By Luck, Marek Discovers A "Serious Performance Fix" For RadeonSI

Written by Michael Larabel in Radeon on 12 October 2016 at 05:47 PM EDT. 43 Comments
Marek Olšák, the prolific longtime contributor to Mesa and AMD developer, published a patch today with a big performance improvement that he says has been discovered by luck.

Hitting the Mesa mailing list this afternoon was a RadeonSI patch to disable ReZ. His comment was simply, "This is a serious performance fix. Discovered by luck."

In the patch a code comment he added warns, "DON'T USE EARLY_Z_THEN_RE_Z !!!" He found this code caused a performance decrease of 15% with DiRT Showdown on ultra quality settings.

By deleting this case of using EARLY_Z_THEN_RE_Z, this small patch allows for better performance. This should also help other Linux games on RadeonSI making use of complex shaders.
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