Bug 75569 – DOM Attribute tests on Dromaeo spends 2.7% of time in hasSelectorForAttribute

• Status: RESOLVED
• Resolution: FIXED
• Component: DOM

[Ryosuke Niwa]

Go to http://dromaeo.com/?dom and profiled WebKit r103959 while it was running DOM Attributes tests.

Besides AtomicString::addSlowCase which accounts for about 12% of time, we spend 2.7% of time in hasSelectorForAttribute. We can probably use bloom filter there as anttik suggested.

	6.6%	6.6%	JavaScriptCore	JSC::IdentifierTable::add(WTF::StringImpl*)
	5.8%	5.8%	JavaScriptCore	WTF::AtomicString::addSlowCase(WTF::StringImpl*)
	5.1%	5.1%	WebCore	WTF::HashTableIterator<WTF::StringImpl*, std::pair<WTF::StringImpl*, JSC::Weak<JSC::JSString> >, WTF::PairFirstExtractor<std::pair<WTF::StringImpl*, JSC::Weak<JSC::JSString> > >, WTF::StringHash, WTF::PairHashTraits<WTF::HashTraits<WTF::StringImpl*>, WTF::HashTraits<JSC::Weak<JSC::JSString> > >, WTF::HashTraits<WTF::StringImpl*> > WTF::HashTable<WTF::StringImpl*, std::pair<WTF::StringImpl*, JSC::Weak<JSC::JSString> >, WTF::PairFirstExtractor<std::pair<WTF::StringImpl*, JSC::Weak<JSC::JSString> > >, WTF::StringHash, WTF::PairHashTraits<WTF::HashTraits<WTF::StringImpl*>, WTF::HashTraits<JSC::Weak<JSC::JSString> > >, WTF::HashTraits<WTF::StringImpl*> >::find<WTF::IdentityHashTranslator<WTF::StringHash>, WTF::StringImpl*>(WTF::StringImpl* const&)
	0.0%	5.0%	WebCore	 WebCore::jsString(JSC::ExecState*, WTF::String const&)
	0.0%	0.1%	WebCore	 WebCore::jsHTMLElementId(JSC::ExecState*, JSC::JSValue, JSC::Identifier const&)
	0.0%	0.0%	WebCore	 WebCore::jsStringOrNull(JSC::ExecState*, WTF::String const&)
	3.5%	3.5%	WebCore	WebCore::JSHTMLElement::getOwnPropertySlot(JSC::JSCell*, JSC::ExecState*, JSC::Identifier const&, JSC::PropertySlot&)
	3.5%	3.5%	JavaScriptCore	JSC::MarkedBlock::sweep(JSC::MarkedBlock::SweepMode)
	3.1%	3.1%	Unknown Library	0x2becb9401640 [23.2KB]
	2.9%	2.9%	JavaScriptCore	JSC::JSValue::toPrimitiveString(JSC::ExecState*) const
	2.7%	2.7%	WebCore	bool WTF::HashTable<WTF::AtomicStringImpl*, WTF::AtomicStringImpl*, WTF::IdentityExtractor, WTF::PtrHash<WTF::AtomicStringImpl*>, WTF::HashTraits<WTF::AtomicStringImpl*>, WTF::HashTraits<WTF::AtomicStringImpl*> >::contains<WTF::IdentityHashTranslator<WTF::PtrHash<WTF::AtomicStringImpl*> >, WTF::AtomicStringImpl*>(WTF::AtomicStringImpl* const&) const
	0.0%	2.7%	WebCore	 WebCore::CSSStyleSelector::hasSelectorForAttribute(WTF::AtomicString const&) const
	0.0%	2.7%	WebCore	  WebCore::Element::recalcStyleIfNeededAfterAttributeChanged(WebCore::Attribute*)
	0.0%	2.7%	WebCore	   WebCore::StyledElement::attributeChanged(WebCore::Attribute*, bool)
	0.0%	2.7%	WebCore	    WebCore::Element::didModifyAttribute(WebCore::Attribute*)
	0.0%	1.8%	WebCore	     WebCore::Element::setAttribute(WebCore::QualifiedName const&, WTF::AtomicString const&)
	0.0%	1.0%	WebCore	     WebCore::Element::setAttribute(WTF::AtomicString const&, WTF::AtomicString const&, int&)
	0.0%	0.0%	WebCore	 WebCore::Element::recalcStyleIfNeededAfterAttributeChanged(WebCore::Attribute*)

[Ryosuke Niwa]

It seems like just checking needsStyleRecalc() first suffice to improve the performance here.

After adding the check, we get:

	6.1%	6.1%	JavaScriptCore	JSC::IdentifierTable::add(WTF::StringImpl*)
	5.4%	5.4%	JavaScriptCore	WTF::AtomicString::addSlowCase(WTF::StringImpl*)
	4.7%	4.7%	WebCore	WTF::HashTableIterator<WTF::StringImpl*, std::pair<WTF::StringImpl*, JSC::Weak<JSC::JSString> >, WTF::PairFirstExtractor<std::pair<WTF::StringImpl*, JSC::Weak<JSC::JSString> > >, WTF::StringHash, WTF::PairHashTraits<WTF::HashTraits<WTF::StringImpl*>, WTF::HashTraits<JSC::Weak<JSC::JSString> > >, WTF::HashTraits<WTF::StringImpl*> > WTF::HashTable<WTF::StringImpl*, std::pair<WTF::StringImpl*, JSC::Weak<JSC::JSString> >, WTF::PairFirstExtractor<std::pair<WTF::StringImpl*, JSC::Weak<JSC::JSString> > >, WTF::StringHash, WTF::PairHashTraits<WTF::HashTraits<WTF::StringImpl*>, WTF::HashTraits<JSC::Weak<JSC::JSString> > >, WTF::HashTraits<WTF::StringImpl*> >::find<WTF::IdentityHashTranslator<WTF::StringHash>, WTF::StringImpl*>(WTF::StringImpl* const&)
	3.6%	3.6%	Unknown Library	0x5c76577ee160 [11.3KB]
	3.1%	3.1%	WebCore	WebCore::JSHTMLElement::getOwnPropertySlot(JSC::JSCell*, JSC::ExecState*, JSC::Identifier const&, JSC::PropertySlot&)
	3.1%	3.1%	JavaScriptCore	JSC::MarkedBlock::sweep(JSC::MarkedBlock::SweepMode)
	3.0%	3.0%	WebCore	WebCore::jsString(JSC::ExecState*, WTF::String const&)
	2.9%	2.9%	WebCore	WebCore::Element::setAttribute(WTF::AtomicString const&, WTF::AtomicString const&, int&)
	2.9%	2.9%	JavaScriptCore	JSC::JSValue::toPrimitiveString(JSC::ExecState*) const
	2.7%	2.7%	WebCore	WebCore::JSHTMLHeadingElement::getOwnPropertySlot(JSC::JSCell*, JSC::ExecState*, JSC::Identifier const&, JSC::PropertySlot&)
	2.7%	2.7%	WebCore	JSC::JSValue::toString(JSC::ExecState*) const
	2.7%	2.7%	JavaScriptCore	JSC::JSString::resolveRope(JSC::ExecState*) const
	2.6%	2.6%	JavaScriptCore	JSC::JSValue::get(JSC::ExecState*, JSC::Identifier const&, JSC::PropertySlot&) const
	2.4%	2.4%	Unknown Library	0x5c76577b2980 [5.3KB]
	2.4%	2.4%	WebCore	WebCore::Element::idAttributeChanged(WebCore::Attribute*)
	2.3%	2.3%	JavaScriptCore	WTF::StringImpl::lower()
	2.2%	2.2%	WebCore	WebCore::Element::getAttribute(WebCore::QualifiedName const&) const
	2.2%	2.2%	WebCore	WebCore::jsElementPrototypeFunctionSetAttribute(JSC::ExecState*)
	2.0%	2.0%	JavaScriptCore	WTF::AtomicString::lower() const
	1.9%	1.9%	WebCore	WebCore::jsElementPrototypeFunctionGetAttribute(JSC::ExecState*)
	1.9%	1.9%	WebCore	WebCore::StyledElement::attributeChanged(WebCore::Attribute*, bool)
	1.8%	1.8%	JavaScriptCore	JSC::JSString::destroy(JSC::JSCell*)
	1.7%	1.7%	JavaScriptCore	WTF::tryFastMalloc(unsigned long)
	1.7%	1.7%	WebCore	WebCore::Element::setAttribute(WebCore::QualifiedName const&, WTF::AtomicString const&)
	1.6%	1.6%	WebCore	WebCore::JSHTMLAnchorElement::put(JSC::JSCell*, JSC::ExecState*, JSC::Identifier const&, JSC::JSValue, JSC::PutPropertySlot&)
	1.3%	1.3%	Unknown Library	0x5c7657646900 [5.4KB]
	1.3%	1.3%	JavaScriptCore	JSC::JSObject::put(JSC::JSCell*, JSC::ExecState*, JSC::Identifier const&, JSC::JSValue, JSC::PutPropertySlot&)
	1.2%	1.2%	WebCore	WebCore::JSHTMLElement::put(JSC::JSCell*, JSC::ExecState*, JSC::Identifier const&, JSC::JSValue, JSC::PutPropertySlot&)
	1.2%	1.2%	WebCore	WebCore::HTMLAnchorElement::parseMappedAttribute(WebCore::Attribute*)
	1.0%	1.0%	JavaScriptCore	operationGetByVal
	1.0%	1.0%	Unknown Library	0x5c765761a200 [1.9KB]
	1.0%	1.0%	JavaScriptCore	cti_op_put_by_val

[Ryosuke Niwa]

Created attachment 121215 [details]
Checks needsStyleRecalc() first

[Andreas Kling]

Comment on attachment 121215 [details]
Checks needsStyleRecalc() first

Nice!

[WebKit Review Bot]

Comment on attachment 121215 [details]
Checks needsStyleRecalc() first

Clearing flags on attachment: 121215

Committed r104165: <http://trac.webkit.org/changeset/104165>

[WebKit Review Bot]

All reviewed patches have been landed.  Closing bug.

[Antti Koivisto]

How much did this patch actually improve the performance?

[Ryosuke Niwa]

It appears that there's some statistically significant improvement.

with patch:
537.46 runs/s
539.04 runs/s
523.74 runs/s
533.79 runs/s
544.72 runs/s
541.45 runs/s
518.91 runs/s
avg: 534.16
stdev: 9.49 (1.78%)

without patch:
529.29 runs/s
517.19 runs/s
512.61 runs/s
515.45 runs/s
529.42 runs/s
517.45 runs/s
508.90 runs/s
avg: 518.62
stdev: 2.90 (1.52%)

Improvement: 2.91%

[Ryosuke Niwa]

The scores were measured on r103634 (Apple's mac port); btw, the measured performance gain appears to match the profiling result so we've basically eliminated the time spent inside hasSelectorForAttribute :D.