void V8GCController::gcEpilogue(v8::GCType type, v8::GCCallbackFlags flags)
{
// FIXME: It would be nice if the GC callbacks passed the Isolate directly....
v8::Isolate* isolate = v8::Isolate::GetCurrent();
if (type == v8::kGCTypeScavenge)
minorGCEpilogue(isolate);
else if (type == v8::kGCTypeMarkSweepCompact)
majorGCEpilogue(isolate);
// Forces a Blink heap garbage collection when a garbage collection
// was forced from V8. This is used for tests that force GCs from
// JavaScript to verify that objects die when expected.
if (flags & v8::kGCCallbackFlagForced) {
// This single GC is not enough for two reasons:
// (1) The GC is not precise because the GC scans on-stack pointers conservatively.
// (2) One GC is not enough to break a chain of persistent handles. It's possible that
// some heap allocated objects own objects that contain persistent handles
// pointing to other heap allocated objects. To break the chain, we need multiple GCs.
//
// Regarding (1), we force a precise GC at the end of the current event loop. So if you want
// to collect all garbage, you need to wait until the next event loop.
// Regarding (2), it would be OK in practice to trigger only one GC per gcEpilogue, because
// GCController.collectAll() forces 7 V8's GC.
Heap::collectGarbage(ThreadState::HeapPointersOnStack, ThreadState::ForcedGC);
// Forces a precise GC at the end of the current event loop.
Heap::setForcePreciseGCForTesting();
}
TRACE_EVENT_END1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "GCEvent", "usedHeapSizeAfter", usedHeapSize(isolate));
TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "UpdateCounters", "data", InspectorUpdateCountersEvent::data());
}
void V8GCController::gcEpilogue(v8::Isolate* isolate, v8::GCType type, v8::GCCallbackFlags flags)
{
switch (type) {
case v8::kGCTypeScavenge:
TRACE_EVENT_END1("devtools.timeline,v8", "MinorGC", "usedHeapSizeAfter", usedHeapSize(isolate));
// TODO(haraken): Remove this. See the comment in gcPrologue.
if (ThreadState::current())
ThreadState::current()->scheduleV8FollowupGCIfNeeded(BlinkGC::V8MinorGC);
break;
case v8::kGCTypeMarkSweepCompact:
TRACE_EVENT_END1("devtools.timeline,v8", "MajorGC", "usedHeapSizeAfter", usedHeapSize(isolate));
if (ThreadState::current())
ThreadState::current()->scheduleV8FollowupGCIfNeeded(BlinkGC::V8MajorGC);
break;
case v8::kGCTypeIncrementalMarking:
TRACE_EVENT_END1("devtools.timeline,v8", "MajorGC", "usedHeapSizeAfter", usedHeapSize(isolate));
break;
case v8::kGCTypeProcessWeakCallbacks:
TRACE_EVENT_END1("devtools.timeline,v8", "MajorGC", "usedHeapSizeAfter", usedHeapSize(isolate));
break;
default:
ASSERT_NOT_REACHED();
}
if (isMainThread())
ScriptForbiddenScope::exit();
// v8::kGCCallbackFlagForced forces a Blink heap garbage collection
// when a garbage collection was forced from V8. This is either used
// for tests that force GCs from JavaScript to verify that objects die
// when expected.
if (flags & v8::kGCCallbackFlagForced) {
// This single GC is not enough for two reasons:
// (1) The GC is not precise because the GC scans on-stack pointers conservatively.
// (2) One GC is not enough to break a chain of persistent handles. It's possible that
// some heap allocated objects own objects that contain persistent handles
// pointing to other heap allocated objects. To break the chain, we need multiple GCs.
//
// Regarding (1), we force a precise GC at the end of the current event loop. So if you want
// to collect all garbage, you need to wait until the next event loop.
// Regarding (2), it would be OK in practice to trigger only one GC per gcEpilogue, because
// GCController.collectAll() forces multiple V8's GC.
Heap::collectGarbage(BlinkGC::HeapPointersOnStack, BlinkGC::GCWithSweep, BlinkGC::ForcedGC);
// Forces a precise GC at the end of the current event loop.
if (ThreadState::current()) {
RELEASE_ASSERT(!ThreadState::current()->isInGC());
ThreadState::current()->setGCState(ThreadState::FullGCScheduled);
}
}
// v8::kGCCallbackFlagCollectAllAvailableGarbage is used when V8 handles
// low memory notifications.
if (flags & v8::kGCCallbackFlagCollectAllAvailableGarbage) {
// This single GC is not enough. See the above comment.
Heap::collectGarbage(BlinkGC::HeapPointersOnStack, BlinkGC::GCWithSweep, BlinkGC::ForcedGC);
// Do not force a precise GC at the end of the current event loop.
// According to UMA stats, the collection rate of the precise GC
// scheduled at the end of the low memory handling is extremely low,
// because the above conservative GC is sufficient for collecting
// most objects. So we intentionally don't schedule a precise GC here.
}
TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "UpdateCounters", TRACE_EVENT_SCOPE_THREAD, "data", InspectorUpdateCountersEvent::data());
}
