[Webkit-unassigned] [Bug 82816] New: presentationAttributeCacheMaximumSize is set too low

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=82816

           Summary: presentationAttributeCacheMaximumSize is set too low
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: CSS
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: jchaffraix at webkit.org


Before bug 77204, the presentation attribute style (called matched declaration at the time) cache used to grow unbounded. Bug 80707 re-introduced the missing cache and set the limit to 128 which gave around a 75% hit rate. This is however a regression from the original caching for a few reasons:
- the hit rate on the previous cache was higher in the 85% range (beware it's not an apple-to-apple comparison due to the different modeling used for attribute styles, see 2nd point)
- due to the new mapping (several attributes to one style vs 1 attribute to 1 style before), there is a combinatorial explosion compared to the previous (more simple) model.

Any cache miss in this cache, unfortunately means that we *will* miss in our matched property cache as we are doing pointer comparisons. This bug proposes to bump the cache size to get back some of the performance.

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