3 * Card table implementation for sgen
6 * Rodrigo Kumpera (rkumpera@novell.com)
8 * Copyright 2001-2003 Ximian, Inc
9 * Copyright 2003-2010 Novell, Inc.
10 * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
11 * Copyright (C) 2012 Xamarin Inc
13 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
21 #include "mono/sgen/sgen-gc.h"
22 #include "mono/sgen/sgen-cardtable.h"
23 #include "mono/sgen/sgen-memory-governor.h"
24 #include "mono/sgen/sgen-protocol.h"
25 #include "mono/sgen/sgen-layout-stats.h"
26 #include "mono/sgen/sgen-client.h"
27 #include "mono/sgen/gc-internal-agnostic.h"
28 #include "mono/utils/mono-memory-model.h"
30 //#define CARDTABLE_STATS
35 #ifdef HAVE_SYS_MMAN_H
38 #include <sys/types.h>
40 guint8 *sgen_cardtable;
42 static gboolean need_mod_union;
44 #ifdef HEAVY_STATISTICS
46 guint64 scanned_cards;
47 guint64 scanned_objects;
48 guint64 remarked_cards;
49 static guint64 large_objects;
50 static guint64 bloby_objects;
52 static guint64 major_card_scan_time;
53 static guint64 los_card_scan_time;
55 static guint64 last_major_scan_time;
56 static guint64 last_los_scan_time;
59 sgen_card_table_number_of_cards_in_range (mword address, mword size)
61 mword end = address + MAX (1, size) - 1;
62 return (end >> CARD_BITS) - (address >> CARD_BITS) + 1;
66 sgen_card_table_wbarrier_set_field (GCObject *obj, gpointer field_ptr, GCObject* value)
68 *(void**)field_ptr = value;
69 if (need_mod_union || sgen_ptr_in_nursery (value))
70 sgen_card_table_mark_address ((mword)field_ptr);
71 sgen_dummy_use (value);
75 sgen_card_table_wbarrier_arrayref_copy (gpointer dest_ptr, gpointer src_ptr, int count)
77 gpointer *dest = (gpointer *)dest_ptr;
78 gpointer *src = (gpointer *)src_ptr;
80 /*overlapping that required backward copying*/
81 if (src < dest && (src + count) > dest) {
82 gpointer *start = dest;
86 for (; dest >= start; --src, --dest) {
87 gpointer value = *src;
88 SGEN_UPDATE_REFERENCE_ALLOW_NULL (dest, value);
89 if (need_mod_union || sgen_ptr_in_nursery (value))
90 sgen_card_table_mark_address ((mword)dest);
91 sgen_dummy_use (value);
94 gpointer *end = dest + count;
95 for (; dest < end; ++src, ++dest) {
96 gpointer value = *src;
97 SGEN_UPDATE_REFERENCE_ALLOW_NULL (dest, value);
98 if (need_mod_union || sgen_ptr_in_nursery (value))
99 sgen_card_table_mark_address ((mword)dest);
100 sgen_dummy_use (value);
106 sgen_card_table_wbarrier_value_copy (gpointer dest, gpointer src, int count, size_t element_size)
108 size_t size = count * element_size;
111 ENTER_CRITICAL_REGION;
113 mono_gc_memmove_atomic (dest, src, size);
114 sgen_card_table_mark_range ((mword)dest, size);
116 EXIT_CRITICAL_REGION;
120 sgen_card_table_wbarrier_object_copy (GCObject* obj, GCObject *src)
122 size_t size = sgen_client_par_object_get_size (SGEN_LOAD_VTABLE_UNCHECKED (obj), obj);
125 ENTER_CRITICAL_REGION;
127 mono_gc_memmove_aligned ((char*)obj + SGEN_CLIENT_OBJECT_HEADER_SIZE, (char*)src + SGEN_CLIENT_OBJECT_HEADER_SIZE,
128 size - SGEN_CLIENT_OBJECT_HEADER_SIZE);
129 sgen_card_table_mark_range ((mword)obj, size);
131 EXIT_CRITICAL_REGION;
135 sgen_card_table_wbarrier_generic_nostore (gpointer ptr)
137 sgen_card_table_mark_address ((mword)ptr);
140 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
142 guint8 *sgen_shadow_cardtable;
144 #define SGEN_CARDTABLE_END (sgen_cardtable + CARD_COUNT_IN_BYTES)
147 sgen_card_table_region_begin_scanning (mword start, mword size)
149 mword end = start + size;
150 /*XXX this can be improved to work on words and have a single loop induction var */
151 while (start < end) {
152 if (sgen_card_table_card_begin_scanning (start))
154 start += CARD_SIZE_IN_BYTES;
162 sgen_card_table_region_begin_scanning (mword start, mword size)
164 gboolean res = FALSE;
165 guint8 *card = sgen_card_table_get_card_address (start);
166 guint8 *end = card + sgen_card_table_number_of_cards_in_range (start, size);
168 /*XXX this can be improved to work on words and have a branchless body */
169 while (card != end) {
176 memset (sgen_card_table_get_card_address (start), 0, size >> CARD_BITS);
183 /*FIXME this assumes that major blocks are multiple of 4K which is pretty reasonable */
185 sgen_card_table_get_card_data (guint8 *data_dest, mword address, mword cards)
187 mword *start = (mword*)sgen_card_table_get_card_scan_address (address);
188 mword *dest = (mword*)data_dest;
189 mword *end = (mword*)(data_dest + cards);
192 for (; dest < end; ++dest, ++start) {
197 #ifndef SGEN_HAVE_OVERLAPPING_CARDS
206 sgen_card_table_align_pointer (void *ptr)
208 return (void*)((mword)ptr & ~(CARD_SIZE_IN_BYTES - 1));
212 sgen_card_table_mark_range (mword address, mword size)
214 mword num_cards = sgen_card_table_number_of_cards_in_range (address, size);
215 guint8 *start = sgen_card_table_get_card_address (address);
217 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
219 * FIXME: There's a theoretical bug here, namely that the card table is allocated so
220 * far toward the end of the address space that start + num_cards overflows.
222 guint8 *end = start + num_cards;
223 SGEN_ASSERT (0, num_cards <= CARD_COUNT_IN_BYTES, "How did we get an object larger than the card table?");
224 if (end > SGEN_CARDTABLE_END) {
225 memset (start, 1, SGEN_CARDTABLE_END - start);
226 memset (sgen_cardtable, 1, end - SGEN_CARDTABLE_END);
231 memset (start, 1, num_cards);
235 sgen_card_table_is_range_marked (guint8 *cards, mword address, mword size)
237 guint8 *end = cards + sgen_card_table_number_of_cards_in_range (address, size);
239 /*This is safe since this function is only called by code that only passes continuous card blocks*/
240 while (cards != end) {
249 sgen_card_table_record_pointer (gpointer address)
251 *sgen_card_table_get_card_address ((mword)address) = 1;
255 sgen_card_table_find_address (char *addr)
257 return sgen_card_table_address_is_marked ((mword)addr);
261 sgen_card_table_find_address_with_cards (char *cards_start, guint8 *cards, char *addr)
263 cards_start = (char *)sgen_card_table_align_pointer (cards_start);
264 return cards [(addr - cards_start) >> CARD_BITS];
268 update_mod_union (guint8 *dest, guint8 *start_card, size_t num_cards)
271 /* Marking from another thread can happen while we mark here */
272 for (i = 0; i < num_cards; ++i) {
279 sgen_card_table_alloc_mod_union (char *obj, mword obj_size)
281 size_t num_cards = sgen_card_table_number_of_cards_in_range ((mword) obj, obj_size);
282 guint8 *mod_union = (guint8 *)sgen_alloc_internal_dynamic (num_cards, INTERNAL_MEM_CARDTABLE_MOD_UNION, TRUE);
283 memset (mod_union, 0, num_cards);
288 sgen_card_table_free_mod_union (guint8 *mod_union, char *obj, mword obj_size)
290 size_t num_cards = sgen_card_table_number_of_cards_in_range ((mword) obj, obj_size);
291 sgen_free_internal_dynamic (mod_union, num_cards, INTERNAL_MEM_CARDTABLE_MOD_UNION);
295 sgen_card_table_update_mod_union_from_cards (guint8 *dest, guint8 *start_card, size_t num_cards)
297 SGEN_ASSERT (0, dest, "Why don't we have a mod union?");
298 update_mod_union (dest, start_card, num_cards);
302 sgen_card_table_update_mod_union (guint8 *dest, char *obj, mword obj_size, size_t *out_num_cards)
304 guint8 *start_card = sgen_card_table_get_card_address ((mword)obj);
305 #ifndef SGEN_HAVE_OVERLAPPING_CARDS
306 guint8 *end_card = sgen_card_table_get_card_address ((mword)obj + obj_size - 1) + 1;
310 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
313 rest = num_cards = sgen_card_table_number_of_cards_in_range ((mword) obj, obj_size);
315 while (start_card + rest > SGEN_CARDTABLE_END) {
316 size_t count = SGEN_CARDTABLE_END - start_card;
317 sgen_card_table_update_mod_union_from_cards (dest, start_card, count);
320 start_card = sgen_cardtable;
324 num_cards = end_card - start_card;
327 sgen_card_table_update_mod_union_from_cards (dest, start_card, num_cards);
330 *out_num_cards = num_cards;
333 /* Preclean cards and saves the cards that need to be scanned afterwards in cards_preclean */
335 sgen_card_table_preclean_mod_union (guint8 *cards, guint8 *cards_preclean, size_t num_cards)
339 memcpy (cards_preclean, cards, num_cards);
340 for (i = 0; i < num_cards; i++) {
341 if (cards_preclean [i]) {
346 * When precleaning we need to make sure the card cleaning
347 * takes place before the object is scanned. If we don't
348 * do this we could finish scanning the object and, before
349 * the cleaning of the card takes place, another thread
350 * could dirty the object, mark the mod_union card only for
351 * us to clean it back, without scanning the object again.
353 mono_memory_barrier ();
356 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
359 move_cards_to_shadow_table (mword start, mword size)
361 guint8 *from = sgen_card_table_get_card_address (start);
362 guint8 *to = sgen_card_table_get_shadow_card_address (start);
363 size_t bytes = sgen_card_table_number_of_cards_in_range (start, size);
365 if (bytes >= CARD_COUNT_IN_BYTES) {
366 memcpy (sgen_shadow_cardtable, sgen_cardtable, CARD_COUNT_IN_BYTES);
367 } else if (to + bytes > SGEN_SHADOW_CARDTABLE_END) {
368 size_t first_chunk = SGEN_SHADOW_CARDTABLE_END - to;
369 size_t second_chunk = MIN (CARD_COUNT_IN_BYTES, bytes) - first_chunk;
371 memcpy (to, from, first_chunk);
372 memcpy (sgen_shadow_cardtable, sgen_cardtable, second_chunk);
374 memcpy (to, from, bytes);
379 clear_cards (mword start, mword size)
381 guint8 *addr = sgen_card_table_get_card_address (start);
382 size_t bytes = sgen_card_table_number_of_cards_in_range (start, size);
384 if (bytes >= CARD_COUNT_IN_BYTES) {
385 memset (sgen_cardtable, 0, CARD_COUNT_IN_BYTES);
386 } else if (addr + bytes > SGEN_CARDTABLE_END) {
387 size_t first_chunk = SGEN_CARDTABLE_END - addr;
389 memset (addr, 0, first_chunk);
390 memset (sgen_cardtable, 0, bytes - first_chunk);
392 memset (addr, 0, bytes);
400 clear_cards (mword start, mword size)
402 memset (sgen_card_table_get_card_address (start), 0, sgen_card_table_number_of_cards_in_range (start, size));
409 sgen_card_table_clear_cards (void)
411 /*XXX we could do this in 2 ways. using mincore or iterating over all sections/los objects */
412 sgen_major_collector_iterate_block_ranges (clear_cards);
413 sgen_los_iterate_live_block_ranges (clear_cards);
414 sgen_wbroots_iterate_live_block_ranges (clear_cards);
418 sgen_card_table_scan_remsets (ScanCopyContext ctx)
420 SGEN_TV_DECLARE (atv);
421 SGEN_TV_DECLARE (btv);
423 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
424 /*FIXME we should have a bit on each block/los object telling if the object have marked cards.*/
426 sgen_major_collector_iterate_block_ranges (move_cards_to_shadow_table);
427 sgen_los_iterate_live_block_ranges (move_cards_to_shadow_table);
428 sgen_wbroots_iterate_live_block_ranges (move_cards_to_shadow_table);
431 sgen_card_table_clear_cards ();
433 SGEN_TV_GETTIME (atv);
434 sgen_get_major_collector ()->scan_card_table (CARDTABLE_SCAN_GLOBAL, ctx, 0, 1);
435 SGEN_TV_GETTIME (btv);
436 last_major_scan_time = SGEN_TV_ELAPSED (atv, btv);
437 major_card_scan_time += last_major_scan_time;
438 sgen_los_scan_card_table (CARDTABLE_SCAN_GLOBAL, ctx, 0, 1);
439 SGEN_TV_GETTIME (atv);
440 last_los_scan_time = SGEN_TV_ELAPSED (btv, atv);
441 los_card_scan_time += last_los_scan_time;
443 sgen_wbroots_scan_card_table (ctx);
447 sgen_get_card_table_configuration (int *shift_bits, gpointer *mask)
449 #ifndef MANAGED_WBARRIER
455 *shift_bits = CARD_BITS;
456 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
457 *mask = (gpointer)CARD_MASK;
462 return sgen_cardtable;
468 sgen_card_table_dump_obj_card (GCObject *object, size_t size, void *dummy)
470 guint8 *start = sgen_card_table_get_card_scan_address (object);
471 guint8 *end = start + sgen_card_table_number_of_cards_in_range (object, size);
473 printf ("--obj %p %d cards [%p %p]--", object, size, start, end);
474 for (; start < end; ++start) {
476 printf ("\n\t[%p] ", start);
477 printf ("%x ", *start);
490 #define MWORD_MASK (sizeof (mword) - 1)
493 find_card_offset (mword card)
495 /*XXX Use assembly as this generates some pretty bad code */
496 #if (defined(__i386__) || defined(__arm__)) && defined(__GNUC__)
497 return (__builtin_ffs (card) - 1) / 8;
498 #elif (defined(__x86_64__) || defined(__aarch64__)) && defined(__GNUC__)
499 return (__builtin_ffsll (card) - 1) / 8;
500 #elif defined(__s390x__)
501 return (__builtin_ffsll (GUINT64_TO_LE(card)) - 1) / 8;
504 guint8 *ptr = (guint8 *) &card;
505 for (i = 0; i < sizeof (mword); ++i) {
514 sgen_find_next_card (guint8 *card_data, guint8 *end)
516 mword *cards, *cards_end;
519 while ((((mword)card_data) & MWORD_MASK) && card_data < end) {
525 if (card_data == end)
528 cards = (mword*)card_data;
529 cards_end = (mword*)((mword)end & ~MWORD_MASK);
530 while (cards < cards_end) {
533 return (guint8*)cards + find_card_offset (card);
537 card_data = (guint8*)cards_end;
538 while (card_data < end) {
548 sgen_cardtable_scan_object (GCObject *obj, mword block_obj_size, guint8 *cards, ScanCopyContext ctx)
550 HEAVY_STAT (++large_objects);
552 if (sgen_client_cardtable_scan_object (obj, cards, ctx))
555 HEAVY_STAT (++bloby_objects);
557 if (sgen_card_table_is_range_marked (cards, (mword)obj, block_obj_size))
558 ctx.ops->scan_object (obj, sgen_obj_get_descriptor (obj), ctx.queue);
559 } else if (sgen_card_table_region_begin_scanning ((mword)obj, block_obj_size)) {
560 ctx.ops->scan_object (obj, sgen_obj_get_descriptor (obj), ctx.queue);
563 binary_protocol_card_scan (obj, sgen_safe_object_get_size (obj));
567 sgen_card_table_init (SgenRememberedSet *remset)
569 sgen_cardtable = (guint8 *)sgen_alloc_os_memory (CARD_COUNT_IN_BYTES, (SgenAllocFlags)(SGEN_ALLOC_INTERNAL | SGEN_ALLOC_ACTIVATE), "card table", MONO_MEM_ACCOUNT_SGEN_CARD_TABLE);
571 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
572 sgen_shadow_cardtable = (guint8 *)sgen_alloc_os_memory (CARD_COUNT_IN_BYTES, (SgenAllocFlags)(SGEN_ALLOC_INTERNAL | SGEN_ALLOC_ACTIVATE), "shadow card table", MONO_MEM_ACCOUNT_SGEN_SHADOW_CARD_TABLE);
575 #ifdef HEAVY_STATISTICS
576 mono_counters_register ("marked cards", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &marked_cards);
577 mono_counters_register ("scanned cards", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &scanned_cards);
578 mono_counters_register ("remarked cards", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &remarked_cards);
580 mono_counters_register ("cardtable scanned objects", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &scanned_objects);
581 mono_counters_register ("cardtable large objects", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &large_objects);
582 mono_counters_register ("cardtable bloby objects", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &bloby_objects);
584 mono_counters_register ("cardtable major scan time", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &major_card_scan_time);
585 mono_counters_register ("cardtable los scan time", MONO_COUNTER_GC | MONO_COUNTER_ULONG | MONO_COUNTER_TIME, &los_card_scan_time);
588 remset->wbarrier_set_field = sgen_card_table_wbarrier_set_field;
589 remset->wbarrier_arrayref_copy = sgen_card_table_wbarrier_arrayref_copy;
590 remset->wbarrier_value_copy = sgen_card_table_wbarrier_value_copy;
591 remset->wbarrier_object_copy = sgen_card_table_wbarrier_object_copy;
592 remset->wbarrier_generic_nostore = sgen_card_table_wbarrier_generic_nostore;
593 remset->record_pointer = sgen_card_table_record_pointer;
595 remset->scan_remsets = sgen_card_table_scan_remsets;
597 remset->clear_cards = sgen_card_table_clear_cards;
599 remset->find_address = sgen_card_table_find_address;
600 remset->find_address_with_cards = sgen_card_table_find_address_with_cards;
602 need_mod_union = sgen_get_major_collector ()->is_concurrent;
605 #endif /*HAVE_SGEN_GC*/