5 * Copyright 2001-2003 Ximian, Inc
6 * Copyright 2003-2010 Novell, Inc.
7 * Copyright (C) 2012 Xamarin Inc
9 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
17 #include "mono/sgen/sgen-gc.h"
18 #include "mono/sgen/sgen-pinning.h"
19 #include "mono/sgen/sgen-protocol.h"
20 #include "mono/sgen/sgen-pointer-queue.h"
21 #include "mono/sgen/sgen-client.h"
23 static SgenPointerQueue pin_queue;
24 static size_t last_num_pinned = 0;
26 * While we hold the pin_queue_mutex, all objects in pin_queue_objs will
27 * stay pinned, which means they can't move, therefore they can be scanned.
29 static SgenPointerQueue pin_queue_objs;
30 static mono_mutex_t pin_queue_mutex;
32 #define PIN_HASH_SIZE 1024
33 static void *pin_hash_filter [PIN_HASH_SIZE];
36 sgen_pinning_init (void)
38 mono_os_mutex_init (&pin_queue_mutex);
42 sgen_init_pinning (void)
44 mono_os_mutex_lock (&pin_queue_mutex);
45 memset (pin_hash_filter, 0, sizeof (pin_hash_filter));
46 pin_queue.mem_type = INTERNAL_MEM_PIN_QUEUE;
47 sgen_pointer_queue_clear (&pin_queue_objs);
51 sgen_finish_pinning (void)
53 last_num_pinned = pin_queue.next_slot;
54 sgen_pointer_queue_clear (&pin_queue);
55 mono_os_mutex_unlock (&pin_queue_mutex);
59 sgen_pinning_register_pinned_in_nursery (GCObject *obj)
61 sgen_pointer_queue_add (&pin_queue_objs, obj);
65 sgen_scan_pin_queue_objects (ScanCopyContext ctx)
68 ScanObjectFunc scan_func = ctx.ops->scan_object;
70 mono_os_mutex_lock (&pin_queue_mutex);
71 for (i = 0; i < pin_queue_objs.next_slot; ++i) {
72 GCObject *obj = (GCObject *)pin_queue_objs.data [i];
73 scan_func (obj, sgen_obj_get_descriptor_safe (obj), ctx.queue);
75 mono_os_mutex_unlock (&pin_queue_mutex);
79 sgen_pin_stage_ptr (void *ptr)
81 /*very simple multiplicative hash function, tons better than simple and'ng */
82 int hash_idx = ((mword)ptr * 1737350767) & (PIN_HASH_SIZE - 1);
83 if (pin_hash_filter [hash_idx] == ptr)
86 pin_hash_filter [hash_idx] = ptr;
88 sgen_pointer_queue_add (&pin_queue, ptr);
92 sgen_find_optimized_pin_queue_area (void *start, void *end, size_t *first_out, size_t *last_out)
94 size_t first = sgen_pointer_queue_search (&pin_queue, start);
95 size_t last = sgen_pointer_queue_search (&pin_queue, end);
96 SGEN_ASSERT (0, last == pin_queue.next_slot || pin_queue.data [last] >= end, "Pin queue search gone awry");
103 sgen_pinning_get_entry (size_t index)
105 SGEN_ASSERT (0, index <= pin_queue.next_slot, "Pin queue entry out of range");
106 return &pin_queue.data [index];
110 sgen_find_section_pin_queue_start_end (GCMemSection *section)
112 SGEN_LOG (6, "Pinning from section %p (%p-%p)", section, section->data, section->end_data);
114 sgen_find_optimized_pin_queue_area (section->data, section->end_data,
115 §ion->pin_queue_first_entry, §ion->pin_queue_last_entry);
117 SGEN_LOG (6, "Found %zd pinning addresses in section %p",
118 section->pin_queue_last_entry - section->pin_queue_first_entry, section);
121 /*This will setup the given section for the while pin queue. */
123 sgen_pinning_setup_section (GCMemSection *section)
125 section->pin_queue_first_entry = 0;
126 section->pin_queue_last_entry = pin_queue.next_slot;
130 sgen_pinning_trim_queue_to_section (GCMemSection *section)
132 SGEN_ASSERT (0, section->pin_queue_first_entry == 0, "Pin queue trimming assumes the whole pin queue is used by the nursery");
133 pin_queue.next_slot = section->pin_queue_last_entry;
137 * This is called when we've run out of memory during a major collection.
139 * After collecting potential pin entries and sorting the array, this is what it looks like:
141 * +--------------------+---------------------------------------------+--------------------+
142 * | major heap entries | nursery entries | major heap entries |
143 * +--------------------+---------------------------------------------+--------------------+
145 * Of course there might not be major heap entries before and/or after the nursery entries,
146 * depending on where the major heap sections are in the address space, and whether there
147 * were any potential pointers there.
149 * When we pin nursery objects, we compact the nursery part of the pin array, which leaves
150 * discarded entries after the ones that actually pointed to nursery objects:
152 * +--------------------+-----------------+---------------------------+--------------------+
153 * | major heap entries | nursery entries | discarded nursery entries | major heap entries |
154 * +--------------------+-----------------+---------------------------+--------------------+
156 * When, due to being out of memory, we late pin more objects, the pin array looks like
159 * +--------------------+-----------------+---------------------------+--------------------+--------------+
160 * | major heap entries | nursery entries | discarded nursery entries | major heap entries | late entries |
161 * +--------------------+-----------------+---------------------------+--------------------+--------------+
163 * This function gets rid of the discarded nursery entries by nulling them out. Note that
164 * we can late pin objects not only in the nursery but also in the major heap, which happens
165 * when evacuation fails.
168 sgen_pin_queue_clear_discarded_entries (GCMemSection *section, size_t max_pin_slot)
170 void **start = sgen_pinning_get_entry (section->pin_queue_last_entry);
171 void **end = sgen_pinning_get_entry (max_pin_slot);
174 for (; start < end; ++start) {
176 if ((char*)addr < section->data || (char*)addr > section->end_data)
182 /* reduce the info in the pin queue, removing duplicate pointers and sorting them */
184 sgen_optimize_pin_queue (void)
186 sgen_pointer_queue_sort_uniq (&pin_queue);
190 sgen_get_pinned_count (void)
192 return pin_queue.next_slot;
196 sgen_dump_pin_queue (void)
200 for (i = 0; i < last_num_pinned; ++i) {
201 GCObject *ptr = (GCObject *)pin_queue.data [i];
202 SGEN_LOG (3, "Bastard pinning obj %p (%s), size: %zd", ptr, sgen_client_vtable_get_name (SGEN_LOAD_VTABLE (ptr)), sgen_safe_object_get_size (ptr));
206 typedef struct _CementHashEntry CementHashEntry;
207 struct _CementHashEntry {
210 gboolean forced; /* if it should stay cemented after the finishing pause */
213 static CementHashEntry cement_hash [SGEN_CEMENT_HASH_SIZE];
215 static gboolean cement_enabled = TRUE;
218 sgen_cement_init (gboolean enabled)
220 cement_enabled = enabled;
224 sgen_cement_reset (void)
227 for (i = 0; i < SGEN_CEMENT_HASH_SIZE; i++) {
228 if (cement_hash [i].forced) {
229 cement_hash [i].forced = FALSE;
231 cement_hash [i].obj = NULL;
232 cement_hash [i].count = 0;
235 binary_protocol_cement_reset ();
240 * The pin_queue should be full and sorted, without entries from the cemented
241 * objects. We traverse the cement hash and check if each object is pinned in
242 * the pin_queue (the pin_queue contains entries between obj and obj+obj_len)
245 sgen_cement_force_pinned (void)
252 for (i = 0; i < SGEN_CEMENT_HASH_SIZE; i++) {
253 GCObject *obj = cement_hash [i].obj;
257 if (cement_hash [i].count < SGEN_CEMENT_THRESHOLD)
259 SGEN_ASSERT (0, !cement_hash [i].forced, "Why do we have a forced cemented object before forcing ?");
261 /* Returns the index of the target or of the first element greater than it */
262 index = sgen_pointer_queue_search (&pin_queue, obj);
263 if (index == pin_queue.next_slot)
265 SGEN_ASSERT (0, pin_queue.data [index] >= (gpointer)obj, "Binary search should return a pointer greater than the search target");
266 if (pin_queue.data [index] < (gpointer)((char*)obj + sgen_safe_object_get_size (obj)))
267 cement_hash [i].forced = TRUE;
272 sgen_cement_is_forced (GCObject *obj)
274 guint hv = sgen_aligned_addr_hash (obj);
275 int i = SGEN_CEMENT_HASH (hv);
277 SGEN_ASSERT (5, sgen_ptr_in_nursery (obj), "Looking up cementing for non-nursery objects makes no sense");
282 if (!cement_hash [i].obj)
284 if (cement_hash [i].obj != obj)
287 return cement_hash [i].forced;
291 sgen_cement_lookup (GCObject *obj)
293 guint hv = sgen_aligned_addr_hash (obj);
294 int i = SGEN_CEMENT_HASH (hv);
296 SGEN_ASSERT (5, sgen_ptr_in_nursery (obj), "Looking up cementing for non-nursery objects makes no sense");
301 if (!cement_hash [i].obj)
303 if (cement_hash [i].obj != obj)
306 return cement_hash [i].count >= SGEN_CEMENT_THRESHOLD;
310 sgen_cement_lookup_or_register (GCObject *obj)
314 CementHashEntry *hash = cement_hash;
319 hv = sgen_aligned_addr_hash (obj);
320 i = SGEN_CEMENT_HASH (hv);
322 SGEN_ASSERT (5, sgen_ptr_in_nursery (obj), "Can only cement pointers to nursery objects");
326 old_obj = InterlockedCompareExchangePointer ((gpointer*)&hash [i].obj, obj, NULL);
327 /* Check if the slot was occupied by some other object */
328 if (old_obj != NULL && old_obj != obj)
330 } else if (hash [i].obj != obj) {
334 if (hash [i].count >= SGEN_CEMENT_THRESHOLD)
337 if (InterlockedIncrement ((gint32*)&hash [i].count) == SGEN_CEMENT_THRESHOLD) {
338 SGEN_ASSERT (9, sgen_get_current_collection_generation () >= 0, "We can only cement objects when we're in a collection pause.");
339 SGEN_ASSERT (9, SGEN_OBJECT_IS_PINNED (obj), "Can only cement pinned objects");
340 SGEN_CEMENT_OBJECT (obj);
342 binary_protocol_cement (obj, (gpointer)SGEN_LOAD_VTABLE (obj),
343 (int)sgen_safe_object_get_size (obj));
350 pin_from_hash (CementHashEntry *hash, gboolean has_been_reset)
353 for (i = 0; i < SGEN_CEMENT_HASH_SIZE; ++i) {
358 SGEN_ASSERT (5, hash [i].count >= SGEN_CEMENT_THRESHOLD, "Cementing hash inconsistent");
360 sgen_pin_stage_ptr (hash [i].obj);
361 binary_protocol_cement_stage (hash [i].obj);
362 /* FIXME: do pin stats if enabled */
364 SGEN_CEMENT_OBJECT (hash [i].obj);
369 sgen_pin_cemented_objects (void)
371 pin_from_hash (cement_hash, TRUE);
375 sgen_cement_clear_below_threshold (void)
378 for (i = 0; i < SGEN_CEMENT_HASH_SIZE; ++i) {
379 if (cement_hash [i].count < SGEN_CEMENT_THRESHOLD) {
380 cement_hash [i].obj = NULL;
381 cement_hash [i].count = 0;
386 #endif /* HAVE_SGEN_GC */