/**
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* \file
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* Card table implementation for sgen
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*
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* Author:
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* Rodrigo Kumpera (rkumpera@novell.com)
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*
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* Copyright 2001-2003 Ximian, Inc
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* Copyright 2003-2010 Novell, Inc.
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* Copyright 2011 Xamarin Inc (http://www.xamarin.com)
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* Copyright (C) 2012 Xamarin Inc
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*
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* Licensed under the MIT license. See LICENSE file in the project root for full license information.
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*/
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#include "config.h"
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#ifdef HAVE_SGEN_GC
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#include <string.h>
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#include "mono/sgen/sgen-gc.h"
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#include "mono/sgen/sgen-cardtable.h"
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#include "mono/sgen/sgen-memory-governor.h"
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#include "mono/sgen/sgen-protocol.h"
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#include "mono/sgen/sgen-layout-stats.h"
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#include "mono/sgen/sgen-client.h"
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#include "mono/sgen/gc-internal-agnostic.h"
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#include "mono/utils/mono-memory-model.h"
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//#define CARDTABLE_STATS
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#ifdef HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#ifdef HAVE_SYS_MMAN_H
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#include <sys/mman.h>
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#endif
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#include <sys/types.h>
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guint8 *sgen_cardtable;
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static gboolean need_mod_union;
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#ifdef HEAVY_STATISTICS
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guint64 marked_cards;
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guint64 scanned_cards;
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guint64 scanned_objects;
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guint64 remarked_cards;
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static guint64 large_objects;
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static guint64 bloby_objects;
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#endif
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mword
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sgen_card_table_number_of_cards_in_range (mword address, mword size)
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{
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mword end = address + MAX (1, size) - 1;
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return (end >> CARD_BITS) - (address >> CARD_BITS) + 1;
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}
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static void
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sgen_card_table_wbarrier_set_field (GCObject *obj, gpointer field_ptr, GCObject* value)
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{
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*(void**)field_ptr = value;
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if (need_mod_union || sgen_ptr_in_nursery (value))
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sgen_card_table_mark_address ((mword)field_ptr);
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sgen_dummy_use (value);
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}
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static void
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sgen_card_table_wbarrier_arrayref_copy (gpointer dest_ptr, gpointer src_ptr, int count)
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{
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gpointer *dest = (gpointer *)dest_ptr;
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gpointer *src = (gpointer *)src_ptr;
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/*overlapping that required backward copying*/
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if (src < dest && (src + count) > dest) {
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gpointer *start = dest;
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dest += count - 1;
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src += count - 1;
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for (; dest >= start; --src, --dest) {
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gpointer value = *src;
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SGEN_UPDATE_REFERENCE_ALLOW_NULL (dest, value);
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if (need_mod_union || sgen_ptr_in_nursery (value))
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sgen_card_table_mark_address ((mword)dest);
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sgen_dummy_use (value);
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}
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} else {
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gpointer *end = dest + count;
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for (; dest < end; ++src, ++dest) {
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gpointer value = *src;
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SGEN_UPDATE_REFERENCE_ALLOW_NULL (dest, value);
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if (need_mod_union || sgen_ptr_in_nursery (value))
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sgen_card_table_mark_address ((mword)dest);
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sgen_dummy_use (value);
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}
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}
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}
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static void
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sgen_card_table_wbarrier_value_copy (gpointer dest, gpointer src, int count, size_t element_size)
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{
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size_t size = count * element_size;
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TLAB_ACCESS_INIT;
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ENTER_CRITICAL_REGION;
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mono_gc_memmove_atomic (dest, src, size);
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sgen_card_table_mark_range ((mword)dest, size);
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EXIT_CRITICAL_REGION;
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}
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static void
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sgen_card_table_wbarrier_object_copy (GCObject* obj, GCObject *src)
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{
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size_t size = sgen_client_par_object_get_size (SGEN_LOAD_VTABLE_UNCHECKED (obj), obj);
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TLAB_ACCESS_INIT;
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ENTER_CRITICAL_REGION;
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mono_gc_memmove_aligned ((char*)obj + SGEN_CLIENT_OBJECT_HEADER_SIZE, (char*)src + SGEN_CLIENT_OBJECT_HEADER_SIZE,
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size - SGEN_CLIENT_OBJECT_HEADER_SIZE);
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sgen_card_table_mark_range ((mword)obj, size);
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EXIT_CRITICAL_REGION;
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}
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static void
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sgen_card_table_wbarrier_generic_nostore (gpointer ptr)
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{
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sgen_card_table_mark_address ((mword)ptr);
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}
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static void
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sgen_card_table_wbarrier_range_copy (gpointer _dest, gpointer _src, int size)
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{
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GCObject **dest = (GCObject **)_dest;
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GCObject **src = (GCObject **)_src;
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size_t nursery_bits = sgen_nursery_bits;
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char *start = sgen_nursery_start;
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G_GNUC_UNUSED char *end = sgen_nursery_end;
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/*
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* It's cardtable theory time!
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* Our cardtable scanning code supports marking any card that an object/valuetype belongs to.
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* This function is supposed to be used to copy a range that fully belongs to a single type.
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* It must not be used, for example, to copy 2 adjacent VTs in an array.
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*/
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volatile guint8 *card_address = (volatile guint8 *)sgen_card_table_get_card_address ((mword)dest);
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while (size) {
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GCObject *value = *src;
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*dest = value;
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if (SGEN_PTR_IN_NURSERY (value, nursery_bits, start, end) || concurrent_collection_in_progress) {
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*card_address = 1;
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sgen_dummy_use (value);
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}
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++src;
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++dest;
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size -= SIZEOF_VOID_P;
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}
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}
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#ifdef SGEN_HAVE_OVERLAPPING_CARDS
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guint8 *sgen_shadow_cardtable;
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#define SGEN_CARDTABLE_END (sgen_cardtable + CARD_COUNT_IN_BYTES)
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static gboolean
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sgen_card_table_region_begin_scanning (mword start, mword size)
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{
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mword end = start + size;
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/*XXX this can be improved to work on words and have a single loop induction var */
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while (start < end) {
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if (sgen_card_table_card_begin_scanning (start))
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return TRUE;
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start += CARD_SIZE_IN_BYTES;
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}
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return FALSE;
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}
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#else
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static gboolean
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sgen_card_table_region_begin_scanning (mword start, mword size)
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{
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gboolean res = FALSE;
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guint8 *card = sgen_card_table_get_card_address (start);
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guint8 *end = card + sgen_card_table_number_of_cards_in_range (start, size);
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/*XXX this can be improved to work on words and have a branchless body */
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while (card != end) {
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if (*card++) {
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res = TRUE;
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break;
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}
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}
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memset (sgen_card_table_get_card_address (start), 0, size >> CARD_BITS);
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return res;
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}
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#endif
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/*FIXME this assumes that major blocks are multiple of 4K which is pretty reasonable */
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gboolean
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sgen_card_table_get_card_data (guint8 *data_dest, mword address, mword cards)
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{
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mword *start = (mword*)sgen_card_table_get_card_scan_address (address);
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mword *dest = (mword*)data_dest;
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mword *end = (mword*)(data_dest + cards);
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mword mask = 0;
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for (; dest < end; ++dest, ++start) {
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mword v = *start;
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*dest = v;
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mask |= v;
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#ifndef SGEN_HAVE_OVERLAPPING_CARDS
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*start = 0;
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#endif
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}
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return mask != 0;
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}
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void*
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sgen_card_table_align_pointer (void *ptr)
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{
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return (void*)((mword)ptr & ~(CARD_SIZE_IN_BYTES - 1));
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}
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void
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sgen_card_table_mark_range (mword address, mword size)
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{
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mword num_cards = sgen_card_table_number_of_cards_in_range (address, size);
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guint8 *start = sgen_card_table_get_card_address (address);
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#ifdef SGEN_HAVE_OVERLAPPING_CARDS
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/*
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* FIXME: There's a theoretical bug here, namely that the card table is allocated so
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* far toward the end of the address space that start + num_cards overflows.
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*/
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guint8 *end = start + num_cards;
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SGEN_ASSERT (0, num_cards <= CARD_COUNT_IN_BYTES, "How did we get an object larger than the card table?");
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if (end > SGEN_CARDTABLE_END) {
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memset (start, 1, SGEN_CARDTABLE_END - start);
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memset (sgen_cardtable, 1, end - SGEN_CARDTABLE_END);
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return;
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}
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#endif
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memset (start, 1, num_cards);
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}
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static gboolean
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sgen_card_table_is_range_marked (guint8 *cards, mword address, mword size)
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{
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guint8 *end = cards + sgen_card_table_number_of_cards_in_range (address, size);
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/*This is safe since this function is only called by code that only passes continuous card blocks*/
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while (cards != end) {
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if (*cards++)
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return TRUE;
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}
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return FALSE;
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}
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static void
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sgen_card_table_record_pointer (gpointer address)
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{
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*sgen_card_table_get_card_address ((mword)address) = 1;
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}
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static gboolean
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sgen_card_table_find_address (char *addr)
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{
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return sgen_card_table_address_is_marked ((mword)addr);
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}
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static gboolean
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sgen_card_table_find_address_with_cards (char *cards_start, guint8 *cards, char *addr)
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{
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cards_start = (char *)sgen_card_table_align_pointer (cards_start);
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return cards [(addr - cards_start) >> CARD_BITS];
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}
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static void
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update_mod_union (guint8 *dest, guint8 *start_card, size_t num_cards)
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{
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int i;
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/* Marking from another thread can happen while we mark here */
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for (i = 0; i < num_cards; ++i) {
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if (start_card [i])
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dest [i] = 1;
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}
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}
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guint8*
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sgen_card_table_alloc_mod_union (char *obj, mword obj_size)
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{
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size_t num_cards = sgen_card_table_number_of_cards_in_range ((mword) obj, obj_size);
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guint8 *mod_union = (guint8 *)sgen_alloc_internal_dynamic (num_cards, INTERNAL_MEM_CARDTABLE_MOD_UNION, TRUE);
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memset (mod_union, 0, num_cards);
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return mod_union;
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}
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void
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sgen_card_table_free_mod_union (guint8 *mod_union, char *obj, mword obj_size)
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{
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size_t num_cards = sgen_card_table_number_of_cards_in_range ((mword) obj, obj_size);
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sgen_free_internal_dynamic (mod_union, num_cards, INTERNAL_MEM_CARDTABLE_MOD_UNION);
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}
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void
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sgen_card_table_update_mod_union_from_cards (guint8 *dest, guint8 *start_card, size_t num_cards)
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{
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SGEN_ASSERT (0, dest, "Why don't we have a mod union?");
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update_mod_union (dest, start_card, num_cards);
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}
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void
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sgen_card_table_update_mod_union (guint8 *dest, char *obj, mword obj_size, size_t *out_num_cards)
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{
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guint8 *start_card = sgen_card_table_get_card_address ((mword)obj);
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#ifndef SGEN_HAVE_OVERLAPPING_CARDS
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guint8 *end_card = sgen_card_table_get_card_address ((mword)obj + obj_size - 1) + 1;
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#endif
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size_t num_cards;
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#ifdef SGEN_HAVE_OVERLAPPING_CARDS
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size_t rest;
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rest = num_cards = sgen_card_table_number_of_cards_in_range ((mword) obj, obj_size);
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while (start_card + rest > SGEN_CARDTABLE_END) {
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size_t count = SGEN_CARDTABLE_END - start_card;
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sgen_card_table_update_mod_union_from_cards (dest, start_card, count);
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dest += count;
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rest -= count;
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start_card = sgen_cardtable;
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}
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num_cards = rest;
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#else
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num_cards = end_card - start_card;
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#endif
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sgen_card_table_update_mod_union_from_cards (dest, start_card, num_cards);
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if (out_num_cards)
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*out_num_cards = num_cards;
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}
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/* Preclean cards and saves the cards that need to be scanned afterwards in cards_preclean */
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void
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sgen_card_table_preclean_mod_union (guint8 *cards, guint8 *cards_preclean, size_t num_cards)
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{
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size_t i;
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memcpy (cards_preclean, cards, num_cards);
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for (i = 0; i < num_cards; i++) {
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if (cards_preclean [i]) {
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cards [i] = 0;
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}
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}
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/*
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* When precleaning we need to make sure the card cleaning
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* takes place before the object is scanned. If we don't
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* do this we could finish scanning the object and, before
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* the cleaning of the card takes place, another thread
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* could dirty the object, mark the mod_union card only for
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* us to clean it back, without scanning the object again.
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*/
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mono_memory_barrier ();
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}
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#ifdef SGEN_HAVE_OVERLAPPING_CARDS
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static void
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move_cards_to_shadow_table (mword start, mword size)
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{
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guint8 *from = sgen_card_table_get_card_address (start);
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guint8 *to = sgen_card_table_get_shadow_card_address (start);
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size_t bytes = sgen_card_table_number_of_cards_in_range (start, size);
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if (bytes >= CARD_COUNT_IN_BYTES) {
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memcpy (sgen_shadow_cardtable, sgen_cardtable, CARD_COUNT_IN_BYTES);
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} else if (to + bytes > SGEN_SHADOW_CARDTABLE_END) {
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size_t first_chunk = SGEN_SHADOW_CARDTABLE_END - to;
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size_t second_chunk = MIN (CARD_COUNT_IN_BYTES, bytes) - first_chunk;
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memcpy (to, from, first_chunk);
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memcpy (sgen_shadow_cardtable, sgen_cardtable, second_chunk);
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} else {
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memcpy (to, from, bytes);
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}
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}
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static void
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clear_cards (mword start, mword size)
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{
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guint8 *addr = sgen_card_table_get_card_address (start);
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size_t bytes = sgen_card_table_number_of_cards_in_range (start, size);
|
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if (bytes >= CARD_COUNT_IN_BYTES) {
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memset (sgen_cardtable, 0, CARD_COUNT_IN_BYTES);
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} else if (addr + bytes > SGEN_CARDTABLE_END) {
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size_t first_chunk = SGEN_CARDTABLE_END - addr;
|
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memset (addr, 0, first_chunk);
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memset (sgen_cardtable, 0, bytes - first_chunk);
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} else {
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memset (addr, 0, bytes);
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}
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}
|
|
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#else
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static void
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clear_cards (mword start, mword size)
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{
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memset (sgen_card_table_get_card_address (start), 0, sgen_card_table_number_of_cards_in_range (start, size));
|
}
|
|
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#endif
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static void
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sgen_card_table_clear_cards (void)
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{
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/*XXX we could do this in 2 ways. using mincore or iterating over all sections/los objects */
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sgen_major_collector_iterate_block_ranges (clear_cards);
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sgen_los_iterate_live_block_ranges (clear_cards);
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sgen_wbroots_iterate_live_block_ranges (clear_cards);
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}
|
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static void
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sgen_card_table_start_scan_remsets (void)
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{
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#ifdef SGEN_HAVE_OVERLAPPING_CARDS
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/*FIXME we should have a bit on each block/los object telling if the object have marked cards.*/
|
/*First we copy*/
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sgen_major_collector_iterate_block_ranges (move_cards_to_shadow_table);
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sgen_los_iterate_live_block_ranges (move_cards_to_shadow_table);
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sgen_wbroots_iterate_live_block_ranges (move_cards_to_shadow_table);
|
|
/*Then we clear*/
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sgen_card_table_clear_cards ();
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#endif
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}
|
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guint8*
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sgen_get_card_table_configuration (int *shift_bits, gpointer *mask)
|
{
|
#ifndef MANAGED_WBARRIER
|
return NULL;
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#else
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if (!sgen_cardtable)
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return NULL;
|
|
*shift_bits = CARD_BITS;
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#ifdef SGEN_HAVE_OVERLAPPING_CARDS
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*mask = (gpointer)CARD_MASK;
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#else
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*mask = NULL;
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#endif
|
|
return sgen_cardtable;
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#endif
|
}
|
|
#if 0
|
void
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sgen_card_table_dump_obj_card (GCObject *object, size_t size, void *dummy)
|
{
|
guint8 *start = sgen_card_table_get_card_scan_address (object);
|
guint8 *end = start + sgen_card_table_number_of_cards_in_range (object, size);
|
int cnt = 0;
|
printf ("--obj %p %d cards [%p %p]--", object, size, start, end);
|
for (; start < end; ++start) {
|
if (cnt == 0)
|
printf ("\n\t[%p] ", start);
|
printf ("%x ", *start);
|
++cnt;
|
if (cnt == 8)
|
cnt = 0;
|
}
|
printf ("\n");
|
}
|
#endif
|
|
/*
|
* Cardtable scanning
|
*/
|
|
#define MWORD_MASK (sizeof (mword) - 1)
|
|
static inline int
|
find_card_offset (mword card)
|
{
|
/*XXX Use assembly as this generates some pretty bad code */
|
#if (defined(__i386__) || defined(__arm__)) && defined(__GNUC__)
|
return (__builtin_ffs (card) - 1) / 8;
|
#elif (defined(__x86_64__) || defined(__aarch64__)) && defined(__GNUC__)
|
return (__builtin_ffsll (card) - 1) / 8;
|
#elif defined(__s390x__)
|
return (__builtin_ffsll (GUINT64_TO_LE(card)) - 1) / 8;
|
#else
|
int i;
|
guint8 *ptr = (guint8 *) &card;
|
for (i = 0; i < sizeof (mword); ++i) {
|
if (ptr[i])
|
return i;
|
}
|
return 0;
|
#endif
|
}
|
|
guint8*
|
sgen_find_next_card (guint8 *card_data, guint8 *end)
|
{
|
mword *cards, *cards_end;
|
mword card;
|
|
while ((((mword)card_data) & MWORD_MASK) && card_data < end) {
|
if (*card_data)
|
return card_data;
|
++card_data;
|
}
|
|
if (card_data == end)
|
return end;
|
|
cards = (mword*)card_data;
|
cards_end = (mword*)((mword)end & ~MWORD_MASK);
|
while (cards < cards_end) {
|
card = *cards;
|
if (card)
|
return (guint8*)cards + find_card_offset (card);
|
++cards;
|
}
|
|
card_data = (guint8*)cards_end;
|
while (card_data < end) {
|
if (*card_data)
|
return card_data;
|
++card_data;
|
}
|
|
return end;
|
}
|
|
void
|
sgen_cardtable_scan_object (GCObject *obj, mword block_obj_size, guint8 *cards, ScanCopyContext ctx)
|
{
|
HEAVY_STAT (++large_objects);
|
|
if (sgen_client_cardtable_scan_object (obj, cards, ctx))
|
return;
|
|
HEAVY_STAT (++bloby_objects);
|
if (cards) {
|
if (sgen_card_table_is_range_marked (cards, (mword)obj, block_obj_size))
|
ctx.ops->scan_object (obj, sgen_obj_get_descriptor (obj), ctx.queue);
|
} else if (sgen_card_table_region_begin_scanning ((mword)obj, block_obj_size)) {
|
ctx.ops->scan_object (obj, sgen_obj_get_descriptor (obj), ctx.queue);
|
}
|
|
binary_protocol_card_scan (obj, sgen_safe_object_get_size (obj));
|
}
|
|
void
|
sgen_card_table_init (SgenRememberedSet *remset)
|
{
|
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);
|
|
#ifdef SGEN_HAVE_OVERLAPPING_CARDS
|
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);
|
#endif
|
|
#ifdef HEAVY_STATISTICS
|
mono_counters_register ("marked cards", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &marked_cards);
|
mono_counters_register ("scanned cards", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &scanned_cards);
|
mono_counters_register ("remarked cards", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &remarked_cards);
|
|
mono_counters_register ("cardtable scanned objects", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &scanned_objects);
|
mono_counters_register ("cardtable large objects", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &large_objects);
|
mono_counters_register ("cardtable bloby objects", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &bloby_objects);
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#endif
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remset->wbarrier_set_field = sgen_card_table_wbarrier_set_field;
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remset->wbarrier_arrayref_copy = sgen_card_table_wbarrier_arrayref_copy;
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remset->wbarrier_value_copy = sgen_card_table_wbarrier_value_copy;
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remset->wbarrier_object_copy = sgen_card_table_wbarrier_object_copy;
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remset->wbarrier_generic_nostore = sgen_card_table_wbarrier_generic_nostore;
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remset->record_pointer = sgen_card_table_record_pointer;
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remset->start_scan_remsets = sgen_card_table_start_scan_remsets;
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remset->clear_cards = sgen_card_table_clear_cards;
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remset->find_address = sgen_card_table_find_address;
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remset->find_address_with_cards = sgen_card_table_find_address_with_cards;
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remset->wbarrier_range_copy = sgen_card_table_wbarrier_range_copy;
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need_mod_union = sgen_get_major_collector ()->is_concurrent;
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}
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#endif /*HAVE_SGEN_GC*/
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