[Webkit-unassigned] [Bug 97866] New: Memory increase by uncontrolled decoded Image data after clearing cache

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=97866

           Summary: Memory increase by uncontrolled decoded Image data
                    after clearing cache
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
               URL: http://www.slrclub.com/bbs/vx2.php?id=slr_review&page=
                    1&divpage=1&select_arrange=headnum&desc=asc&no=284
        OS/Version: All
            Status: UNCONFIRMED
          Severity: Critical
          Priority: P2
         Component: WebCore Misc.
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: tros07 at gmail.com


I found critical problem for controlling image decoded data after user selected clear cache menu.
This problem can be detected with above webpage address on chrome and safari browser.

[Step]
1. Access above address. That page contains a lot of jpeg images.
2. Scroll whole page.
3. Select "cache clear" menu on each browser menu.
4. Scroll whole page again.
5. Compare memory size of step2 with that of step4.

Memory increase of each tab page
[chrome]
180MB -> 500MB
[safari]
520MB -> 780MB

The cause of this problem is that all elements are removed from resource list after calling evictResources() although some resources of current page cannot be deleted.
As you know, decoded Image Data should be controlled by prune() or any other method.
However, because there is no elements in resource list after clear cache, memoryCache cannot remove old decoded data and stack all decoded data of current page.

I attach a patch for this problem.

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