is much slower in FF than Chrome




7 years ago
4 years ago


(Reporter: jrmuizel, Unassigned)


Firefox Tracking Flags

(Not tracked)




7 years ago
I haven't profiled it yet, but my guess is that it's JS

Comment 1

7 years ago
The source for the slow one is at:

The hottest pieces are:
531.0ms    3.4%	 	js::mjit::stubs::FixupArity(js::VMFrame&, unsigned int)
424.0ms    2.7%	 	CallCompiler::generateNativeStub()
396.0ms    2.5%	 	bool js::gc::Arena::finalize<JSObject>(JSContext*, js::gc::AllocKind, unsigned long)
Assuming I did the git magic right to check out the right thing....

Looks like 42% of the time is methodjit generated code, 7% is under array_slice, another 5% doing generateNativeStub stuff around the array_slice.  This is all under the NativeCall ic.

8% under array_extra, half of this calling back into JS.  5% allocating arrays directly from jitcode.  Lots of stubcalls (FixupArity, CreateThis, GetElem, StrictEq, Arguments, FlatLambda).

2% actual mjit compilation via TryCompile.

All those percentages are of total time, not main thread time.  Main thread is about 92% of total; the remainder looks like the GC finalization thread, almost all self time in FinalizeArenas.


4 years ago
Assignee: general → nobody
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