This GLX Patch Can Really Boosts The FPS (~ +60%)
Written by Michael Larabel in Mesa on 26 January 2011 at 07:34 PM EST. 23 Comments
The past few months Chris Wilson has been on quite a coding spree with making many changes and improvements to the xf86-video-intel DDX driver, among other components. Today though he has put out a patch to the X.Org development list that will affect far more individuals than just those using the Intel graphics driver, which is his primary focus being an employee of the Intel Open-Source Technology Center. This GLX patch has boosted the in-game frame-rate for him in one of his tests by about sixty percent!

On the mailing list, Chris has supplied a patch entitled "glx: Cache indirect opcode->index conversion." He starts out by saying, "Decoding the opcode into the appropriate index into the dispatch tables is quite expensive using the radix tree. By keeping a small cache, we can dramatically speed up indirect function dispatch."

While this may not seem like anything exciting by just adding a cache for GLX opcode to index conversion for an end-users, what he says next is the exciting part. "World of Padman over the network increased from 28fps to 45fps, with an almost identical increase when run indirectly over a local socket." Yes, that's right, nearly a 60% increase in frame-rate from this simple patch. In the case of the Intel driver and other un-optimized graphics drivers or those running on low-power GPUs, this could mean the difference between a playable gaming experience and not, as is demonstrated by Chris' test with the frame-rate going from below-30 FPS to 45 FPS.

This patch is in the common GLX code so is not specific to any one driver too. However, to benefit from it you must be using indirect rendering.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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