Tune GC related JSC options for iOS

[Michael Saboff]

Empirical tests show that iOS devices perform better with the options values overridden for a smaller number of cores in Options.cpp:overrideDefaults().

These are the options in question:
    Options::maximumMutatorUtilization() = 0.6;
    Options::concurrentGCMaxHeadroom() = 1.4;
    Options::minimumGCPauseMS() = 1;
    Options::useStochasticMutatorScheduler() = false;

<rdar://problem/31718721>

[Michael Saboff]

Created attachment 307517 [details]
Patch

[Mark Lam]

Comment on attachment 307517 [details]
Patch

r=me

[JF Bastien]

Comment on attachment 307517 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=307517&action=review

r=me

> Source/JavaScriptCore/runtime/Options.cpp:335
> +    {

Would it be better to duplicate the block below for iOS and not iOS, or do we expect the tuning parameters to stay the same for both (only the condition above changes)?

[Michael Saboff]

(In reply to JF Bastien from comment #3)
> Comment on attachment 307517 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=307517&action=review
> 
> r=me
> 
> > Source/JavaScriptCore/runtime/Options.cpp:335
> > +    {
> 
> Would it be better to duplicate the block below for iOS and not iOS, or do
> we expect the tuning parameters to stay the same for both (only the
> condition above changes)?

I opted to do it this way since these are all GC related and don't expect them to change.

[Michael Saboff]

Committed r215539: <http://trac.webkit.org/changeset/215539>

[Filip Pizlo]

Comment on attachment 307517 [details]
Patch

R=me too