Using tooling from bug 186698, loading can and running "notifyutil -p com.apple.WebKit.dumpHashTableCapacity" shows: Wasted capacity: 205296 bytes (used 84624 of 289920 bytes, utilization: 29.19%) - 727 allocations 1 0x116681ba5 WTF::HashTable<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, WTF::KeyValuePair<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Weak<JSC::Structure> >, WTF::KeyValuePairKeyExtractor<WTF::KeyValuePair<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Weak<JSC::Structure> > >, JSC::StructureTransitionTable::Hash, WTF::HashMap<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Weak<JSC::Structure>, JSC::StructureTransitionTable::Hash, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> >, WTF::HashTraits<JSC::Weak<JSC::Structure> > >::KeyValuePairTraits, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> > >::HashTable() 2 0x116681b85 WTF::HashMap<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Weak<JSC::Structure>, JSC::StructureTransitionTable::Hash, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> >, WTF::HashTraits<JSC::Weak<JSC::Structure> > >::HashMap() 3 0x116681ae5 WTF::HashMap<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Weak<JSC::Structure>, JSC::StructureTransitionTable::Hash, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> >, WTF::HashTraits<JSC::Weak<JSC::Structure> > >::HashMap() 4 0x116681a9b JSC::WeakGCMap<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Structure, JSC::StructureTransitionTable::Hash, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> > >::WeakGCMap(JSC::VM&) 5 0x1166706fd JSC::WeakGCMap<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Structure, JSC::StructureTransitionTable::Hash, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> > >::WeakGCMap(JSC::VM&) 6 0x116670392 JSC::StructureTransitionTable::add(JSC::VM&, JSC::Structure*) 7 0x11667357f JSC::Structure::addNewPropertyTransition(JSC::VM&, JSC::Structure*, JSC::PropertyName, unsigned int, int&, JSC::PutPropertySlot::Context, JSC::DeferredStructureTransitionWatchpointFire*) 8 0x115bf8787 bool JSC::JSObject::putDirectInternal<(JSC::JSObject::PutMode)0>(JSC::VM&, JSC::PropertyName, JSC::JSValue, unsigned int, JSC::PutPropertySlot&)
<rdar://problem/41189112>
On nytimes.com: Wasted capacity: 124056 bytes (used 63720 of 187776 bytes, utilization: 33.93%) - 289 allocations 1 0x116681ba5 WTF::HashTable<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, WTF::KeyValuePair<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Weak<JSC::Structure> >, WTF::KeyValuePairKeyExtractor<WTF::KeyValuePair<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Weak<JSC::Structure> > >, JSC::StructureTransitionTable::Hash, WTF::HashMap<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Weak<JSC::Structure>, JSC::StructureTransitionTable::Hash, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> >, WTF::HashTraits<JSC::Weak<JSC::Structure> > >::KeyValuePairTraits, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> > >::HashTable() 2 0x116681b85 WTF::HashMap<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Weak<JSC::Structure>, JSC::StructureTransitionTable::Hash, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> >, WTF::HashTraits<JSC::Weak<JSC::Structure> > >::HashMap() 3 0x116681ae5 WTF::HashMap<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Weak<JSC::Structure>, JSC::StructureTransitionTable::Hash, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> >, WTF::HashTraits<JSC::Weak<JSC::Structure> > >::HashMap() 4 0x116681a9b JSC::WeakGCMap<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Structure, JSC::StructureTransitionTable::Hash, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> > >::WeakGCMap(JSC::VM&) 5 0x1166706fd JSC::WeakGCMap<std::__1::pair<WTF::UniquedStringImpl*, unsigned int>, JSC::Structure, JSC::StructureTransitionTable::Hash, WTF::HashTraits<std::__1::pair<WTF::UniquedStringImpl*, unsigned int> > >::WeakGCMap(JSC::VM&) 6 0x116670392 JSC::StructureTransitionTable::add(JSC::VM&, JSC::Structure*) 7 0x11667357f JSC::Structure::addNewPropertyTransition(JSC::VM&, JSC::Structure*, JSC::PropertyName, unsigned int, int&, JSC::PutPropertySlot::Context, JSC::DeferredStructureTransitionWatchpointFire*) 8 0x11536ad9c bool JSC::JSObject::putDirectInternal<(JSC::JSObject::PutMode)1>(JSC::VM&, JSC::PropertyName, JSC::JSValue, unsigned int, JSC::PutPropertySlot&)