Reviewers: danno, Hannes Payer,
Description:
Implement and enable zapping of code space while sweeping.
[email protected],[email protected]
BUG=
Please review this at https://codereview.chromium.org/181513004/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+39, -7 lines):
M src/flag-definitions.h
M src/mark-compact.cc
Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index
13de6b56eedd5b171d2e8ba2768a3ac6998b9e2e..294553e40a80fe69bb85e0db4ddb325eed406741
100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -572,6 +572,8 @@ DEFINE_bool(cleanup_code_caches_at_gc, true,
DEFINE_bool(use_marking_progress_bar, true,
"Use a progress bar to scan large objects in increments when "
"incremental marking is active.")
+DEFINE_bool(zap_code_space, true,
+ "Zap free memory in code space with 0xCC while sweeping.")
DEFINE_int(random_seed, 0,
"Default seed for initializing random generator "
"(0, the default, means to use system random).")
Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index
89ce89ef77ebf66a98189d70a1f0599ed5371301..4314c9d7217dd952033678469f6ee8c2e78cb268
100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -3204,13 +3204,21 @@ enum SkipListRebuildingMode {
};
+enum FreeSpaceTreatmentMode {
+ IGNORE_FREE_SPACE,
+ ZAP_FREE_SPACE
+};
+
+
// Sweep a space precisely. After this has been done the space can
// be iterated precisely, hitting only the live objects. Code space
// is always swept precisely because we want to be able to iterate
// over it. Map space is swept precisely, because it is not compacted.
// Slots in live objects pointing into evacuation candidates are updated
// if requested.
-template<SweepingMode sweeping_mode, SkipListRebuildingMode skip_list_mode>
+template<SweepingMode sweeping_mode,
+ SkipListRebuildingMode skip_list_mode,
+ FreeSpaceTreatmentMode free_space_mode>
static void SweepPrecisely(PagedSpace* space,
Page* p,
ObjectVisitor* v) {
@@ -3244,6 +3252,9 @@ static void SweepPrecisely(PagedSpace* space,
for ( ; live_objects != 0; live_objects--) {
Address free_end = cell_base + offsets[live_index++] * kPointerSize;
if (free_end != free_start) {
+ if (free_space_mode == ZAP_FREE_SPACE) {
+ memset(free_start, 0xcc, static_cast<int>(free_end -
free_start));
+ }
space->Free(free_start, static_cast<int>(free_end - free_start));
#ifdef ENABLE_GDB_JIT_INTERFACE
if (FLAG_gdbjit && space->identity() == CODE_SPACE) {
@@ -3275,6 +3286,9 @@ static void SweepPrecisely(PagedSpace* space,
*cell = 0;
}
if (free_start != p->area_end()) {
+ if (free_space_mode == ZAP_FREE_SPACE) {
+ memset(free_start, 0xcc, static_cast<int>(p->area_end() -
free_start));
+ }
space->Free(free_start, static_cast<int>(p->area_end() - free_start));
#ifdef ENABLE_GDB_JIT_INTERFACE
if (FLAG_gdbjit && space->identity() == CODE_SPACE) {
@@ -3520,12 +3534,23 @@ void
MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
SweepConservatively<SWEEP_SEQUENTIALLY>(space, NULL, p);
break;
case OLD_POINTER_SPACE:
- SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS, IGNORE_SKIP_LIST>(
+ SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS,
+ IGNORE_SKIP_LIST,
+ IGNORE_FREE_SPACE>(
space, p, &updating_visitor);
break;
case CODE_SPACE:
- SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS,
REBUILD_SKIP_LIST>(
- space, p, &updating_visitor);
+ if (FLAG_zap_code_space) {
+ SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS,
+ REBUILD_SKIP_LIST,
+ ZAP_FREE_SPACE>(
+ space, p, &updating_visitor);
+ } else {
+ SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS,
+ REBUILD_SKIP_LIST,
+ IGNORE_FREE_SPACE>(
+ space, p, &updating_visitor);
+ }
break;
default:
UNREACHABLE();
@@ -4145,10 +4170,15 @@ void MarkCompactCollector::SweepSpace(PagedSpace*
space, SweeperType sweeper) {
PrintF("Sweeping 0x%" V8PRIxPTR " precisely.\n",
reinterpret_cast<intptr_t>(p));
}
- if (space->identity() == CODE_SPACE) {
- SweepPrecisely<SWEEP_ONLY, REBUILD_SKIP_LIST>(space, p, NULL);
+ if (space->identity() == CODE_SPACE && FLAG_zap_code_space) {
+ SweepPrecisely<SWEEP_ONLY, REBUILD_SKIP_LIST, ZAP_FREE_SPACE>(
+ space, p, NULL);
+ } else if (space->identity() == CODE_SPACE) {
+ SweepPrecisely<SWEEP_ONLY, REBUILD_SKIP_LIST, IGNORE_FREE_SPACE>(
+ space, p, NULL);
} else {
- SweepPrecisely<SWEEP_ONLY, IGNORE_SKIP_LIST>(space, p, NULL);
+ SweepPrecisely<SWEEP_ONLY, IGNORE_SKIP_LIST, IGNORE_FREE_SPACE>(
+ space, p, NULL);
}
pages_swept++;
break;
--
--
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