[WebCore] Shrink sizeof(RuleFeature)

[Yusuke Suzuki]

[WebCore] Shrink sizeof(RuleFeature)

[Yusuke Suzuki]

Created attachment 386779 [details]
Patch

[Yusuke Suzuki]

Comment on attachment 386779 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=386779&action=review

> Source/WebCore/style/RuleFeature.h:42
>  struct RuleFeature {

I'm still thinking about further reduction of size.
1. matchElement is used in some specific places. Most of RuleFeature does not have this.
2. selectorListIndex is only used for CSSJIT. I think we could remove it, move it to other place, or recalculate it.
3. We could use PackedRefPtr<const StyleRule>, which is 6 byte.
If we do that, we could make RuleFeature,

struct RuleFeature {
    PackedRefPtr<const StyleRule> styleRule;
    uint16_t selectorIndex;
}; 

Then, sizeof(RuleFeature) is 8 bytes. For now, I postpone this.

[Antti Koivisto]

Comment on attachment 386779 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=386779&action=review

> Source/WebCore/ChangeLog:8
> +        We noticed that Vector<RuleFeature> is frequently allocated and kept. While sizeof(RuleFeature) is 32,

What sort of memory usage did you see here in the worst cases?

[Yusuke Suzuki]

Comment on attachment 386779 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=386779&action=review

>> Source/WebCore/ChangeLog:8
>> +        We noticed that Vector<RuleFeature> is frequently allocated and kept. While sizeof(RuleFeature) is 32,
> 
> What sort of memory usage did you see here in the worst cases?

In Gmail, it is using 100KB + 56KB + ...

[Yusuke Suzuki]

Committed r254065: <https://trac.webkit.org/changeset/254065>

[Radar WebKit Bug Importer]

<rdar://problem/58347222>