[Webkit-unassigned] [Bug 234920] ImageBitmap has poor performance on iOS

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=234920

--- Comment #2 from Simon Taylor <simontaylor1 at ntlworld.com> ---
Created attachment 448498

  --> https://bugs.webkit.org/attachment.cgi?id=448498&action=review

System Trace for texImage2d(imageBitmap)

System trace shows the content process blocked for 14ms for each upload call, in RemoteRenderingBackendProxy::getShareableBitmap. It looks to have the same cost each time, even when the ImageBitmap hasn't been changed (just from the naming I would have expected the "sharable bitmap" to be pretty quick to share if it hasn't changed...)

On the GPU process, the stack looks to be GraphicsContextCG::drawNativeImage inside getShareableBitmapForImageBuffer where all the time is taken. There's also a huge number of virtual memory zero-fill operations during that time (perhaps one per scanline?)

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