Bug 186729

Summary: StructureCache wastes 240KB of HashTable capacity on cnn.com
Product: WebKit Reporter: Simon Fraser (smfr) <simon.fraser>
Component: JavaScriptCoreAssignee: Nobody <webkit-unassigned>
Status: NEW ---    
Severity: Normal CC: keith_miller, saam, simon.fraser, webkit-bug-importer, ysuzuki
Priority: P2 Keywords: InRadar
Version: WebKit Nightly Build   
Hardware: Unspecified   
OS: Unspecified   

Description Simon Fraser (smfr) 2018-06-16 12:24:55 PDT 
Using tooling from bug 186698, loading can and running "notifyutil -p com.apple.WebKit.dumpHashTableCapacity" shows:

Wasted capacity: 244368 bytes (used 148848 of 393216 bytes, utilization: 37.85%) - 1 allocations
1   0x1166cc265 WTF::HashTable<JSC::PrototypeKey, WTF::KeyValuePair<JSC::PrototypeKey, JSC::Weak<JSC::Structure> >, WTF::KeyValuePairKeyExtractor<WTF::KeyValuePair<JSC::PrototypeKey, JSC::Weak<JSC::Structure> > >, JSC::PrototypeKeyHash, WTF::HashMap<JSC::PrototypeKey, JSC::Weak<JSC::Structure>, JSC::PrototypeKeyHash, WTF::HashTraits<JSC::PrototypeKey>, WTF::HashTraits<JSC::Weak<JSC::Structure> > >::KeyValuePairTraits, WTF::HashTraits<JSC::PrototypeKey> >::HashTable()
2   0x1166cc245 WTF::HashMap<JSC::PrototypeKey, JSC::Weak<JSC::Structure>, JSC::PrototypeKeyHash, WTF::HashTraits<JSC::PrototypeKey>, WTF::HashTraits<JSC::Weak<JSC::Structure> > >::HashMap()
3   0x1166cc1a5 WTF::HashMap<JSC::PrototypeKey, JSC::Weak<JSC::Structure>, JSC::PrototypeKeyHash, WTF::HashTraits<JSC::PrototypeKey>, WTF::HashTraits<JSC::Weak<JSC::Structure> > >::HashMap()
4   0x1166cc15b JSC::WeakGCMap<JSC::PrototypeKey, JSC::Structure, JSC::PrototypeKeyHash, WTF::HashTraits<JSC::PrototypeKey> >::WeakGCMap(JSC::VM&)
5   0x1166cc10d JSC::WeakGCMap<JSC::PrototypeKey, JSC::Structure, JSC::PrototypeKeyHash, WTF::HashTraits<JSC::PrototypeKey> >::WeakGCMap(JSC::VM&)
6   0x1166cc0dd JSC::StructureCache::StructureCache(JSC::VM&)
7   0x1166bffed JSC::StructureCache::StructureCache(JSC::VM&)
8   0x1166bc42f JSC::VM::VM(JSC::VM::VMType, JSC::HeapType)
Comment 1 Radar WebKit Bug Importer 2018-06-16 12:25:20 PDT 
<rdar://problem/41189110>