Reland "[zone] Keep one page when we Zone::Reset for reuse"

This is a reland of 2418d22a37

Reland fixes:
  * Rebase this 2+ year old change 😱
  * Unpoison the kept segment before zapping it to make ASAN happy.
  * Carefully adjust allocation size tracking fields to compensate for
    kept segment.

Original change's description:
> [zone] Keep one page when we Zone::Reset for reuse
>
> Change-Id: I50c6124d3da5b35d4156c066f38d10d2dc966567
> Reviewed-on: https://chromium-review.googlesource.com/c/1349246
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Commit-Queue: Toon Verwaest <verwaest@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#57793}

Change-Id: Iaffde5b38b3d683af081b1878464dd4c66be5af8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3322833
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78348}
This commit is contained in:
Leszek Swirski 2021-12-10 16:25:25 +01:00 committed by V8 LUCI CQ
parent 3312b952d1
commit 41b174a7f0
4 changed files with 28 additions and 6 deletions

View File

@ -1631,7 +1631,7 @@ void DeclarationScope::ResetAfterPreparsing(AstValueFactory* ast_value_factory,
// Get the zone, while variables_ is still valid
Zone* zone = this->zone();
variables_.Invalidate();
zone->ReleaseMemory();
zone->Reset();
}
if (aborted) {

View File

@ -197,7 +197,7 @@ class V8_EXPORT_PRIVATE ReusableUnoptimizedCompileState {
// Zone pointer in the AstValueFactory.
Zone* single_parse_zone() { return &single_parse_zone_; }
void NotifySingleParseCompleted() { single_parse_zone_.ReleaseMemory(); }
void NotifySingleParseCompleted() { single_parse_zone_.Reset(); }
AstValueFactory* ast_value_factory() const {
return ast_value_factory_.get();

View File

@ -70,9 +70,30 @@ void* Zone::AsanNew(size_t size) {
return reinterpret_cast<void*>(result);
}
void Zone::ReleaseMemory() {
void Zone::Reset() {
if (!segment_head_) return;
Segment* keep = segment_head_;
segment_head_ = segment_head_->next();
if (segment_head_ != nullptr) {
// Reset the position to the end of the new head, and uncommit its
// allocation size (which will be re-committed in DeleteAll).
position_ = segment_head_->end();
allocation_size_ -= segment_head_->end() - segment_head_->start();
}
keep->set_next(nullptr);
DeleteAll();
allocator_->TraceZoneCreation(this);
// Un-poison the kept segment content so we can zap and re-use it.
ASAN_UNPOISON_MEMORY_REGION(reinterpret_cast<void*>(keep->start()),
keep->capacity());
keep->ZapContents();
segment_head_ = keep;
position_ = keep->start();
limit_ = keep->end();
DCHECK_EQ(allocation_size(), 0);
DCHECK_EQ(segment_bytes_allocated_, keep->total_size());
}
void Zone::DeleteAll() {

View File

@ -134,9 +134,10 @@ class V8_EXPORT_PRIVATE Zone final {
// Seals the zone to prevent any further allocation.
void Seal() { sealed_ = true; }
// Allows the zone to be safely reused. Releases the memory and fires zone
// destruction and creation events for the accounting allocator.
void ReleaseMemory();
// Allows the zone to be safely reused. Releases the memory except for the
// last page, and fires zone destruction and creation events for the
// accounting allocator.
void Reset();
// Returns true if more memory has been allocated in zones than
// the limit allows.