2 * sgen-cardtable.c: Card table implementation for sgen
5 * Rodrigo Kumpera (rkumpera@novell.com)
7 * SGen is licensed under the terms of the MIT X11 license
9 * Copyright 2001-2003 Ximian, Inc
10 * Copyright 2003-2010 Novell, Inc.
11 * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
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33 #ifdef SGEN_HAVE_CARDTABLE
35 //#define CARDTABLE_STATS
38 #ifdef HAVE_SYS_MMAN_H
41 #include <sys/types.h>
43 guint8 *sgen_cardtable;
46 #ifdef HEAVY_STATISTICS
47 long long marked_cards;
48 long long scanned_cards;
49 long long scanned_objects;
50 long long remarked_cards;
52 static long long los_marked_cards;
53 static long long large_objects;
54 static long long bloby_objects;
55 static long long los_array_cards;
56 static long long los_array_remsets;
59 static long long major_card_scan_time;
60 static long long los_card_scan_time;
62 static long long last_major_scan_time;
63 static long long last_los_scan_time;
64 /*WARNING: This function returns the number of cards regardless of overflow in case of overlapping cards.*/
66 cards_in_range (mword address, mword size)
68 mword end = address + MAX (1, size) - 1;
69 return (end >> CARD_BITS) - (address >> CARD_BITS) + 1;
72 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
74 guint8 *sgen_shadow_cardtable;
76 #define SGEN_SHADOW_CARDTABLE_END (sgen_shadow_cardtable + CARD_COUNT_IN_BYTES)
77 #define SGEN_CARDTABLE_END (sgen_cardtable + CARD_COUNT_IN_BYTES)
80 sgen_card_table_region_begin_scanning (mword start, mword end)
82 /*XXX this can be improved to work on words and have a single loop induction var */
83 while (start <= end) {
84 if (sgen_card_table_card_begin_scanning (start))
86 start += CARD_SIZE_IN_BYTES;
94 sgen_card_table_region_begin_scanning (mword start, mword size)
97 guint8 *card = sgen_card_table_get_card_address (start);
98 guint8 *end = card + cards_in_range (start, size);
100 /*XXX this can be improved to work on words and have a branchless body */
101 while (card != end) {
108 memset (sgen_card_table_get_card_address (start), 0, size >> CARD_BITS);
115 /*FIXME this assumes that major blocks are multiple of 4K which is pretty reasonable */
117 sgen_card_table_get_card_data (guint8 *data_dest, mword address, mword cards)
119 mword *start = (mword*)sgen_card_table_get_card_scan_address (address);
120 mword *dest = (mword*)data_dest;
121 mword *end = (mword*)(data_dest + cards);
124 for (; dest < end; ++dest, ++start) {
129 #ifndef SGEN_HAVE_OVERLAPPING_CARDS
138 sgen_card_table_address_is_marked (mword address)
140 return *sgen_card_table_get_card_address (address) != 0;
144 sgen_card_table_mark_address (mword address)
146 *sgen_card_table_get_card_address (address) = 1;
150 sgen_card_table_align_pointer (void *ptr)
152 return (void*)((mword)ptr & ~(CARD_SIZE_IN_BYTES - 1));
156 sgen_card_table_mark_range (mword address, mword size)
158 memset (sgen_card_table_get_card_address (address), 1, cards_in_range (address, size));
162 sgen_card_table_is_range_marked (guint8 *cards, mword address, mword size)
164 guint8 *end = cards + cards_in_range (address, size);
166 /*This is safe since this function is only called by code that only passes continuous card blocks*/
167 while (cards != end) {
176 card_table_init (void)
178 sgen_cardtable = mono_sgen_alloc_os_memory (CARD_COUNT_IN_BYTES, TRUE);
180 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
181 sgen_shadow_cardtable = mono_sgen_alloc_os_memory (CARD_COUNT_IN_BYTES, TRUE);
184 #ifdef HEAVY_STATISTICS
185 mono_counters_register ("marked cards", MONO_COUNTER_GC | MONO_COUNTER_LONG, &marked_cards);
186 mono_counters_register ("scanned cards", MONO_COUNTER_GC | MONO_COUNTER_LONG, &scanned_cards);
187 mono_counters_register ("remarked cards", MONO_COUNTER_GC | MONO_COUNTER_LONG, &remarked_cards);
189 mono_counters_register ("los marked cards", MONO_COUNTER_GC | MONO_COUNTER_LONG, &los_marked_cards);
190 mono_counters_register ("los array cards scanned ", MONO_COUNTER_GC | MONO_COUNTER_LONG, &los_array_cards);
191 mono_counters_register ("los array remsets", MONO_COUNTER_GC | MONO_COUNTER_LONG, &los_array_remsets);
192 mono_counters_register ("cardtable scanned objects", MONO_COUNTER_GC | MONO_COUNTER_LONG, &scanned_objects);
193 mono_counters_register ("cardtable large objects", MONO_COUNTER_GC | MONO_COUNTER_LONG, &large_objects);
194 mono_counters_register ("cardtable bloby objects", MONO_COUNTER_GC | MONO_COUNTER_LONG, &bloby_objects);
196 mono_counters_register ("cardtable major scan time", MONO_COUNTER_GC | MONO_COUNTER_LONG, &major_card_scan_time);
197 mono_counters_register ("cardtable los scan time", MONO_COUNTER_GC | MONO_COUNTER_LONG, &los_card_scan_time);
200 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
203 move_cards_to_shadow_table (mword start, mword size)
205 guint8 *from = sgen_card_table_get_card_address (start);
206 guint8 *to = sgen_card_table_get_shadow_card_address (start);
207 size_t bytes = cards_in_range (start, size);
209 if (to + bytes > SGEN_SHADOW_CARDTABLE_END) {
210 size_t first_chunk = SGEN_SHADOW_CARDTABLE_END - to;
211 size_t second_chunk = MIN (CARD_COUNT_IN_BYTES, bytes) - first_chunk;
213 memcpy (to, from, first_chunk);
214 memcpy (sgen_shadow_cardtable, sgen_cardtable, second_chunk);
216 memcpy (to, from, bytes);
221 clear_cards (mword start, mword size)
223 guint8 *addr = sgen_card_table_get_card_address (start);
224 size_t bytes = cards_in_range (start, size);
226 if (addr + bytes > SGEN_CARDTABLE_END) {
227 size_t first_chunk = SGEN_CARDTABLE_END - addr;
229 memset (addr, 0, first_chunk);
230 memset (sgen_cardtable, 0, bytes - first_chunk);
232 memset (addr, 0, bytes);
240 clear_cards (mword start, mword size)
242 memset (sgen_card_table_get_card_address (start), 0, cards_in_range (start, size));
249 card_table_clear (void)
251 /*XXX we could do this in 2 ways. using mincore or iterating over all sections/los objects */
253 major_collector.iterate_live_block_ranges (clear_cards);
254 mono_sgen_los_iterate_live_block_ranges (clear_cards);
258 scan_from_card_tables (void *start_nursery, void *end_nursery, GrayQueue *queue)
264 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
265 /*FIXME we should have a bit on each block/los object telling if the object have marked cards.*/
267 major_collector.iterate_live_block_ranges (move_cards_to_shadow_table);
268 mono_sgen_los_iterate_live_block_ranges (move_cards_to_shadow_table);
274 major_collector.scan_card_table (queue);
276 last_major_scan_time = TV_ELAPSED_MS (atv, btv);
277 major_card_scan_time += last_major_scan_time;
278 mono_sgen_los_scan_card_table (queue);
280 last_los_scan_time = TV_ELAPSED_MS (btv, atv);
281 los_card_scan_time += last_los_scan_time;
286 mono_gc_get_card_table (int *shift_bits, gpointer *mask)
291 g_assert (sgen_cardtable);
292 *shift_bits = CARD_BITS;
293 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
294 *mask = (gpointer)CARD_MASK;
299 return sgen_cardtable;
304 collect_faulted_cards (void)
306 #define CARD_PAGES (CARD_COUNT_IN_BYTES / 4096)
308 unsigned char faulted [CARD_PAGES] = { 0 };
309 mincore (sgen_cardtable, CARD_COUNT_IN_BYTES, faulted);
311 for (i = 0; i < CARD_PAGES; ++i) {
316 printf ("TOTAL card pages %d faulted %d\n", CARD_PAGES, count);
320 sgen_card_table_dump_obj_card (char *object, size_t size, void *dummy)
322 guint8 *start = sgen_card_table_get_card_scan_address (object);
323 guint8 *end = start + cards_in_range (object, size);
325 printf ("--obj %p %d cards [%p %p]--", object, size, start, end);
326 for (; start < end; ++start) {
328 printf ("\n\t[%p] ", start);
329 printf ("%x ", *start);
338 #define MWORD_MASK (sizeof (mword) - 1)
341 find_card_offset (mword card)
343 /*XXX Use assembly as this generates some pretty bad code */
344 #if defined(__i386__) && defined(__GNUC__)
345 return (__builtin_ffs (card) - 1) / 8;
346 #elif defined(__x86_64__) && defined(__GNUC__)
347 return (__builtin_ffsll (card) - 1) / 8;
348 #elif defined(__s390x__)
349 return (__builtin_ffsll (GUINT64_TO_LE(card)) - 1) / 8;
352 guint8 *ptr = (guint *) &card;
353 for (i = 0; i < sizeof (mword); ++i) {
362 find_next_card (guint8 *card_data, guint8 *end)
364 mword *cards, *cards_end;
367 while ((((mword)card_data) & MWORD_MASK) && card_data < end) {
373 if (card_data == end)
376 cards = (mword*)card_data;
377 cards_end = (mword*)((mword)end & ~MWORD_MASK);
378 while (cards < cards_end) {
381 return (guint8*)cards + find_card_offset (card);
385 card_data = (guint8*)cards_end;
386 while (card_data < end) {
396 sgen_cardtable_scan_object (char *obj, mword block_obj_size, guint8 *cards, SgenGrayQueue *queue)
398 MonoVTable *vt = (MonoVTable*)LOAD_VTABLE (obj);
399 MonoClass *klass = vt->klass;
400 CopyOrMarkObjectFunc copy_func = mono_sgen_get_copy_object ();
401 ScanObjectFunc scan_object_func = mono_sgen_get_minor_scan_object ();
402 ScanVTypeFunc scan_vtype_func = mono_sgen_get_minor_scan_vtype ();
404 HEAVY_STAT (++large_objects);
406 if (!SGEN_VTABLE_HAS_REFERENCES (vt))
410 guint8 *card_data, *card_base;
411 guint8 *card_data_end;
412 char *obj_start = sgen_card_table_align_pointer (obj);
413 mword obj_size = mono_sgen_par_object_get_size (vt, (MonoObject*)obj);
414 char *obj_end = obj + obj_size;
418 MonoArray *arr = (MonoArray*)obj;
419 mword desc = (mword)klass->element_class->gc_descr;
420 int elem_size = mono_array_element_size (klass);
422 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
423 guint8 *overflow_scan_end = NULL;
429 card_data = sgen_card_table_get_card_scan_address ((mword)obj);
431 card_base = card_data;
432 card_count = cards_in_range ((mword)obj, obj_size);
433 card_data_end = card_data + card_count;
436 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
437 /*Check for overflow and if so, setup to scan in two steps*/
438 if (!cards && card_data_end >= SGEN_SHADOW_CARDTABLE_END) {
439 overflow_scan_end = sgen_shadow_cardtable + (card_data_end - SGEN_SHADOW_CARDTABLE_END);
440 card_data_end = SGEN_SHADOW_CARDTABLE_END;
446 card_data = find_next_card (card_data, card_data_end);
447 for (; card_data < card_data_end; card_data = find_next_card (card_data + 1, card_data_end)) {
449 int idx = (card_data - card_base) + extra_idx;
450 char *start = (char*)(obj_start + idx * CARD_SIZE_IN_BYTES);
451 char *card_end = start + CARD_SIZE_IN_BYTES;
454 HEAVY_STAT (++los_marked_cards);
457 sgen_card_table_prepare_card_for_scanning (card_data);
459 card_end = MIN (card_end, obj_end);
461 if (start <= (char*)arr->vector)
464 index = ARRAY_OBJ_INDEX (start, obj, elem_size);
466 elem = (char*)mono_array_addr_with_size ((MonoArray*)obj, elem_size, index);
467 if (klass->element_class->valuetype) {
468 for (; elem < card_end; elem += elem_size)
469 scan_vtype_func (elem, desc, queue);
471 HEAVY_STAT (++los_array_cards);
472 for (; elem < card_end; elem += SIZEOF_VOID_P) {
473 gpointer new, old = *(gpointer*)elem;
474 if (G_UNLIKELY (ptr_in_nursery (old))) {
475 HEAVY_STAT (++los_array_remsets);
476 copy_func ((void**)elem, queue);
477 new = *(gpointer*)elem;
478 if (G_UNLIKELY (ptr_in_nursery (new)))
479 mono_sgen_add_to_global_remset (elem);
485 #ifdef SGEN_HAVE_OVERLAPPING_CARDS
486 if (overflow_scan_end) {
487 extra_idx = card_data - card_base;
488 card_base = card_data = sgen_shadow_cardtable;
489 card_data_end = overflow_scan_end;
490 overflow_scan_end = NULL;
496 HEAVY_STAT (++bloby_objects);
498 if (sgen_card_table_is_range_marked (cards, (mword)obj, block_obj_size))
499 scan_object_func (obj, queue);
500 } else if (sgen_card_table_region_begin_scanning ((mword)obj, block_obj_size)) {
501 scan_object_func (obj, queue);
506 #ifdef CARDTABLE_STATS
509 int total, marked, remarked;
512 static card_stats major_stats, los_stats;
513 static card_stats *cur_stats;
516 count_marked_cards (mword start, mword size)
518 mword end = start + size;
519 while (start <= end) {
521 if (sgen_card_table_address_is_marked (start))
523 start += CARD_SIZE_IN_BYTES;
528 count_remarked_cards (mword start, mword size)
530 mword end = start + size;
531 while (start <= end) {
532 if (sgen_card_table_address_is_marked (start))
533 ++cur_stats->remarked;
534 start += CARD_SIZE_IN_BYTES;
541 card_tables_collect_stats (gboolean begin)
543 #ifdef CARDTABLE_STATS
545 memset (&major_stats, 0, sizeof (card_stats));
546 memset (&los_stats, 0, sizeof (card_stats));
547 cur_stats = &major_stats;
548 major_collector.iterate_live_block_ranges (count_marked_cards);
549 cur_stats = &los_stats;
550 mono_sgen_los_iterate_live_block_ranges (count_marked_cards);
552 cur_stats = &major_stats;
553 major_collector.iterate_live_block_ranges (count_marked_cards);
554 cur_stats = &los_stats;
555 mono_sgen_los_iterate_live_block_ranges (count_remarked_cards);
556 printf ("cards major (t %d m %d r %d) los (t %d m %d r %d) major_scan %lld los_scan %lld\n",
557 major_stats.total, major_stats.marked, major_stats.remarked,
558 los_stats.total, los_stats.marked, los_stats.remarked,
559 last_major_scan_time, last_los_scan_time);
567 sgen_card_table_mark_address (mword address)
569 g_assert_not_reached ();
573 sgen_card_table_mark_range (mword address, mword size)
575 g_assert_not_reached ();
578 #define sgen_card_table_address_is_marked(p) FALSE
579 #define scan_from_card_tables(start,end,queue)
580 #define card_table_clear()
581 #define card_table_init()
582 #define card_tables_collect_stats(begin)
585 mono_gc_get_card_table (int *shift_bits, gpointer *mask)