Reviewers: Erik Corry,
Message:
PTAL.
Description:
Implement high promotion mode for new space.
This mode drastically decreases pause times by limiting maximum capacity
of the young generation when mutators generate many long-lived objects.
It shrinks new space back to the initial capacity and keeps it at that
capacity until survival rate decreases again.
[email protected]
Please review this at http://codereview.chromium.org/8702006/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files:
M src/heap.h
M src/heap.cc
Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index
3d6db92eca1853b9c6b96cfae1204cbd1c205c5b..5bb64101544ef6d29f9e813eda05748259bc048a
100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -112,6 +112,7 @@ Heap::Heap()
disallow_allocation_failure_(false),
debug_utils_(NULL),
#endif // DEBUG
+ new_space_high_promotion_mode_active_(false),
old_gen_promotion_limit_(kMinimumPromotionLimit),
old_gen_allocation_limit_(kMinimumAllocationLimit),
old_gen_limit_factor_(1),
@@ -735,6 +736,32 @@ bool Heap::PerformGarbageCollection(GarbageCollector
collector,
UpdateSurvivalRateTrend(start_new_space_size);
+ if (!new_space_high_promotion_mode_active_ &&
+ new_space_.Capacity() == new_space_.MaximumCapacity() &&
+ IsStableOrIncreasingSurvivalTrend() &&
+ IsHighSurvivalRate()) {
+ // Stable high survival rates even though young generation is at
+ // maximum capacity indicates that most objects will be promoted.
+ // To decrease scavenger pauses and final mark-sweep pauses, we
+ // have to limit maximal capacity of the young generation.
+ new_space_high_promotion_mode_active_ = true;
+ if (FLAG_trace_gc) {
+ PrintF("Limited new space size due to high promotion rate: %d
MB\n",
+ new_space_.InitialCapacity() / MB);
+ }
+ } else if (new_space_high_promotion_mode_active_ &&
+ IsDecreasingSurvivalTrend() &&
+ !IsHighSurvivalRate()) {
+ // Decreasing low survival rates might indicate that the above high
+ // promotion mode is over and we should allow the young generation
+ // to grow again.
+ new_space_high_promotion_mode_active_ = false;
+ if (FLAG_trace_gc) {
+ PrintF("Unlimited new space size due to low promotion rate: %d
MB\n",
+ new_space_.MaximumCapacity() / MB);
+ }
+ }
+
size_of_old_gen_at_last_old_space_gc_ = PromotedSpaceSize();
if (high_survival_rate_during_scavenges &&
@@ -764,6 +791,11 @@ bool Heap::PerformGarbageCollection(GarbageCollector
collector,
UpdateSurvivalRateTrend(start_new_space_size);
}
+ if (new_space_high_promotion_mode_active_ &&
+ new_space_.Capacity() > new_space_.InitialCapacity()) {
+ new_space_.Shrink();
+ }
+
isolate_->counters()->objs_since_last_young()->Set(0);
gc_post_processing_depth_++;
@@ -916,9 +948,11 @@ static void VerifyNonPointerSpacePointers() {
void Heap::CheckNewSpaceExpansionCriteria() {
if (new_space_.Capacity() < new_space_.MaximumCapacity() &&
- survived_since_last_expansion_ > new_space_.Capacity()) {
- // Grow the size of new space if there is room to grow and enough
- // data has survived scavenge since the last expansion.
+ survived_since_last_expansion_ > new_space_.Capacity() &&
+ !new_space_high_promotion_mode_active_) {
+ // Grow the size of new space if there is room to grow, enough data
+ // has survived scavenge since the last expansion and we are not in
+ // high promotion mode.
new_space_.Grow();
survived_since_last_expansion_ = 0;
}
Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index
9f4f505e1d9d04a6695b1cd2d92a776e982263d0..081c4663de49df6b48ab7c3a251c29c24409d0d0
100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -1569,6 +1569,10 @@ class Heap {
HeapDebugUtils* debug_utils_;
#endif // DEBUG
+ // Indicates that the new space should be kept small due to high
promotion
+ // rates caused by the mutator allocating a lot of long-lived objects.
+ bool new_space_high_promotion_mode_active_;
+
// Limit that triggers a global GC on the next (normally caused) GC.
This
// is checked when we have already decided to do a GC to help determine
// which collector to invoke.
@@ -1809,6 +1813,10 @@ class Heap {
return survival_rate_trend() == INCREASING;
}
+ bool IsDecreasingSurvivalTrend() {
+ return survival_rate_trend() == DECREASING;
+ }
+
bool IsHighSurvivalRate() {
return high_survival_rate_period_length_ > 0;
}
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