Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: e498e0debab264e2d840a9e74613b60c420d04f4
https://github.com/WebKit/WebKit/commit/e498e0debab264e2d840a9e74613b60c420d04f4
Author: Yusuke Suzuki <[email protected]>
Date: 2025-06-30 (Mon, 30 Jun 2025)
Changed paths:
M Source/JavaScriptCore/heap/MarkedBlock.cpp
M Source/JavaScriptCore/heap/MarkedBlock.h
M Source/JavaScriptCore/heap/MarkedBlockInlines.h
M Source/JavaScriptCore/runtime/OptionsList.h
Log Message:
-----------
[JSC] Use BitSet for MarkedBlock::sweep
https://bugs.webkit.org/show_bug.cgi?id=295083
rdar://154457450
Reviewed by Yijia Huang.
This patch changes MarkedBlock::sweep by using BitSet.
1. Instead of iterating each cell, this patch uses BitSet.
We construct these set from m_marks and m_newlyAllocated.
These BitSet will answer liveness information super quickly,
and iterating these bits are very efficient, in particular
given that BitSet is already sparse (since atom size is smaller
than cell size in most cases).
2. We copy BitSet before iterating them. So we can get snapshot of
liveness information. We no longer need to push cells to the
Vector for concurrent marking case since this liveness information
is enough.
3. We construct FreeList in a forward direction. And we also call
scribble / destructor too. So we can keep touching the same region
well. Furthermore, we can do destroy calls in a bulk manner.
4. We leverage "unswept" bit and avoid calling destructors when unswept
bit was not set. This happens when we call resumeAllocation
(reconstructing FreeList to resume peripheral threads). In this case,
we do not need to call destructors since our liveness condition is
not changed from the previous sweeping, otherwise, unswept bit is
updated.
5. We also remove useBumpAllocator option. Now we are always using
interval based FreeList. So this option is meaningless.
* Source/JavaScriptCore/heap/MarkedBlock.cpp:
(JSC::MarkedBlock::Handle::sweep):
* Source/JavaScriptCore/heap/MarkedBlock.h:
* Source/JavaScriptCore/heap/MarkedBlockInlines.h:
(JSC::MarkedBlock::Handle::specializedSweep):
(JSC::MarkedBlock::Handle::sweepDestructionMode):
(JSC::DeadCellStorage::append): Deleted.
(): Deleted.
* Source/JavaScriptCore/runtime/OptionsList.h:
Canonical link: https://commits.webkit.org/296816@main
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