625335 - Investigate if JSCompartment::finalizeObjectArenaList could be optimized

Status: RESOLVED DUPLICATE of bug 625250

(Core :: JavaScript Engine, defect)

Description

[Olli Pettay [:smaug][[e-mail]]]

I was doing some random Shark profiling on FOTN, and 
JSCompartment::finalizeObjectArenaLists showed up under js_GC, especially free in it.
Could we somehow make that free to be run asynchronously or in a separate thread?
Or could we reuse the memory? (I have no idea what finalizeObjectArenaLists is freeing)

Focused on js_GC:
	0.0%	100.0%	libmozjs.dylib	js_GC(JSContext*, JSCompartment*, JSGCInvocationKind)
	9.7%	80.2%	libmozjs.dylib	 JSCompartment::finalizeObjectArenaLists(JSContext*)
	6.2%	63.1%	libSystem.B.dylib	  free
	33.0%	45.1%	libSystem.B.dylib	   szone_free
	7.7%	7.7%	libSystem.B.dylib	    tiny_free_list_add_ptr
	4.1%	4.1%	libSystem.B.dylib	    __spin_lock
	0.3%	0.3%	libSystem.B.dylib	    dyld_stub__spin_lock
	9.6%	9.6%	libSystem.B.dylib	   szone_size
	1.2%	1.2%	libSystem.B.dylib	   malloc_zone_free
	0.5%	0.5%	libSystem.B.dylib	   dyld_stub_malloc_zone_free
	0.3%	0.3%	libSystem.B.dylib	   dyld_stub__spin_unlock
	0.2%	0.2%	libSystem.B.dylib	   spin_unlock
	5.5%	5.5%	libmozjs.dylib	  js::ArrayBuffer::class_finalize(JSContext*, JSObject*)
	0.5%	0.5%	libstdc++.6.dylib	  operator delete(void*)
	0.3%	0.3%	libSystem.B.dylib	  malloc_zone_free
	0.3%	0.3%	libmozjs.dylib	  dyld_stub_operator delete(void*)
	0.2%	0.2%	libmozjs.dylib	  TypedArrayTemplate<float>::class_finalize(JSContext*, JSObject*)
	0.2%	0.2%	libSystem.B.dylib	  szone_size
	0.2%	0.2%	libstdc++.6.dylib	  dyld_stub_free
	0.0%	0.2%	libgklayout.dylib	  _ZL24XPC_WN_NoHelper_FinalizeP9JSContextP8JSObject
	0.0%	16.6%	libmozjs.dylib	 JSCompartment::mark(JSTracer*)
	0.0%	16.6%	libmozjs.dylib	  _ZN2js2gcL12MarkChildrenEP8JSTracerP8JSObject
	0.0%	16.6%	libmozjs.dylib	   _ZN2js2gcL12MarkChildrenEP8JSTracerP8JSObject
	0.0%	16.6%	libmozjs.dylib	    _ZN2js2gcL12MarkChildrenEP8JSTracerP8JSObject
	0.0%	16.6%	libmozjs.dylib	     js_TraceObject(JSTracer*, JSObject*)
	0.0%	16.1%	libmozjs.dylib	      js_TraceObject(JSTracer*, JSObject*)
	0.0%	15.9%	libmozjs.dylib	       js_TraceObject(JSTracer*, JSObject*)
	1.2%	15.4%	libmozjs.dylib	        _ZL11array_traceP8JSTracerP8JSObject
	3.1%	13.8%	libmozjs.dylib	         js_TraceObject(JSTracer*, JSObject*)
	6.8%	9.1%	libmozjs.dylib	          _ZL11array_traceP8JSTracerP8JSObject
	2.2%	2.2%	libmozjs.dylib	           _ZL11array_traceP8JSTracerP8JSObject
	0.5%	1.4%	libmozjs.dylib	          js::Shape::trace(JSTracer*) const
	0.2%	0.2%	libmozjs.dylib	          JSObject::shrinkSlots(JSContext*, unsigned long)
	0.0%	0.2%	libmozjs.dylib	          js_TraceObject(JSTracer*, JSObject*)
	0.3%	0.3%	libmozjs.dylib	         _ZL11array_traceP8JSTracerP8JSObject
	0.0%	0.3%	libmozjs.dylib	        js_TraceObject(JSTracer*, JSObject*)
	0.0%	0.2%	libmozjs.dylib	        _ZN2js2gcL10MarkObjectEP8JSTracerR8JSObjectPKc
	0.0%	0.2%	libmozjs.dylib	       js::Shape::trace(JSTracer*) const
	0.2%	0.5%	libmozjs.dylib	      _ZL11array_traceP8JSTracerP8JSObject
	0.0%	1.2%	libgklayout.dylib	 _ZL13DOMGCCallbackP9JSContext10JSGCStatus
	0.0%	0.5%	libmozjs.dylib	 js::MarkRuntime(JSTracer*)
	0.2%	0.3%	libmozjs.dylib	 JSCompartment::purge(JSContext*)
	0.3%	0.3%	libmozjs.dylib	 js::ArrayBuffer::class_finalize(JSContext*, JSObject*)
	0.2%	0.2%	libmozjs.dylib	 TypedArrayTemplate<float>::class_finalize(JSContext*, JSObject*)
	0.0%	0.2%	libmozjs.dylib	 JSCompartment::sweep(JSContext*, unsigned int)
	0.2%	0.2%	libmozjs.dylib	 js_SweepAtomState(JSContext*)
	0.2%	0.2%	libmozjs.dylib	 js::PropertyTree::unmarkShapes(JSContext*)
	0.2%	0.2%	libSystem.B.dylib	 __bzero

Comment 1

[Olli Pettay [:smaug][[e-mail]]]

Btw, this is without the MaybeGC patch, so the stack looks like 
	0.0%	6.0%	libgklayout.dylib	                      nsJSContext::ScriptEvaluated(int)
	0.0%	6.0%	libmozjs.dylib	                       js::MaybeGC(JSContext*)
	0.0%	6.0%	libmozjs.dylib	                        js_GC(JSContext*, JSCompartment*, JSGCInvocationKind)
	0.5%	4.5%	libmozjs.dylib	                         JSCompartment::finalizeObjectArenaLists(JSContext*)
	0.3%	3.6%	libSystem.B.dylib	                          free

Comment 2

[Mike Shaver (:shaver -- probably not reading bugmail closely)]

Yep, fixed on tracemonkey even!

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

Great!