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Code cache should be explicit about what it caches
https://bugs.webkit.org/show_bug.cgi?id=110039 Reviewed by Oliver Hunt. This patch makes the code cache more explicit in two ways: (1) The cache caches top-level scripts. Any sub-functions executed as a part of a script are cached with it and evicted with it. This simplifies things by eliminating out-of-band sub-function tracking, and fixes pathological cases where functions for live scripts would be evicted in favor of functions for dead scripts, and/or high probability functions executed early in script lifetime would be evicted in favor of low probability functions executed late in script lifetime, due to LRU. Statistical data from general browsing and PLT confirms that caching functions independently of scripts is not profitable. (2) The cache tracks script size, not script count. This reduces the worst-case cache size by a factor of infinity. Script size is a reasonable first-order estimate of in-memory footprint for a cached script because there are no syntactic constructs that have super-linear memory footprint. * bytecode/UnlinkedCodeBlock.cpp: (JSC::generateFunctionCodeBlock): Moved this function out of the cache because it does not consult the cache, and is not managed by it. (JSC::UnlinkedFunctionExecutable::visitChildren): Visit our code blocks because they are strong references now, rather than weak, a la (1). (JSC::UnlinkedFunctionExecutable::codeBlockFor): Updated for interface changes. * bytecode/UnlinkedCodeBlock.h: (UnlinkedFunctionExecutable): (UnlinkedFunctionCodeBlock): Strong now, not weak, a la (1). * runtime/CodeCache.cpp: (JSC::CodeCache::CodeCache): * runtime/CodeCache.h: (JSC::SourceCodeKey::length): (SourceCodeKey): (CodeCacheMap): (JSC::CodeCacheMap::CodeCacheMap): (JSC::CodeCacheMap::find): (JSC::CodeCacheMap::set): (JSC::CodeCacheMap::clear): (CodeCache): (JSC::CodeCache::clear): Removed individual function tracking, due to (1). Added explicit character counting, for (2). You might think 16000000 characters is a lot. It is. But this patch didn't establish that limit -- it just took the existing limit and made it more visible. I intend to reduce the size of the cache in a future patch. Canonical link: https://commits.webkit.org/128334@main git-svn-id: https://svn.webkit.org/repository/webkit/trunk@143133 268f45cc-cd09-0410-ab3c-d52691b4dbfc
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