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[bmalloc] Use madvise(MADV_ZERO) instead of mmap to zero memory #47308

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Merged
merged 1 commit into from
Jun 28, 2025
Merged

[bmalloc] Use madvise(MADV_ZERO) instead of mmap to zero memory #47308

merged 1 commit into from
Jun 28, 2025
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Achierius
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@Achierius Achierius commented Jun 27, 2025 •
edited by webkit-early-warning-system
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1747d6d

[bmalloc] Use madvise(MADV_ZERO) instead of mmap to zero memory
https://bugs.webkit.org/show_bug.cgi?id=295104
rdar://154496366

Reviewed by Yusuke Suzuki.

Using mmap is pessimizing; I previously fixed this for libpas,
but I didn't realize at the time that there's a parallel flow
in bmalloc. This change thus corresponds to 296321@main, which
solves the same issue but for libpas.

* Source/bmalloc/bmalloc.xcodeproj/project.pbxproj:
* Source/bmalloc/bmalloc/VMAllocate.cpp: Added.
(bmalloc::zeroFillLatchIfMadvZeroIsSupported):
(bmalloc::isMadvZeroSupported):
* Source/bmalloc/bmalloc/VMAllocate.h:
(bmalloc::vmZeroAndPurge):

Canonical link: https://commits.webkit.org/296771@main

8a9b018

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❌ 🧪 style ✅ 🛠 ios ✅ 🛠 mac ✅ 🛠 wpe ✅ 🛠 win
✅ 🛠 ios-sim ✅ 🛠 mac-AS-debug ✅ 🧪 wpe-wk2 ⏳ 🧪 win-tests
✅ 🧪 webkitperl ✅ 🧪 ios-wk2 ✅ 🧪 api-mac ✅ 🧪 api-wpe
✅ 🧪 ios-wk2-wpt ✅ 🧪 mac-wk1 ✅ 🛠 wpe-cairo
✅ 🛠 🧪 jsc ✅ 🧪 api-ios ✅ 🧪 mac-wk2 ✅ 🛠 gtk
✅ 🛠 🧪 jsc-arm64 ✅ 🛠 vision ✅ 🧪 mac-AS-debug-wk2 ✅ 🧪 gtk-wk2
✅ 🛠 vision-sim ✅ 🧪 mac-wk2-stress ✅ 🧪 api-gtk
  🛠 🧪 merge ✅ 🧪 vision-wk2 ✅ 🧪 mac-intel-wk2 ✅ 🛠 playstation
✅ 🛠 🧪 unsafe-merge ✅ 🛠 tv ✅ 🛠 jsc-armv7
✅ 🛠 tv-sim ✅ 🧪 jsc-armv7-tests
✅ 🛠 watch
✅ 🛠 watch-sim

@Achierius Achierius requested a review from a team as a code owner June 27, 2025 17:32
@Achierius Achierius self-assigned this Jun 27, 2025
@Achierius Achierius added the bmalloc For bugs in bmalloc label Jun 27, 2025
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webkit-early-warning-system commented Jun 27, 2025 •
edited
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EWS run on current version of this PR (hash 8a9b018)

Misc iOS, visionOS, tvOS & watchOS macOS Linux Windows
❌ 🧪 style ✅ 🛠 ios ✅ 🛠 mac ✅ 🛠 wpe ✅ 🛠 win
✅ 🛠 ios-sim ✅ 🛠 mac-AS-debug ✅ 🧪 wpe-wk2 ⏳ 🧪 win-tests
✅ 🧪 webkitperl ✅ 🧪 ios-wk2 ✅ 🧪 api-mac ✅ 🧪 api-wpe
✅ 🧪 ios-wk2-wpt ✅ 🧪 mac-wk1 ✅ 🛠 wpe-cairo
✅ 🛠 🧪 jsc ✅ 🧪 api-ios ✅ 🧪 mac-wk2 ✅ 🛠 gtk
✅ 🛠 🧪 jsc-arm64 ✅ 🛠 vision ✅ 🧪 mac-AS-debug-wk2 ✅ 🧪 gtk-wk2
✅ 🛠 vision-sim ✅ 🧪 mac-wk2-stress ✅ 🧪 api-gtk
  🛠 🧪 merge ✅ 🧪 vision-wk2 ✅ 🧪 mac-intel-wk2 ✅ 🛠 playstation
✅ 🛠 🧪 unsafe-merge ✅ 🛠 tv ✅ 🛠 jsc-armv7
✅ 🛠 tv-sim ✅ 🧪 jsc-armv7-tests
✅ 🛠 watch
✅ 🛠 watch-sim

@Achierius Achierius added unsafe-merge-queue Applied to send a pull request to merge-queue, but skip building and testing merge-queue Applied to send a pull request to merge-queue and removed unsafe-merge-queue Applied to send a pull request to merge-queue, but skip building and testing labels Jun 28, 2025
@Achierius
[bmalloc] Use madvise(MADV_ZERO) instead of mmap to zero memory
1747d6d 
https://bugs.webkit.org/show_bug.cgi?id=295104
rdar://154496366

Reviewed by Yusuke Suzuki.

Using mmap is pessimizing; I previously fixed this for libpas,
but I didn't realize at the time that there's a parallel flow
in bmalloc. This change thus corresponds to 296321@main, which
solves the same issue but for libpas.

* Source/bmalloc/bmalloc.xcodeproj/project.pbxproj:
* Source/bmalloc/bmalloc/VMAllocate.cpp: Added.
(bmalloc::zeroFillLatchIfMadvZeroIsSupported):
(bmalloc::isMadvZeroSupported):
* Source/bmalloc/bmalloc/VMAllocate.h:
(bmalloc::vmZeroAndPurge):

Canonical link: https://commits.webkit.org/296771@main
@webkit-commit-queue webkit-commit-queue force-pushed the eng/bmalloc-use-MADV_ZERO branch from 8a9b018 to 1747d6d Compare June 28, 2025 17:04
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Committed 296771@main (1747d6d): https://commits.webkit.org/296771@main

Reviewed commits have been landed. Closing PR #47308 and removing active labels.

@webkit-commit-queue webkit-commit-queue merged commit 1747d6d into WebKit:main Jun 28, 2025
@webkit-commit-queue webkit-commit-queue removed the merge-queue Applied to send a pull request to merge-queue label Jun 28, 2025
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