Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 128591e637758eb30386fdad64d648ee08535581
https://github.com/WebKit/WebKit/commit/128591e637758eb30386fdad64d648ee08535581
Author: Sosuke Suzuki <[email protected]>
Date: 2026-04-16 (Thu, 16 Apr 2026)
Changed paths:
A JSTests/microbenchmarks/json-parse-repeated-short-strings.js
A JSTests/stress/json-parse-jsstring-cache-coherence.js
M Source/JavaScriptCore/heap/Heap.cpp
M Source/JavaScriptCore/runtime/JSONAtomStringCache.h
M Source/JavaScriptCore/runtime/JSONAtomStringCacheInlines.h
M Source/JavaScriptCore/runtime/LiteralParser.cpp
Log Message:
-----------
[JSC] Cache `JSString` cells for short `JSON.parse` string values
https://bugs.webkit.org/show_bug.cgi?id=312224
Reviewed by Yusuke Suzuki.
JSONAtomStringCache caches AtomStringImpl for object keys, but string
*values* still allocated a fresh JSString cell on every occurrence via
jsString(), even for repeated short strings like "type":"text" or
enum-style arrays.
Add a parallel std::array<JSString*, 256> m_jsStrings keyed by the same
slot index. makeJSString() returns the cached cell on a buffer hit;
makeIdentifier() nulls the parallel entry on slot eviction to keep them
coherent. The array is cleared in Heap::finalize() alongside the other
raw-pointer string caches, so no visiting is needed.
The cache range stays at len<=10 to avoid AtomString table churn on
payloads with many unique medium-length values (todomvc-style).
TipOfTree Patched
json-parse-repeated-short-strings 25.6922+-0.1853 ^
17.1671+-0.4399 ^ definitely 1.4966x faster
* JSTests/microbenchmarks/json-parse-repeated-short-strings.js: Added.
* JSTests/stress/json-parse-jsstring-cache-coherence.js: Added.
* Source/JavaScriptCore/heap/Heap.cpp:
(JSC::Heap::finalize): Clear m_jsStrings on every collection.
* Source/JavaScriptCore/runtime/JSONAtomStringCache.h:
Add m_jsStrings parallel array, cacheIndex() helper, clearJSStrings().
* Source/JavaScriptCore/runtime/JSONAtomStringCacheInlines.h:
(JSC::JSONAtomStringCache::makeIdentifier): Null m_jsStrings[index] on
slot eviction.
(JSC::JSONAtomStringCache::makeJSString): Added.
* Source/JavaScriptCore/runtime/LiteralParser.cpp:
(JSC::LiteralParser::makeJSString): Delegate to the new cache API.
Canonical link: https://commits.webkit.org/311426@main
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