark never follows references into the nursery. In the start and
1821 * finish pauses we must scan live nursery objects, though.
1823 * In the finish pause we do this conservatively by scanning all nursery objects.
1824 * Previously we would only scan pinned objects here. We assumed that all objects
1825 * that were pinned during the nursery collection immediately preceding this finish
1826 * mark would be pinned again here. Due to the way we get the stack end for the GC
1827 * thread, however, that's not necessarily the case: we scan part of the stack used
1828 * by the GC itself, which changes constantly, so pinning isn't entirely
1831 * The split nursery also complicates things because non-pinned objects can survive
1832 * in the nursery. That's why we need to do a full scan of the nursery for it, too.
1834 * In the future we shouldn't do a preceding nursery collection at all and instead
1835 * do the finish pause with promotion from the nursery.
1837 * A further complication arises when we have late-pinned objects from the preceding
1838 * nursery collection. Those are the result of being out of memory when trying to
1839 * evacuate objects. They won't be found from the roots, so we just scan the whole
1842 * Non-concurrent mark evacuates from the nursery, so it's
1843 * sufficient to just scan pinned nursery objects.
1845 if (scan_whole_nursery || mode == COPY_OR_MARK_FROM_ROOTS_FINISH_CONCURRENT || (concurrent && sgen_minor_collector.is_split)) {
1846 scan_nursery_objects (ctx);
1848 pin_objects_in_nursery (concurrent, ctx);
1849 if (check_nursery_objects_pinned && !sgen_minor_collector.is_split)
1850 sgen_check_nursery_objects_pinned (mode != COPY_OR_MARK_FROM_ROOTS_START_CONCURRENT);
1853 major_collector.pin_objects (WORKERS_DISTRIBUTE_GRAY_QUEUE);
1854 if (old_next_pin_slot)
1855 *old_next_pin_slot = sgen_get_pinned_count ();
1858 time_major_pinning += TV_ELAPSED (atv, btv);
1859 SGEN_LOG (2, "Finding pinned pointers: %zd in %ld usecs", sgen_get_pinned_count (), TV_ELAPSED (atv, btv));
1860 SGEN_LOG (4, "Start scan with %zd pinned objects", sgen_get_pinned_count ());
1862 major_collector.init_to_space ();
1865 * The concurrent collector doesn't move objects, neither on
1866 * the major heap nor in the nursery, so we can mark even
1867 * before pinning has finished. For the non-concurrent
1868 * collector we start the workers after pinning.
1870 if (mode != COPY_OR_MARK_FROM_ROOTS_SERIAL) {
1871 SGEN_ASSERT (0, sgen_workers_all_done (), "Why are the workers not done when we start or finish a major collection?");
1872 sgen_workers_start_all_workers (object_ops);
1873 gray_queue_enable_redirect (WORKERS_DISTRIBUTE_GRAY_QUEUE);
1876 #ifdef SGEN_DEBUG_INTERNAL_ALLOC
1877 main_gc_thread = mono_native_thread_self ();
1880 sgen_client_collecting_major_2 ();
1883 time_major_scan_pinned += TV_ELAPSED (btv, atv);
1885 sgen_client_collecting_major_3 (&fin_ready_queue, &critical_fin_queue);
1888 * FIXME: is this the right context? It doesn't seem to contain a copy function
1889 * unless we're concurrent.
1891 enqueue_scan_from_roots_jobs (heap_start, heap_end, object_ops);
1894 time_major_scan_roots += TV_ELAPSED (atv, btv);
1896 if (mode == COPY_OR_MARK_FROM_ROOTS_FINISH_CONCURRENT) {
1899 /* Mod union card table */
1900 sj = (ScanJob*)sgen_thread_pool_job_alloc ("scan mod union cardtable", job_scan_major_mod_union_card_table, sizeof (ScanJob));
1901 sj->ops = object_ops;
1902 sgen_workers_enqueue_job (&sj->job);
1904 sj = (ScanJob*)sgen_thread_pool_job_alloc ("scan LOS mod union cardtable", job_scan_los_mod_union_card_table, sizeof (ScanJob));
1905 sj->ops = object_ops;
1906 sgen_workers_enqueue_job (&sj->job);
1909 time_major_scan_mod_union += TV_ELAPSED (btv, atv);
1912 sgen_pin_stats_print_class_stats ();
1916 major_finish_copy_or_mark (void)
1918 if (!concurrent_collection_in_progress)
1922 * Prepare the pin queue for the next collection. Since pinning runs on the worker
1923 * threads we must wait for the jobs to finish before we can reset it.
1925 sgen_workers_wait_for_jobs_finished ();
1926 sgen_finish_pinning ();
1928 sgen_pin_stats_reset ();
1930 if (do_concurrent_checks)
1931 sgen_debug_check_nursery_is_clean ();
1935 major_start_collection (gboolean concurrent, size_t *old_next_pin_slot)
1937 SgenObjectOperations *object_ops;
1939 binary_protocol_collection_begin (gc_stats.major_gc_count, GENERATION_OLD);
1941 current_collection_generation = GENERATION_OLD;
1943 g_assert (sgen_section_gray_queue_is_empty (sgen_workers_get_distribute_section_gray_queue ()));
1945 sgen_cement_reset ();
1948 g_assert (major_collector.is_concurrent);
1949 concurrent_collection_in_progress = TRUE;
1951 object_ops = &major_collector.major_ops_concurrent_start;
1953 object_ops = &major_collector.major_ops_serial;
1956 reset_pinned_from_failed_allocation ();
1958 sgen_memgov_major_collection_start ();
1960 //count_ref_nonref_objs ();
1961 //consistency_check ();
1963 check_scan_starts ();
1966 SGEN_LOG (1, "Start major collection %d", gc_stats.major_gc_count);
1967 gc_stats.major_gc_count ++;
1969 if (major_collector.start_major_collection)
1970 major_collector.start_major_collection ();
1972 major_copy_or_mark_from_roots (old_next_pin_slot, concurrent ? COPY_OR_MARK_FROM_ROOTS_START_CONCURRENT : COPY_OR_MARK_FROM_ROOTS_SERIAL, FALSE, object_ops);
1973 major_finish_copy_or_mark ();
1977 major_finish_collection (const char *reason, size_t old_next_pin_slot, gboolean forced, gboolean scan_whole_nursery)
1979 ScannedObjectCounts counts;
1980 SgenObjectOperations *object_ops;
1986 if (concurrent_collection_in_progress) {
1987 object_ops = &major_collector.major_ops_concurrent_finish;
1989 major_copy_or_mark_from_roots (NULL, COPY_OR_MARK_FROM_ROOTS_FINISH_CONCURRENT, scan_whole_nursery, object_ops);
1991 major_finish_copy_or_mark ();
1993 sgen_workers_join ();
1995 SGEN_ASSERT (0, sgen_gray_object_queue_is_empty (&gray_queue), "Why is the gray queue not empty after workers have finished working?");
1997 #ifdef SGEN_DEBUG_INTERNAL_ALLOC
1998 main_gc_thread = NULL;
2001 if (do_concurrent_checks)
2002 sgen_debug_check_nursery_is_clean ();
2004 SGEN_ASSERT (0, !scan_whole_nursery, "scan_whole_nursery only applies to concurrent collections");
2005 object_ops = &major_collector.major_ops_serial;
2009 * The workers have stopped so we need to finish gray queue
2010 * work that might result from finalization in the main GC
2011 * thread. Redirection must therefore be turned off.
2013 sgen_gray_object_queue_disable_alloc_prepare (&gray_queue);
2014 g_assert (sgen_section_gray_queue_is_empty (sgen_workers_get_distribute_section_gray_queue ()));
2016 /* all the objects in the heap */
2017 finish_gray_stack (GENERATION_OLD, CONTEXT_FROM_OBJECT_OPERATIONS (object_ops, &gray_queue));
2019 time_major_finish_gray_stack += TV_ELAPSED (btv, atv);
2021 SGEN_ASSERT (0, sgen_workers_all_done (), "Can't have workers working after joining");
2023 if (objects_pinned) {
2024 g_assert (!concurrent_collection_in_progress);
2027 * This is slow, but we just OOM'd.
2029 * See comment at `sgen_pin_queue_clear_discarded_entries` for how the pin
2030 * queue is laid out at this point.
2032 sgen_pin_queue_clear_discarded_entries (nursery_section, old_next_pin_slot);
2034 * We need to reestablish all pinned nursery objects in the pin queue
2035 * because they're needed for fragment creation. Unpinning happens by
2036 * walking the whole queue, so it's not necessary to reestablish where major
2037 * heap block pins are - all we care is that they're still in there
2040 sgen_optimize_pin_queue ();
2041 sgen_find_section_pin_queue_start_end (nursery_section);
2045 reset_heap_boundaries ();
2046 sgen_update_heap_boundaries ((mword)sgen_get_nursery_start (), (mword)sgen_get_nursery_end ());
2048 if (!concurrent_collection_in_progress) {
2049 /* walk the pin_queue, build up the fragment list of free memory, unmark
2050 * pinned objects as we go, memzero() the empty fragments so they are ready for the
2053 if (!sgen_build_nursery_fragments (nursery_section, NULL))
2056 /* prepare the pin queue for the next collection */
2057 sgen_finish_pinning ();
2059 /* Clear TLABs for all threads */
2060 sgen_clear_tlabs ();
2062 sgen_pin_stats_reset ();
2065 sgen_cement_clear_below_threshold ();
2067 if (check_mark_bits_after_major_collection)
2068 sgen_check_heap_marked (concurrent_collection_in_progress);
2071 time_major_fragment_creation += TV_ELAPSED (atv, btv);
2073 binary_protocol_sweep_begin (GENERATION_OLD, !major_collector.sweeps_lazily);
2076 time_major_free_bigobjs += TV_ELAPSED (btv, atv);
2081 time_major_los_sweep += TV_ELAPSED (atv, btv);
2083 major_collector.sweep ();
2085 binary_protocol_sweep_end (GENERATION_OLD, !major_collector.sweeps_lazily);
2088 time_major_sweep += TV_ELAPSED (btv, atv);
2090 sgen_debug_dump_heap ("major", gc_stats.major_gc_count - 1, reason);
2092 if (sgen_have_pending_finalizers ()) {
2093 SGEN_LOG (4, "Finalizer-thread wakeup");
2094 sgen_client_finalize_notify ();
2097 g_assert (sgen_gray_object_queue_is_empty (&gray_queue));
2099 sgen_memgov_major_collection_end (forced);
2100 current_collection_generation = -1;
2102 memset (&counts, 0, sizeof (ScannedObjectCounts));
2103 major_collector.finish_major_collection (&counts);
2105 g_assert (sgen_section_gray_queue_is_empty (sgen_workers_get_distribute_section_gray_queue ()));
2107 SGEN_ASSERT (0, sgen_workers_all_done (), "Can't have workers working after major collection has finished");
2108 if (concurrent_collection_in_progress)
2109 concurrent_collection_in_progress = FALSE;
2111 check_scan_starts ();
2113 binary_protocol_flush_buffers (FALSE);
2115 //consistency_check ();
2117 binary_protocol_collection_end (gc_stats.major_gc_count - 1, GENERATION_OLD, counts.num_scanned_objects, counts.num_unique_scanned_objects);
2121 major_do_collection (const char *reason, gboolean forced)
2123 TV_DECLARE (time_start);
2124 TV_DECLARE (time_end);
2125 size_t old_next_pin_slot;
2127 if (disable_major_collections)
2130 if (major_collector.get_and_reset_num_major_objects_marked) {
2131 long long num_marked = major_collector.get_and_reset_num_major_objects_marked ();
2132 g_assert (!num_marked);
2135 /* world must be stopped already */
2136 TV_GETTIME (time_start);
2138 major_start_collection (FALSE, &old_next_pin_slot);
2139 major_finish_collection (reason, old_next_pin_slot, forced, FALSE);
2141 TV_GETTIME (time_end);
2142 gc_stats.major_gc_time += TV_ELAPSED (time_start, time_end);
2144 /* FIXME: also report this to the user, preferably in gc-end. */
2145 if (major_collector.get_and_reset_num_major_objects_marked)
2146 major_collector.get_and_reset_num_major_objects_marked ();
2148 return bytes_pinned_from_failed_allocation > 0;
2152 major_start_concurrent_collection (const char *reason)
2154 TV_DECLARE (time_start);
2155 TV_DECLARE (time_end);
2156 long long num_objects_marked;
2158 if (disable_major_collections)
2161 TV_GETTIME (time_start);
2162 SGEN_TV_GETTIME (time_major_conc_collection_start);
2164 num_objects_marked = major_collector.get_and_reset_num_major_objects_marked ();
2165 g_assert (num_objects_marked == 0);
2167 binary_protocol_concurrent_start ();
2169 // FIXME: store reason and pass it when finishing
2170 major_start_collection (TRUE, NULL);
2172 gray_queue_redirect (&gray_queue);
2174 num_objects_marked = major_collector.get_and_reset_num_major_objects_marked ();
2176 TV_GETTIME (time_end);
2177 gc_stats.major_gc_time += TV_ELAPSED (time_start, time_end);
2179 current_collection_generation = -1;
2183 * Returns whether the major collection has finished.
2186 major_should_finish_concurrent_collection (void)
2188 SGEN_ASSERT (0, sgen_gray_object_queue_is_empty (&gray_queue), "Why is the gray queue not empty before we have started doing anything?");
2189 return sgen_workers_all_done ();
2193 major_update_concurrent_collection (void)
2195 TV_DECLARE (total_start);
2196 TV_DECLARE (total_end);
2198 TV_GETTIME (total_start);
2200 binary_protocol_concurrent_update ();
2202 major_collector.update_cardtable_mod_union ();
2203 sgen_los_update_cardtable_mod_union ();
2205 TV_GETTIME (total_end);
2206 gc_stats.major_gc_time += TV_ELAPSED (total_start, total_end);
2210 major_finish_concurrent_collection (gboolean forced)
2212 TV_DECLARE (total_start);
2213 TV_DECLARE (total_end);
2214 gboolean late_pinned;
2215 SgenGrayQueue unpin_queue;
2216 memset (&unpin_queue, 0, sizeof (unpin_queue));
2218 TV_GETTIME (total_start);
2220 binary_protocol_concurrent_finish ();
2223 * The major collector can add global remsets which are processed in the finishing
2224 * nursery collection, below. That implies that the workers must have finished
2225 * marking before the nursery collection is allowed to run, otherwise we might miss
2228 sgen_workers_wait ();
2230 SGEN_TV_GETTIME (time_major_conc_collection_end);
2231 gc_stats.major_gc_time_concurrent += SGEN_TV_ELAPSED (time_major_conc_collection_start, time_major_conc_collection_end);
2233 major_collector.update_cardtable_mod_union ();
2234 sgen_los_update_cardtable_mod_union ();
2236 late_pinned = collect_nursery (&unpin_queue, TRUE);
2238 if (mod_union_consistency_check)
2239 sgen_check_mod_union_consistency ();
2241 current_collection_generation = GENERATION_OLD;
2242 major_finish_collection ("finishing", -1, forced, late_pinned);
2244 if (whole_heap_check_before_collection)
2245 sgen_check_whole_heap (FALSE);
2247 unpin_objects_from_queue (&unpin_queue);
2248 sgen_gray_object_queue_deinit (&unpin_queue);
2250 TV_GETTIME (total_end);
2251 gc_stats.major_gc_time += TV_ELAPSED (total_start, total_end) - TV_ELAPSED (last_minor_collection_start_tv, last_minor_collection_end_tv);
2253 current_collection_generation = -1;
2257 * Ensure an allocation request for @size will succeed by freeing enough memory.
2259 * LOCKING: The GC lock MUST be held.
2262 sgen_ensure_free_space (size_t size)
2264 int generation_to_collect = -1;
2265 const char *reason = NULL;
2267 if (size > SGEN_MAX_SMALL_OBJ_SIZE) {
2268 if (sgen_need_major_collection (size)) {
2269 reason = "LOS overflow";
2270 generation_to_collect = GENERATION_OLD;
2273 if (degraded_mode) {
2274 if (sgen_need_major_collection (size)) {
2275 reason = "Degraded mode overflow";
2276 generation_to_collect = GENERATION_OLD;
2278 } else if (sgen_need_major_collection (size)) {
2279 reason = "Minor allowance";
2280 generation_to_collect = GENERATION_OLD;
2282 generation_to_collect = GENERATION_NURSERY;
2283 reason = "Nursery full";
2287 if (generation_to_collect == -1) {
2288 if (concurrent_collection_in_progress && sgen_workers_all_done ()) {
2289 generation_to_collect = GENERATION_OLD;
2290 reason = "Finish concurrent collection";
2294 if (generation_to_collect == -1)
2296 sgen_perform_collection (size, generation_to_collect, reason, FALSE);
2300 * LOCKING: Assumes the GC lock is held.
2303 sgen_perform_collection (size_t requested_size, int generation_to_collect, const char *reason, gboolean wait_to_finish)
2305 TV_DECLARE (gc_start);
2306 TV_DECLARE (gc_end);
2307 TV_DECLARE (gc_total_start);
2308 TV_DECLARE (gc_total_end);
2309 GGTimingInfo infos [2];
2310 int overflow_generation_to_collect = -1;
2311 int oldest_generation_collected = generation_to_collect;
2312 const char *overflow_reason = NULL;
2314 binary_protocol_collection_requested (generation_to_collect, requested_size, wait_to_finish ? 1 : 0);
2316 SGEN_ASSERT (0, generation_to_collect == GENERATION_NURSERY || generation_to_collect == GENERATION_OLD, "What generation is this?");
2318 TV_GETTIME (gc_start);
2320 sgen_stop_world (generation_to_collect);
2322 TV_GETTIME (gc_total_start);
2324 if (concurrent_collection_in_progress) {
2326 * We update the concurrent collection. If it finished, we're done. If
2327 * not, and we've been asked to do a nursery collection, we do that.
2329 gboolean finish = major_should_finish_concurrent_collection () || (wait_to_finish && generation_to_collect == GENERATION_OLD);
2332 major_finish_concurrent_collection (wait_to_finish);
2333 oldest_generation_collected = GENERATION_OLD;
2335 sgen_workers_signal_start_nursery_collection_and_wait ();
2337 major_update_concurrent_collection ();
2338 if (generation_to_collect == GENERATION_NURSERY)
2339 collect_nursery (NULL, FALSE);
2341 sgen_workers_signal_finish_nursery_collection ();
2348 * If we've been asked to do a major collection, and the major collector wants to
2349 * run synchronously (to evacuate), we set the flag to do that.
2351 if (generation_to_collect == GENERATION_OLD &&
2352 allow_synchronous_major &&
2353 major_collector.want_synchronous_collection &&
2354 *major_collector.want_synchronous_collection) {
2355 wait_to_finish = TRUE;
2358 SGEN_ASSERT (0, !concurrent_collection_in_progress, "Why did this not get handled above?");
2361 * There's no concurrent collection in progress. Collect the generation we're asked
2362 * to collect. If the major collector is concurrent and we're not forced to wait,
2363 * start a concurrent collection.
2365 // FIXME: extract overflow reason
2366 if (generation_to_collect == GENERATION_NURSERY) {
2367 if (collect_nursery (NULL, FALSE)) {
2368 overflow_generation_to_collect = GENERATION_OLD;
2369 overflow_reason = "Minor overflow";
2372 if (major_collector.is_concurrent && !wait_to_finish) {
2373 collect_nursery (NULL, FALSE);
2374 major_start_concurrent_collection (reason);
2375 // FIXME: set infos[0] properly
2379 if (major_do_collection (reason, wait_to_finish)) {
2380 overflow_generation_to_collect = GENERATION_NURSERY;
2381 overflow_reason = "Excessive pinning";
2385 TV_GETTIME (gc_end);
2387 memset (infos, 0, sizeof (infos));
2388 infos [0].generation = generation_to_collect;
2389 infos [0].reason = reason;
2390 infos [0].is_overflow = FALSE;
2391 infos [1].generation = -1;
2392 infos [0].total_time = SGEN_TV_ELAPSED (gc_start, gc_end);
2394 SGEN_ASSERT (0, !concurrent_collection_in_progress, "Why did this not get handled above?");
2396 if (overflow_generation_to_collect != -1) {
2398 * We need to do an overflow collection, either because we ran out of memory
2399 * or the nursery is fully pinned.
2402 infos [1].generation = overflow_generation_to_collect;
2403 infos [1].reason = overflow_reason;
2404 infos [1].is_overflow = TRUE;
2407 if (overflow_generation_to_collect == GENERATION_NURSERY)
2408 collect_nursery (NULL, FALSE);
2410 major_do_collection (overflow_reason, wait_to_finish);
2412 TV_GETTIME (gc_end);
2413 infos [1].total_time = SGEN_TV_ELAPSED (gc_start, gc_end);
2415 oldest_generation_collected = MAX (oldest_generation_collected, overflow_generation_to_collect);
2418 SGEN_LOG (2, "Heap size: %lu, LOS size: %lu", (unsigned long)sgen_gc_get_total_heap_allocation (), (unsigned long)los_memory_usage);
2420 /* this also sets the proper pointers for the next allocation */
2421 if (generation_to_collect == GENERATION_NURSERY && !sgen_can_alloc_size (requested_size)) {
2422 /* TypeBuilder and MonoMethod are killing mcs with fragmentation */
2423 SGEN_LOG (1, "nursery collection didn't find enough room for %zd alloc (%zd pinned)", requested_size, sgen_get_pinned_count ());
2424 sgen_dump_pin_queue ();
2429 g_assert (sgen_gray_object_queue_is_empty (&gray_queue));
2431 TV_GETTIME (gc_total_end);
2432 time_max = MAX (time_max, TV_ELAPSED (gc_total_start, gc_total_end));
2434 sgen_restart_world (oldest_generation_collected, infos);
2438 * ######################################################################
2439 * ######## Memory allocation from the OS
2440 * ######################################################################
2441 * This section of code deals with getting memory from the OS and
2442 * allocating memory for GC-internal data structures.
2443 * Internal memory can be handled with a freelist for small objects.
2449 G_GNUC_UNUSED static void
2450 report_internal_mem_usage (void)
2452 printf ("Internal memory usage:\n");
2453 sgen_report_internal_mem_usage ();
2454 printf ("Pinned memory usage:\n");
2455 major_collector.report_pinned_memory_usage ();
2459 * ######################################################################
2460 * ######## Finalization support
2461 * ######################################################################
2465 * If the object has been forwarded it means it's still referenced from a root.
2466 * If it is pinned it's still alive as well.
2467 * A LOS object is only alive if we have pinned it.
2468 * Return TRUE if @obj is ready to be finalized.
2470 static inline gboolean
2471 sgen_is_object_alive (GCObject *object)
2473 if (ptr_in_nursery (object))
2474 return sgen_nursery_is_object_alive (object);
2476 return sgen_major_is_object_alive (object);
2480 * This function returns true if @object is either alive and belongs to the
2481 * current collection - major collections are full heap, so old gen objects
2482 * are never alive during a minor collection.
2485 sgen_is_object_alive_and_on_current_collection (GCObject *object)
2487 if (ptr_in_nursery (object))
2488 return sgen_nursery_is_object_alive (object);
2490 if (current_collection_generation == GENERATION_NURSERY)
2493 return sgen_major_is_object_alive (object);
2498 sgen_gc_is_object_ready_for_finalization (GCObject *object)
2500 return !sgen_is_object_alive (object);
2504 sgen_queue_finalization_entry (GCObject *obj)
2506 gboolean critical = sgen_client_object_has_critical_finalizer (obj);
2508 sgen_pointer_queue_add (critical ? &critical_fin_queue : &fin_ready_queue, obj);
2510 sgen_client_object_queued_for_finalization (obj);
2514 sgen_object_is_live (GCObject *obj)
2516 return sgen_is_object_alive_and_on_current_collection (obj);
2520 * `System.GC.WaitForPendingFinalizers` first checks `sgen_have_pending_finalizers()` to
2521 * determine whether it can exit quickly. The latter must therefore only return FALSE if
2522 * all finalizers have really finished running.
2524 * `sgen_gc_invoke_finalizers()` first dequeues a finalizable object, and then finalizes it.
2525 * This means that just checking whether the queues are empty leaves the possibility that an
2526 * object might have been dequeued but not yet finalized. That's why we need the additional
2527 * flag `pending_unqueued_finalizer`.
2530 static volatile gboolean pending_unqueued_finalizer = FALSE;
2533 sgen_gc_invoke_finalizers (void)
2537 g_assert (!pending_unqueued_finalizer);
2539 /* FIXME: batch to reduce lock contention */
2540 while (sgen_have_pending_finalizers ()) {
2546 * We need to set `pending_unqueued_finalizer` before dequeing the
2547 * finalizable object.
2549 if (!sgen_pointer_queue_is_empty (&fin_ready_queue)) {
2550 pending_unqueued_finalizer = TRUE;
2551 mono_memory_write_barrier ();
2552 obj = sgen_pointer_queue_pop (&fin_ready_queue);
2553 } else if (!sgen_pointer_queue_is_empty (&critical_fin_queue)) {
2554 pending_unqueued_finalizer = TRUE;
2555 mono_memory_write_barrier ();
2556 obj = sgen_pointer_queue_pop (&critical_fin_queue);
2562 SGEN_LOG (7, "Finalizing object %p (%s)", obj, sgen_client_vtable_get_name (SGEN_LOAD_VTABLE (obj)));
2570 /* the object is on the stack so it is pinned */
2571 /*g_print ("Calling finalizer for object: %p (%s)\n", obj, sgen_client_object_safe_name (obj));*/
2572 sgen_client_run_finalize (obj);
2575 if (pending_unqueued_finalizer) {
2576 mono_memory_write_barrier ();
2577 pending_unqueued_finalizer = FALSE;
2584 sgen_have_pending_finalizers (void)
2586 return pending_unqueued_finalizer || !sgen_pointer_queue_is_empty (&fin_ready_queue) || !sgen_pointer_queue_is_empty (&critical_fin_queue);
2590 * ######################################################################
2591 * ######## registered roots support
2592 * ######################################################################
2596 * We do not coalesce roots.
2599 sgen_register_root (char *start, size_t size, SgenDescriptor descr, int root_type)
2601 RootRecord new_root;
2604 for (i = 0; i < ROOT_TYPE_NUM; ++i) {
2605 RootRecord *root = sgen_hash_table_lookup (&roots_hash [i], start);
2606 /* we allow changing the size and the descriptor (for thread statics etc) */
2608 size_t old_size = root->end_root - start;
2609 root->end_root = start + size;
2610 SGEN_ASSERT (0, !!root->root_desc == !!descr, "Can't change whether a root is precise or conservative.");
2611 root->root_desc = descr;
2613 roots_size -= old_size;
2619 new_root.end_root = start + size;
2620 new_root.root_desc = descr;
2622 sgen_hash_table_replace (&roots_hash [root_type], start, &new_root, NULL);
2625 SGEN_LOG (3, "Added root for range: %p-%p, descr: %llx (%d/%d bytes)", start, new_root.end_root, descr, (int)size, (int)roots_size);
2632 sgen_deregister_root (char* addr)
2638 for (root_type = 0; root_type < ROOT_TYPE_NUM; ++root_type) {
2639 if (sgen_hash_table_remove (&roots_hash [root_type], addr, &root))
2640 roots_size -= (root.end_root - addr);
2646 * ######################################################################
2647 * ######## Thread handling (stop/start code)
2648 * ######################################################################
2652 sgen_get_current_collection_generation (void)
2654 return current_collection_generation;
2658 sgen_thread_register (SgenThreadInfo* info, void *stack_bottom_fallback)
2660 #ifndef HAVE_KW_THREAD
2661 info->tlab_start = info->tlab_next = info->tlab_temp_end = info->tlab_real_end = NULL;
2664 sgen_init_tlab_info (info);
2666 sgen_client_thread_register (info, stack_bottom_fallback);
2672 sgen_thread_unregister (SgenThreadInfo *p)
2674 sgen_client_thread_unregister (p);
2678 * ######################################################################
2679 * ######## Write barriers
2680 * ######################################################################
2684 * Note: the write barriers first do the needed GC work and then do the actual store:
2685 * this way the value is visible to the conservative GC scan after the write barrier
2686 * itself. If a GC interrupts the barrier in the middle, value will be kept alive by
2687 * the conservative scan, otherwise by the remembered set scan.
2691 mono_gc_wbarrier_arrayref_copy (gpointer dest_ptr, gpointer src_ptr, int count)
2693 HEAVY_STAT (++stat_wbarrier_arrayref_copy);
2694 /*This check can be done without taking a lock since dest_ptr array is pinned*/
2695 if (ptr_in_nursery (dest_ptr) || count <= 0) {
2696 mono_gc_memmove_aligned (dest_ptr, src_ptr, count * sizeof (gpointer));
2700 #ifdef SGEN_HEAVY_BINARY_PROTOCOL
2701 if (binary_protocol_is_heavy_enabled ()) {
2703 for (i = 0; i < count; ++i) {
2704 gpointer dest = (gpointer*)dest_ptr + i;
2705 gpointer obj = *((gpointer*)src_ptr + i);
2707 binary_protocol_wbarrier (dest, obj, (gpointer)LOAD_VTABLE (obj));
2712 remset.wbarrier_arrayref_copy (dest_ptr, src_ptr, count);
2716 mono_gc_wbarrier_generic_nostore (gpointer ptr)
2720 HEAVY_STAT (++stat_wbarrier_generic_store);
2722 sgen_client_wbarrier_generic_nostore_check (ptr);
2724 obj = *(gpointer*)ptr;
2726 binary_protocol_wbarrier (ptr, obj, (gpointer)LOAD_VTABLE (obj));
2729 * We need to record old->old pointer locations for the
2730 * concurrent collector.
2732 if (!ptr_in_nursery (obj) && !concurrent_collection_in_progress) {
2733 SGEN_LOG (8, "Skipping remset at %p", ptr);
2737 SGEN_LOG (8, "Adding remset at %p", ptr);
2739 remset.wbarrier_generic_nostore (ptr);
2743 mono_gc_wbarrier_generic_store (gpointer ptr, GCObject* value)
2745 SGEN_LOG (8, "Wbarrier store at %p to %p (%s)", ptr, value, value ? sgen_client_vtable_get_name (SGEN_LOAD_VTABLE (value)) : "null");
2746 SGEN_UPDATE_REFERENCE_ALLOW_NULL (ptr, value);
2747 if (ptr_in_nursery (value))
2748 mono_gc_wbarrier_generic_nostore (ptr);
2749 sgen_dummy_use (value);
2752 /* Same as mono_gc_wbarrier_generic_store () but performs the store
2753 * as an atomic operation with release semantics.
2756 mono_gc_wbarrier_generic_store_atomic (gpointer ptr, GCObject *value)
2758 HEAVY_STAT (++stat_wbarrier_generic_store_atomic);
2760 SGEN_LOG (8, "Wbarrier atomic store at %p to %p (%s)", ptr, value, value ? sgen_client_vtable_get_name (SGEN_LOAD_VTABLE (value)) : "null");
2762 InterlockedWritePointer (ptr, value);
2764 if (ptr_in_nursery (value))
2765 mono_gc_wbarrier_generic_nostore (ptr);
2767 sgen_dummy_use (value);
2771 sgen_wbarrier_value_copy_bitmap (gpointer _dest, gpointer _src, int size, unsigned bitmap)
2773 GCObject **dest = _dest;
2774 GCObject **src = _src;
2778 mono_gc_wbarrier_generic_store (dest, *src);
2783 size -= SIZEOF_VOID_P;
2789 * ######################################################################
2790 * ######## Other mono public interface functions.
2791 * ######################################################################
2795 sgen_gc_collect (int generation)
2800 sgen_perform_collection (0, generation, "user request", TRUE);
2805 sgen_gc_collection_count (int generation)
2807 if (generation == 0)
2808 return gc_stats.minor_gc_count;
2809 return gc_stats.major_gc_count;
2813 sgen_gc_get_used_size (void)
2817 tot = los_memory_usage;
2818 tot += nursery_section->next_data - nursery_section->data;
2819 tot += major_collector.get_used_size ();
2820 /* FIXME: account for pinned objects */
2826 sgen_weak_link_get (void **link_addr)
2828 void * volatile *link_addr_volatile;
2832 link_addr_volatile = link_addr;
2833 ptr = (void*)*link_addr_volatile;
2835 * At this point we have a hidden pointer. If the GC runs
2836 * here, it will not recognize the hidden pointer as a
2837 * reference, and if the object behind it is not referenced
2838 * elsewhere, it will be freed. Once the world is restarted
2839 * we reveal the pointer, giving us a pointer to a freed
2840 * object. To make sure we don't return it, we load the
2841 * hidden pointer again. If it's still the same, we can be
2842 * sure the object reference is valid.
2845 obj = (GCObject*) REVEAL_POINTER (ptr);
2849 mono_memory_barrier ();
2852 * During the second bridge processing step the world is
2853 * running again. That step processes all weak links once
2854 * more to null those that refer to dead objects. Before that
2855 * is completed, those links must not be followed, so we
2856 * conservatively wait for bridge processing when any weak
2857 * link is dereferenced.
2859 sgen_client_bridge_wait_for_processing ();
2861 if ((void*)*link_addr_volatile != ptr)
2868 sgen_set_allow_synchronous_major (gboolean flag)
2870 if (!major_collector.is_concurrent)
2873 allow_synchronous_major = flag;
2878 sgen_env_var_error (const char *env_var, const char *fallback, const char *description_format, ...)
2882 va_start (ap, description_format);
2884 fprintf (stderr, "Warning: In environment variable `%s': ", env_var);
2885 vfprintf (stderr, description_format, ap);
2887 fprintf (stderr, " - %s", fallback);
2888 fprintf (stderr, "\n");
2894 parse_double_in_interval (const char *env_var, const char *opt_name, const char *opt, double min, double max, double *result)
2897 double val = strtod (opt, &endptr);
2898 if (endptr == opt) {
2899 sgen_env_var_error (env_var, "Using default value.", "`%s` must be a number.", opt_name);
2902 else if (val < min || val > max) {
2903 sgen_env_var_error (env_var, "Using default value.", "`%s` must be between %.2f - %.2f.", opt_name, min, max);
2915 char *major_collector_opt = NULL;
2916 char *minor_collector_opt = NULL;
2917 size_t max_heap = 0;
2918 size_t soft_limit = 0;
2920 gboolean debug_print_allowance = FALSE;
2921 double allowance_ratio = 0, save_target = 0;
2922 gboolean cement_enabled = TRUE;
2925 result = InterlockedCompareExchange (&gc_initialized, -1, 0);
2928 /* already inited */
2931 /* being inited by another thread */
2935 /* we will init it */
2938 g_assert_not_reached ();
2940 } while (result != 0);
2942 SGEN_TV_GETTIME (sgen_init_timestamp);
2944 #ifdef SGEN_WITHOUT_MONO
2945 mono_thread_smr_init ();
2948 LOCK_INIT (gc_mutex);
2950 gc_debug_file = stderr;
2952 LOCK_INIT (sgen_interruption_mutex);
2954 if ((env = g_getenv (MONO_GC_PARAMS_NAME))) {
2955 opts = g_strsplit (env, ",", -1);
2956 for (ptr = opts; *ptr; ++ptr) {
2958 if (g_str_has_prefix (opt, "major=")) {
2959 opt = strchr (opt, '=') + 1;
2960 major_collector_opt = g_strdup (opt);
2961 } else if (g_str_has_prefix (opt, "minor=")) {
2962 opt = strchr (opt, '=') + 1;
2963 minor_collector_opt = g_strdup (opt);
2971 sgen_init_internal_allocator ();
2972 sgen_init_nursery_allocator ();
2973 sgen_init_fin_weak_hash ();
2974 sgen_init_hash_table ();
2975 sgen_init_descriptors ();
2976 sgen_init_gray_queues ();
2977 sgen_init_allocator ();
2979 sgen_register_fixed_internal_mem_type (INTERNAL_MEM_SECTION, SGEN_SIZEOF_GC_MEM_SECTION);
2980 sgen_register_fixed_internal_mem_type (INTERNAL_MEM_GRAY_QUEUE, sizeof (GrayQueueSection));
2982 sgen_client_init ();
2984 if (!minor_collector_opt) {
2985 sgen_simple_nursery_init (&sgen_minor_collector);
2987 if (!strcmp (minor_collector_opt, "simple")) {
2989 sgen_simple_nursery_init (&sgen_minor_collector);
2990 } else if (!strcmp (minor_collector_opt, "split")) {
2991 sgen_split_nursery_init (&sgen_minor_collector);
2993 sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using `simple` instead.", "Unknown minor collector `%s'.", minor_collector_opt);
2994 goto use_simple_nursery;
2998 if (!major_collector_opt || !strcmp (major_collector_opt, "marksweep")) {
2999 use_marksweep_major:
3000 sgen_marksweep_init (&major_collector);
3001 } else if (!major_collector_opt || !strcmp (major_collector_opt, "marksweep-conc")) {
3002 sgen_marksweep_conc_init (&major_collector);
3004 sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using `marksweep` instead.", "Unknown major collector `%s'.", major_collector_opt);
3005 goto use_marksweep_major;
3008 sgen_nursery_size = DEFAULT_NURSERY_SIZE;
3010 if (major_collector.is_concurrent)
3011 cement_enabled = FALSE;
3014 gboolean usage_printed = FALSE;
3016 for (ptr = opts; *ptr; ++ptr) {
3018 if (!strcmp (opt, ""))
3020 if (g_str_has_prefix (opt, "major="))
3022 if (g_str_has_prefix (opt, "minor="))
3024 if (g_str_has_prefix (opt, "max-heap-size=")) {
3025 size_t page_size = mono_pagesize ();
3026 size_t max_heap_candidate = 0;
3027 opt = strchr (opt, '=') + 1;
3028 if (*opt && mono_gc_parse_environment_string_extract_number (opt, &max_heap_candidate)) {
3029 max_heap = (max_heap_candidate + page_size - 1) & ~(size_t)(page_size - 1);
3030 if (max_heap != max_heap_candidate)
3031 sgen_env_var_error (MONO_GC_PARAMS_NAME, "Rounding up.", "`max-heap-size` size must be a multiple of %d.", page_size);
3033 sgen_env_var_error (MONO_GC_PARAMS_NAME, NULL, "`max-heap-size` must be an integer.");
3037 if (g_str_has_prefix (opt, "soft-heap-limit=")) {
3038 opt = strchr (opt, '=') + 1;
3039 if (*opt && mono_gc_parse_environment_string_extract_number (opt, &soft_limit)) {
3040 if (soft_limit <= 0) {
3041 sgen_env_var_error (MONO_GC_PARAMS_NAME, NULL, "`soft-heap-limit` must be positive.");
3045 sgen_env_var_error (MONO_GC_PARAMS_NAME, NULL, "`soft-heap-limit` must be an integer.");
3051 if (g_str_has_prefix (opt, "nursery-size=")) {
3053 opt = strchr (opt, '=') + 1;
3054 if (*opt && mono_gc_parse_environment_string_extract_number (opt, &val)) {
3055 if ((val & (val - 1))) {
3056 sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using default value.", "`nursery-size` must be a power of two.");
3060 if (val < SGEN_MAX_NURSERY_WASTE) {
3061 sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using default value.",
3062 "`nursery-size` must be at least %d bytes.", SGEN_MAX_NURSERY_WASTE);
3066 sgen_nursery_size = val;
3067 sgen_nursery_bits = 0;
3068 while (ONE_P << (++ sgen_nursery_bits) != sgen_nursery_size)
3071 sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using default value.", "`nursery-size` must be an integer.");
3077 if (g_str_has_prefix (opt, "save-target-ratio=")) {
3079 opt = strchr (opt, '=') + 1;
3080 if (parse_double_in_interval (MONO_GC_PARAMS_NAME, "save-target-ratio", opt,
3081 SGEN_MIN_SAVE_TARGET_RATIO, SGEN_MAX_SAVE_TARGET_RATIO, &val)) {
3086 if (g_str_has_prefix (opt, "default-allowance-ratio=")) {
3088 opt = strchr (opt, '=') + 1;
3089 if (parse_double_in_interval (MONO_GC_PARAMS_NAME, "default-allowance-ratio", opt,
3090 SGEN_MIN_ALLOWANCE_NURSERY_SIZE_RATIO, SGEN_MIN_ALLOWANCE_NURSERY_SIZE_RATIO, &val)) {
3091 allowance_ratio = val;
3095 if (g_str_has_prefix (opt, "allow-synchronous-major=")) {
3096 if (!major_collector.is_concurrent) {
3097 sgen_env_var_error (MONO_GC_PARAMS_NAME, "Ignoring.", "`allow-synchronous-major` is only valid for the concurrent major collector.");
3101 opt = strchr (opt, '=') + 1;
3103 if (!strcmp (opt, "yes")) {
3104 allow_synchronous_major = TRUE;
3105 } else if (!strcmp (opt, "no")) {
3106 allow_synchronous_major = FALSE;
3108 sgen_env_var_error (MONO_GC_PARAMS_NAME, "Using default value.", "`allow-synchronous-major` must be either `yes' or `no'.");
3113 if (!strcmp (opt, "cementing")) {
3114 cement_enabled = TRUE;
3117 if (!strcmp (opt, "no-cementing")) {
3118 cement_enabled = FALSE;
3122 if (major_collector.handle_gc_param && major_collector.handle_gc_param (opt))
3125 if (sgen_minor_collector.handle_gc_param && sgen_minor_collector.handle_gc_param (opt))
3128 if (sgen_client_handle_gc_param (opt))
3131 sgen_env_var_error (MONO_GC_PARAMS_NAME, "Ignoring.", "Unknown option `%s`.", opt);
3136 fprintf (stderr, "\n%s must be a comma-delimited list of one or more of the following:\n", MONO_GC_PARAMS_NAME);
3137 fprintf (stderr, " max-heap-size=N (where N is an integer, possibly with a k, m or a g suffix)\n");
3138 fprintf (stderr, " soft-heap-limit=n (where N is an integer, possibly with a k, m or a g suffix)\n");
3139 fprintf (stderr, " nursery-size=N (where N is an integer, possibly with a k, m or a g suffix)\n");
3140 fprintf (stderr, " major=COLLECTOR (where COLLECTOR is `marksweep', `marksweep-conc', `marksweep-par')\n");
3141 fprintf (stderr, " minor=COLLECTOR (where COLLECTOR is `simple' or `split')\n");
3142 fprintf (stderr, " wbarrier=WBARRIER (where WBARRIER is `remset' or `cardtable')\n");
3143 fprintf (stderr, " [no-]cementing\n");
3144 if (major_collector.is_concurrent)
3145 fprintf (stderr, " allow-synchronous-major=FLAG (where FLAG is `yes' or `no')\n");
3146 if (major_collector.print_gc_param_usage)
3147 major_collector.print_gc_param_usage ();
3148 if (sgen_minor_collector.print_gc_param_usage)
3149 sgen_minor_collector.print_gc_param_usage ();
3150 sgen_client_print_gc_params_usage ();
3151 fprintf (stderr, " Experimental options:\n");
3152 fprintf (stderr, " save-target-ratio=R (where R must be between %.2f - %.2f).\n", SGEN_MIN_SAVE_TARGET_RATIO, SGEN_MAX_SAVE_TARGET_RATIO);
3153 fprintf (stderr, " default-allowance-ratio=R (where R must be between %.2f - %.2f).\n", SGEN_MIN_ALLOWANCE_NURSERY_SIZE_RATIO, SGEN_MAX_ALLOWANCE_NURSERY_SIZE_RATIO);
3154 fprintf (stderr, "\n");
3156 usage_printed = TRUE;
3161 if (major_collector_opt)
3162 g_free (major_collector_opt);
3164 if (minor_collector_opt)
3165 g_free (minor_collector_opt);
3169 if (major_collector.is_concurrent && cement_enabled) {
3170 sgen_env_var_error (MONO_GC_PARAMS_NAME, "Ignoring.", "`cementing` is not supported on concurrent major collectors.");
3171 cement_enabled = FALSE;
3174 sgen_cement_init (cement_enabled);
3176 if ((env = g_getenv (MONO_GC_DEBUG_NAME))) {
3177 gboolean usage_printed = FALSE;
3179 opts = g_strsplit (env, ",", -1);
3180 for (ptr = opts; ptr && *ptr; ptr ++) {
3182 if (!strcmp (opt, ""))
3184 if (opt [0] >= '0' && opt [0] <= '9') {
3185 gc_debug_level = atoi (opt);
3190 char *rf = g_strdup_printf ("%s.%d", opt, mono_process_current_pid ());
3191 gc_debug_file = fopen (rf, "wb");
3193 gc_debug_file = stderr;
3196 } else if (!strcmp (opt, "print-allowance")) {
3197 debug_print_allowance = TRUE;
3198 } else if (!strcmp (opt, "print-pinning")) {
3199 sgen_pin_stats_enable ();
3200 } else if (!strcmp (opt, "verify-before-allocs")) {
3201 verify_before_allocs = 1;
3202 has_per_allocation_action = TRUE;
3203 } else if (g_str_has_prefix (opt, "verify-before-allocs=")) {
3204 char *arg = strchr (opt, '=') + 1;
3205 verify_before_allocs = atoi (arg);
3206 has_per_allocation_action = TRUE;
3207 } else if (!strcmp (opt, "collect-before-allocs")) {
3208 collect_before_allocs = 1;
3209 has_per_allocation_action = TRUE;
3210 } else if (g_str_has_prefix (opt, "collect-before-allocs=")) {
3211 char *arg = strchr (opt, '=') + 1;
3212 has_per_allocation_action = TRUE;
3213 collect_before_allocs = atoi (arg);
3214 } else if (!strcmp (opt, "verify-before-collections")) {
3215 whole_heap_check_before_collection = TRUE;
3216 } else if (!strcmp (opt, "check-at-minor-collections")) {
3217 consistency_check_at_minor_collection = TRUE;
3218 nursery_clear_policy = CLEAR_AT_GC;
3219 } else if (!strcmp (opt, "mod-union-consistency-check")) {
3220 if (!major_collector.is_concurrent) {
3221 sgen_env_var_error (MONO_GC_DEBUG_NAME, "Ignoring.", "`mod-union-consistency-check` only works with concurrent major collector.");
3224 mod_union_consistency_check = TRUE;
3225 } else if (!strcmp (opt, "check-mark-bits")) {
3226 check_mark_bits_after_major_collection = TRUE;
3227 } else if (!strcmp (opt, "check-nursery-pinned")) {
3228 check_nursery_objects_pinned = TRUE;
3229 } else if (!strcmp (opt, "clear-at-gc")) {
3230 nursery_clear_policy = CLEAR_AT_GC;
3231 } else if (!strcmp (opt, "clear-nursery-at-gc")) {
3232 nursery_clear_policy = CLEAR_AT_GC;
3233 } else if (!strcmp (opt, "clear-at-tlab-creation")) {
3234 nursery_clear_policy = CLEAR_AT_TLAB_CREATION;
3235 } else if (!strcmp (opt, "debug-clear-at-tlab-creation")) {
3236 nursery_clear_policy = CLEAR_AT_TLAB_CREATION_DEBUG;
3237 } else if (!strcmp (opt, "check-scan-starts")) {
3238 do_scan_starts_check = TRUE;
3239 } else if (!strcmp (opt, "verify-nursery-at-minor-gc")) {
3240 do_verify_nursery = TRUE;
3241 } else if (!strcmp (opt, "check-concurrent")) {
3242 if (!major_collector.is_concurrent) {
3243 sgen_env_var_error (MONO_GC_DEBUG_NAME, "Ignoring.", "`check-concurrent` only works with concurrent major collectors.");
3246 do_concurrent_checks = TRUE;
3247 } else if (!strcmp (opt, "dump-nursery-at-minor-gc")) {
3248 do_dump_nursery_content = TRUE;
3249 } else if (!strcmp (opt, "disable-minor")) {
3250 disable_minor_collections = TRUE;
3251 } else if (!strcmp (opt, "disable-major")) {
3252 disable_major_collections = TRUE;
3253 } else if (g_str_has_prefix (opt, "heap-dump=")) {
3254 char *filename = strchr (opt, '=') + 1;
3255 nursery_clear_policy = CLEAR_AT_GC;
3256 sgen_debug_enable_heap_dump (filename);
3257 } else if (g_str_has_prefix (opt, "binary-protocol=")) {
3258 char *filename = strchr (opt, '=') + 1;
3259 char *colon = strrchr (filename, ':');
3262 if (!mono_gc_parse_environment_string_extract_number (colon + 1, &limit)) {
3263 sgen_env_var_error (MONO_GC_DEBUG_NAME, "Ignoring limit.", "Binary protocol file size limit must be an integer.");
3268 binary_protocol_init (filename, (long long)limit);
3269 } else if (!strcmp (opt, "nursery-canaries")) {
3270 do_verify_nursery = TRUE;
3271 enable_nursery_canaries = TRUE;
3272 } else if (!sgen_client_handle_gc_debug (opt)) {
3273 sgen_env_var_error (MONO_GC_DEBUG_NAME, "Ignoring.", "Unknown option `%s`.", opt);
3278 fprintf (stderr, "\n%s must be of the format [<l>[:<filename>]|<option>]+ where <l> is a debug level 0-9.\n", MONO_GC_DEBUG_NAME);
3279 fprintf (stderr, "Valid <option>s are:\n");
3280 fprintf (stderr, " collect-before-allocs[=<n>]\n");
3281 fprintf (stderr, " verify-before-allocs[=<n>]\n");
3282 fprintf (stderr, " check-at-minor-collections\n");
3283 fprintf (stderr, " check-mark-bits\n");
3284 fprintf (stderr, " check-nursery-pinned\n");
3285 fprintf (stderr, " verify-before-collections\n");
3286 fprintf (stderr, " verify-nursery-at-minor-gc\n");
3287 fprintf (stderr, " dump-nursery-at-minor-gc\n");
3288 fprintf (stderr, " disable-minor\n");
3289 fprintf (stderr, " disable-major\n");
3290 fprintf (stderr, " check-concurrent\n");
3291 fprintf (stderr, " clear-[nursery-]at-gc\n");
3292 fprintf (stderr, " clear-at-tlab-creation\n");
3293 fprintf (stderr, " debug-clear-at-tlab-creation\n");
3294 fprintf (stderr, " check-scan-starts\n");
3295 fprintf (stderr, " print-allowance\n");
3296 fprintf (stderr, " print-pinning\n");
3297 fprintf (stderr, " heap-dump=<filename>\n");
3298 fprintf (stderr, " binary-protocol=<filename>[:<file-size-limit>]\n");
3299 fprintf (stderr, " nursery-canaries\n");
3300 sgen_client_print_gc_debug_usage ();
3301 fprintf (stderr, "\n");
3303 usage_printed = TRUE;
3309 if (check_mark_bits_after_major_collection)
3310 nursery_clear_policy = CLEAR_AT_GC;
3312 if (major_collector.post_param_init)
3313 major_collector.post_param_init (&major_collector);
3315 if (major_collector.needs_thread_pool)
3316 sgen_workers_init (1);
3318 sgen_memgov_init (max_heap, soft_limit, debug_print_allowance, allowance_ratio, save_target);
3320 memset (&remset, 0, sizeof (remset));
3322 sgen_card_table_init (&remset);
3328 sgen_get_nursery_clear_policy (void)
3330 return nursery_clear_policy;
3340 sgen_gc_unlock (void)
3342 gboolean try_free = sgen_try_free_some_memory;
3343 sgen_try_free_some_memory = FALSE;
3344 mono_mutex_unlock (&gc_mutex);
3346 mono_thread_hazardous_try_free_some ();
3350 sgen_major_collector_iterate_live_block_ranges (sgen_cardtable_block_callback callback)
3352 major_collector.iterate_live_block_ranges (callback);
3356 sgen_get_major_collector (void)
3358 return &major_collector;
3362 sgen_get_remset (void)
3368 count_cards (long long *major_total, long long *major_marked, long long *los_total, long long *los_marked)
3370 sgen_get_major_collector ()->count_cards (major_total, major_marked);
3371 sgen_los_count_cards (los_total, los_marked);
3374 static gboolean world_is_stopped = FALSE;
3376 /* LOCKING: assumes the GC lock is held */
3378 sgen_stop_world (int generation)
3380 long long major_total = -1, major_marked = -1, los_total = -1, los_marked = -1;
3382 SGEN_ASSERT (0, !world_is_stopped, "Why are we stopping a stopped world?");
3384 binary_protocol_world_stopping (generation, sgen_timestamp (), (gpointer)mono_native_thread_id_get ());
3386 sgen_client_stop_world (generation);
3388 world_is_stopped = TRUE;
3390 if (binary_protocol_is_heavy_enabled ())
3391 count_cards (&major_total, &major_marked, &los_total, &los_marked);
3392 binary_protocol_world_stopped (generation, sgen_timestamp (), major_total, major_marked, los_total, los_marked);
3395 /* LOCKING: assumes the GC lock is held */
3397 sgen_restart_world (int generation, GGTimingInfo *timing)
3399 long long major_total = -1, major_marked = -1, los_total = -1, los_marked = -1;
3401 SGEN_ASSERT (0, world_is_stopped, "Why are we restarting a running world?");
3403 if (binary_protocol_is_heavy_enabled ())
3404 count_cards (&major_total, &major_marked, &los_total, &los_marked);
3405 binary_protocol_world_restarting (generation, sgen_timestamp (), major_total, major_marked, los_total, los_marked);
3407 sgen_client_restart_world (generation, timing);
3409 world_is_stopped = FALSE;
3411 binary_protocol_world_restarted (generation, sgen_timestamp ());
3413 sgen_try_free_some_memory = TRUE;
3415 if (sgen_client_bridge_need_processing ())
3416 sgen_client_bridge_processing_finish (generation);
3418 sgen_memgov_collection_end (generation, timing, timing ? 2 : 0);
3422 sgen_is_world_stopped (void)
3424 return world_is_stopped;
3428 sgen_check_whole_heap_stw (void)
3430 sgen_stop_world (0);
3431 sgen_clear_nursery_fragments ();
3432 sgen_check_whole_heap (FALSE);
3433 sgen_restart_world (0, NULL);
3437 sgen_timestamp (void)
3439 SGEN_TV_DECLARE (timestamp);
3440 SGEN_TV_GETTIME (timestamp);
3441 return SGEN_TV_ELAPSED (sgen_init_timestamp, timestamp);
3444 #endif /* HAVE_SGEN_GC */