Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: f0df03efe38c9dacfdb67ec002251ee110d7939f
      
https://github.com/WebKit/WebKit/commit/f0df03efe38c9dacfdb67ec002251ee110d7939f
  Author: Yusuke Suzuki <[email protected]>
  Date:   2026-07-03 (Fri, 03 Jul 2026)

  Changed paths:
    M Source/JavaScriptCore/assembler/CPU.cpp
    M Source/JavaScriptCore/assembler/CPU.h
    M Source/JavaScriptCore/runtime/Options.cpp

  Log Message:
  -----------
  [JSC] Tweak number of GC threads for Apple platforms
https://bugs.webkit.org/show_bug.cgi?id=318534
rdar://181304464

Reviewed by Tadeu Zagallo.

With our recent GC throughput optimizations etc.[1], GC scalability gets
improved and now we are seeing the best GC thread numbers are changed
from the previous static number "4" on Apple platforms. This patch
tweaks the heuristics based on P0 core and P1 core counts. The best
numbers are selected with A/B testing with various benchmarks on various
devices, and summarizing the characteristics and selecting the # of
threads based on that with the current JSC implementation. It is
possible that the number may be changed with the future JSC
development, so the formula and numbers are current snapshot.

[1]: https://commits.webkit.org/316327@main

* Source/JavaScriptCore/assembler/CPU.cpp:
(JSC::hwPerfLevelPhysicalCPUMax):
(JSC::hwNumberOfP0Cores):
(JSC::hwNumberOfP1Cores):
(JSC::hwNumberOfP2Cores):
* Source/JavaScriptCore/assembler/CPU.h:
* Source/JavaScriptCore/runtime/Options.cpp:
(JSC::overrideDefaults):

Canonical link: https://commits.webkit.org/316502@main



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