Bug 23510

Summary: XvPutImage uses oversized buffers when rendering sub-regions of source YUV buffers
Product: xorg Reporter: Hugo Jacques <hugo.jacques>
Component: Driver/intelAssignee: haihao <haihao.xiang>
Status: RESOLVED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: enhancement    
Priority: medium Keywords: patch
Version: 7.4 (2008.09)   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
patch to dramatically reduce CPU usage none

Description Hugo Jacques 2009-08-25 10:15:14 UTC 
Created attachment 28900 [details] [review]
patch to dramatically reduce CPU usage

I recently noticed that X seemed to take far more CPU when displaying a YV12 small rectangle (say 704x480) out of a large YUV source buffer (say 2048x1088)using XvShmPutImage than it was when the source YUV buffer was 704x480.

Looking at the code in i830PutImage (i830_video.c), I realized that the destination buffer for I830CopyPlanarData and the likes was way too large in the case I just described.
In fact, it was the same size (+/- pitch alignment) as the whole source YUV buffer.

Attached is a patch that sizes it as the source sub-rectangle within the whole source YUB buffer, adjusted for clipping and pitch alignment.

Performance improvement were dramatic: 30 frames/second of 704x480 from a 2048x1088 source used to have X take 10% of the CPU. Now it merely takes 3%.

Please review (I'm not an Intel video driver guru and I might have overlooked some issues. Plus I could not test all the possible cases.) and commit for everybody's enjoyment :)

i810PutImage might eventually also benefit from this type of improvement.

Hugo
Comment 1 Gordon Jin 2009-08-25 18:13:37 UTC 
haihao, can you review?
Comment 2 Chris Wilson 2010-07-17 07:01:51 UTC 
The current code is using nlines and npixels to trim the copied region.

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