Intel Driver Is Now Doing Triple-Bufferred Page-Flips
Written by Michael Larabel in Intel on 12 July 2011 at 07:48 AM EDT. 4 Comments
The Intel Linux X.Org driver is now doing triple-buffered page-flips in the latest attempt to battle imperfect frames with tears or jitters. This is now the default behavior with the next xf86-video-intel release.

Rather than simply page-flipping just between a front and back-buffer, the Intel DDX now has a third buffer. This third buffer, the draw buffer, is supplied immediately upon the front-buffer being flipped so that the application rendering isn't blocked temporarily while waiting for the current front-buffer to be swapped away from the scan-out. This should basically work around jitters by always having a frame ready rather than hitting cases where rendering a new frame may take longer than the frame interval length. Or in other words, the frame-rate being stuck at 30 and/or 60 FPS. The downside is that you just have an extra frame of latency. This triple-buffering on applies to Intel KMS page-flipping.

This triple-bufferred page-flipping was introduced via this commit by Chris Wilson. For anyone wishing to revert to the old behavior, there's now a TripleBuffer xorg.conf option to disable the said functionality.
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Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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