Remove SizeAndAlignment class in TZone code. #57649

MenloDorian · 2026-02-01T04:07:47Z

`24c117b`

Remove SizeAndAlignment class in TZone code.
https://bugs.webkit.org/show_bug.cgi?id=306717
rdar://169370644

Reviewed by Keith Miller.

The SizeAndAlignment logic belongs in TZoneSpecification which defines a TZone type's
sorting algorithm / criteria.  This refactoring paves the way to add alternate TZone
categories that use different sorting algorithms for heap selection.

Also added some debugging info (file and line number) to TZoneSpecification because
classname alone is insufficient as there can be many classes with the same name.
Also enhanced TZoneHeapManager::dumpRegisteredTypes(0 to also print the pid to
distinguish between processes.

No new tests because this is a refactoring patch.  There is no behavior change..

* Source/bmalloc/bmalloc/TZoneHeap.h:
(bmalloc::api::TZoneDescriptorHashTrait::hash):
(bmalloc::api::TZoneSpecification::sizeClass const):
(bmalloc::api::TZoneSpecification::encodeSize):
(bmalloc::api::TZoneSpecification::encodeAlignment):
(bmalloc::api::TZoneSpecification::encodeDescriptor):
(bmalloc::api::SizeAndAlignment::encode): Deleted.
(bmalloc::api::SizeAndAlignment::decodeSize): Deleted.
(bmalloc::api::SizeAndAlignment::decodeAlignment): Deleted.
* Source/bmalloc/bmalloc/TZoneHeapInlines.h:
* Source/bmalloc/bmalloc/TZoneHeapManager.cpp:
(bmalloc::api::TZoneDescriptorDecoder::TZoneDescriptorDecoder):
(bmalloc::api::TZoneDescriptorDecoder::value const):
(bmalloc::api::TZoneDescriptorDecoder::sizeClass const):
(bmalloc::api::TZoneDescriptorDecoder::alignment const):
(bmalloc::api::TZoneHeapManager::dumpRegisteredTypes):
(bmalloc::api::TZoneHeapManager::bucketCountForSizeClass):
(bmalloc::api::TZoneHeapManager::bucketForKey):
(bmalloc::api::TZoneHeapManager::populateGroupBuckets):
(bmalloc::api::TZoneHeapManager::heapRefForTZoneType):
(bmalloc::api::TZoneHeapManager::TZoneHeapManager::heapRefForTZoneTypeDifferentSize):
* Source/bmalloc/bmalloc/TZoneHeapManager.h:

Canonical link: https://commits.webkit.org/306630@main

4dd3d22

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

webkit-early-warning-system · 2026-02-01T04:07:54Z

EWS run on current version of this PR (hash 4dd3d22)

Details

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

MenloDorian · 2026-02-01T04:24:02Z

Source/bmalloc/bmalloc/TZoneHeap.h

-struct TZoneSpecification {
    HeapRef* addressOfHeapRef;
    unsigned size;
+    uint16_t alignment;


This does not increase the size of TZoneSpecification. There's an unused padding bytes here that I'm fitting this alignment field into. Having the alignment here makes it easier to get this value later rather than always having to decode it from the descriptor.

kmiller68

r=me with minor nit.

kmiller68 · 2026-02-02T16:15:41Z

Source/bmalloc/bmalloc/TZoneHeap.h

 #define BUSE_TZONE_SPEC_NAME_ARG 0
 #if BUSE_TZONE_SPEC_NAME_ARG
-#define TZONE_SPEC_NAME_ARG(x)  , x
+#define TZONE_SPEC_NAME_ARG(x)  x, __FILE__, __LINE__,


Nit: We should probably use std::source_location for new code.

I'll make this change in a follow up later. Gonna land this PR as is for now.

https://bugs.webkit.org/show_bug.cgi?id=306717 rdar://169370644 Reviewed by Keith Miller. The SizeAndAlignment logic belongs in TZoneSpecification which defines a TZone type's sorting algorithm / criteria. This refactoring paves the way to add alternate TZone categories that use different sorting algorithms for heap selection. Also added some debugging info (file and line number) to TZoneSpecification because classname alone is insufficient as there can be many classes with the same name. Also enhanced TZoneHeapManager::dumpRegisteredTypes(0 to also print the pid to distinguish between processes. No new tests because this is a refactoring patch. There is no behavior change.. * Source/bmalloc/bmalloc/TZoneHeap.h: (bmalloc::api::TZoneDescriptorHashTrait::hash): (bmalloc::api::TZoneSpecification::sizeClass const): (bmalloc::api::TZoneSpecification::encodeSize): (bmalloc::api::TZoneSpecification::encodeAlignment): (bmalloc::api::TZoneSpecification::encodeDescriptor): (bmalloc::api::SizeAndAlignment::encode): Deleted. (bmalloc::api::SizeAndAlignment::decodeSize): Deleted. (bmalloc::api::SizeAndAlignment::decodeAlignment): Deleted. * Source/bmalloc/bmalloc/TZoneHeapInlines.h: * Source/bmalloc/bmalloc/TZoneHeapManager.cpp: (bmalloc::api::TZoneDescriptorDecoder::TZoneDescriptorDecoder): (bmalloc::api::TZoneDescriptorDecoder::value const): (bmalloc::api::TZoneDescriptorDecoder::sizeClass const): (bmalloc::api::TZoneDescriptorDecoder::alignment const): (bmalloc::api::TZoneHeapManager::dumpRegisteredTypes): (bmalloc::api::TZoneHeapManager::bucketCountForSizeClass): (bmalloc::api::TZoneHeapManager::bucketForKey): (bmalloc::api::TZoneHeapManager::populateGroupBuckets): (bmalloc::api::TZoneHeapManager::heapRefForTZoneType): (bmalloc::api::TZoneHeapManager::TZoneHeapManager::heapRefForTZoneTypeDifferentSize): * Source/bmalloc/bmalloc/TZoneHeapManager.h: Canonical link: https://commits.webkit.org/306630@main

webkit-commit-queue · 2026-02-02T16:29:52Z

Committed 306630@main (24c117b): https://commits.webkit.org/306630@main

Reviewed commits have been landed. Closing PR #57649 and removing active labels.

MenloDorian requested a review from a team as a code owner February 1, 2026 04:07

MenloDorian self-assigned this Feb 1, 2026

MenloDorian added the JavaScriptCore For bugs in JavaScriptCore, the JS engine used by WebKit, other than kxmlcore issues. label Feb 1, 2026

MenloDorian commented Feb 1, 2026

View reviewed changes

webkit-ews-buildbot added the merging-blocked Applied to prevent a change from being merged label Feb 1, 2026

MenloDorian removed the merging-blocked Applied to prevent a change from being merged label Feb 1, 2026

kmiller68 approved these changes Feb 2, 2026

View reviewed changes

MenloDorian added the unsafe-merge-queue Applied to send a pull request to merge-queue, but skip building and testing label Feb 2, 2026

webkit-commit-queue force-pushed the eng/Remove-SizeAndAlignment-class-in-TZone-code branch from 4dd3d22 to 24c117b Compare February 2, 2026 16:29

webkit-commit-queue merged commit 24c117b into WebKit:main Feb 2, 2026

webkit-commit-queue removed the unsafe-merge-queue Applied to send a pull request to merge-queue, but skip building and testing label Feb 2, 2026

MenloDorian deleted the eng/Remove-SizeAndAlignment-class-in-TZone-code branch February 2, 2026 21:55

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Remove SizeAndAlignment class in TZone code. #57649

Remove SizeAndAlignment class in TZone code. #57649

MenloDorian commented Feb 1, 2026 •

edited by webkit-early-warning-system

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Remove SizeAndAlignment class in TZone code. #57649

Remove SizeAndAlignment class in TZone code. #57649

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MenloDorian commented Feb 1, 2026 •

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