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[feedback] Only take read lock for data pairs on the background thread

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Slight performance regression by adding locking around feedback
vector get/set. The lock isn't necessary for reads on the main thread,
since the main thread is the only source of change.

Bug: chromium:1144777
Change-Id: I7cc9898ad0d8e8c468ba150c0bc6bef3176fd256
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2516475
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70947}
This commit is contained in:
Mike Stanton 2020-11-03 13:08:55 +01:00 committed by Commit Bot
parent 70a1de97c6
commit 8574179a90
1 changed files with 8 additions and 3 deletions
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11
src/objects/feedback-vector.cc
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@ -500,11 +500,16 @@ void NexusConfig::SetFeedbackPair(FeedbackVector vector,
std::pair<MaybeObject, MaybeObject> NexusConfig::GetFeedbackPair(
FeedbackVector vector, FeedbackSlot slot) const {
base::SharedMutexGuard<base::kShared> shared_mutex_guard(
isolate()->feedback_vector_access());
if (mode() == BackgroundThread) {
isolate()->feedback_vector_access()->LockShared();
}
MaybeObject feedback = vector.Get(slot);
MaybeObject feedback_extra = vector.Get(slot.WithOffset(1));
return std::make_pair(feedback, feedback_extra);
auto return_value = std::make_pair(feedback, feedback_extra);
if (mode() == BackgroundThread) {
isolate()->feedback_vector_access()->UnlockShared();
}
return return_value;
}
FeedbackNexus::FeedbackNexus(Handle<FeedbackVector> vector, FeedbackSlot slot)