[Webkit-unassigned] [Bug 111644] New: [meta] RecalcStyle accounts for too much time on the main thread

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=111644

           Summary: [meta] RecalcStyle accounts for too much time on the
                    main thread
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: eric at webkit.org
                CC: eae at chromium.org


[meta] RecalcStyle accounts for too much time on the main thread

In previous of Telemetry using Chromium content_shell on an Android device, we see style recalc taking up as much as 24% of total mainthread time.

https://docs.google.com/spreadsheet/ccc?key=0AlC4tS7Ao1fIdGtJTWlSaUItQ1hYaDFDcWkzeVAxOGc#gid=0
is a very run, but I will add more recent runs in further comments.

This is a meta bug to track planned work of making this take up less main-thread time.  I expect we will take several approaches, including:
- Remove unnecessary recalcs (by deferring the work as much as possible)
- Make parts of recalc faster (for example canShareStyleWith() is very very hot)
- Explore radical ideas such as making style recalc resume-able (resolve only as much of the docuement as is needed to answer a specific query) or computable by parallel threads.

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