Bug 23510 - XvPutImage uses oversized buffers when rendering sub-regions of source YUV buffers
Summary: XvPutImage uses oversized buffers when rendering sub-regions of source YUV bu...
Alias: None
Product: xorg
Classification: Unclassified
Component: Driver/intel (show other bugs)
Version: 7.4 (2008.09)
Hardware: Other All
: medium enhancement
Assignee: haihao
QA Contact: Xorg Project Team
Keywords: patch
Depends on:
Reported: 2009-08-25 10:15 UTC by Hugo Jacques
Modified: 2010-07-17 07:01 UTC (History)
0 users

See Also:
i915 platform:
i915 features:

patch to dramatically reduce CPU usage (6.55 KB, patch)
2009-08-25 10:15 UTC, Hugo Jacques
no flags Details | Splinter Review

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.

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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