Bug 61004 – move fastCheckSelector call into SelectorChecker in preparation for querySelector using it

• Component: New Bugs
• Status: RESOLVED INVALID

[Ojan Vafai]

move fastCheckSelector call into SelectorChecker in preparation for querySelector using it

[Ojan Vafai]

Created attachment 93846 [details]
Patch

[Ojan Vafai]

To make querySelector go down this codepath, we'll use a dummy RuleData object. I've prototyped this locally, and, at least in some cases, it's much faster (e.g. 4x). 

The downside is that regular selector matching is possibly 0.5% slower. I ran the test case in the patch under sample and aggregated the matchRules(...) calls. I did 30 iterations with a clean build and 30 iterations with this patch. It's hard to be 100% sure given the large standard deviation. Including the data below:

clean:
Min.     Median    Mean     Max.     Stddev
278.0   305.0      307.4    361.0   19.1
Raw  data: 338,315,284,361,303,291,293,287,303,294,310,325,278,327,318,311,335,291,331,295,286,295,307,292,318,304,323,306,289,313


modified:
Min.     Median    Mean     Max.      Stddev
278.0   308.0      309.5    335.0    16.8
Raw  data: 316,285,321,316,300,330,297,307,305,317,310,294,278,307,289,300,312,309,335,306,301,333,291,322,280,335,296,332,327,333

I was surprised to see this cause any performance difference, so I confirmed that the disassembly for matchRulesForList is in fact different between the two builds.

I'm open to suggestions for how to do this differently that might not have any performance impact or how to get a testcase with less variability.

[Ojan Vafai]

I wanted to get this patch in separately since this is the only performance sensitive part of the patch to make querySelector use fastCheckSelector.

[Ojan Vafai]

Comment on attachment 93846 [details]
Patch

Hm. I'm not sure the patch this one is trying to enable makes sense actually. I had a bug in my performance measurement. I'll remove the r? while I figure it out.

[Antti Koivisto]

All these checkSelector functions are kinda confusing. It would be nice not to add new ones.