[Mesa-dev] [Bug 55998] Pretty huge slowdown in mesa 9.0

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Mon Oct 29 17:11:38 PDT 2012


--- Comment #19 from Kenneth Graunke <kenneth at whitecape.org> ---
Created attachment 69265
  --> https://bugs.freedesktop.org/attachment.cgi?id=69265&action=edit
Bisect log (Kayden)

I managed to reproduce this after all.

Steps to reproduce:
1. Enable KWin's "Show FPS" counter plugin.
2. Configure the "Present Windows" effect to one of the screen corners.
3. Mash that repeatedly and watch the FPS counter.

On HD 4000, a good version of Mesa results in perhaps ~55-60 FPS.  Bad Mesa can
be as low as 17 FPS, often mid-30s.

I also went ahead and bisected it (the log is attached).

e943e5c291c5f4c017f9f5a483f1940313333fc3 is the first bad commit
commit e943e5c291c5f4c017f9f5a483f1940313333fc3
Author: Chad Versace <chad.versace at linux.intel.com>
Date:   Thu Aug 2 17:13:17 2012 -0700

    intel: Advertise multisample DRI2 configs on gen >= 6

    This turns on window system MSAA.

So in other words, it looks like KDE is using multisampling now, whereas it
didn't before.  Our implementation of that may not be optimal, and may have
bugs, but it will always be far slower than single sampling.

My next question would be: how can one disable the use of MSAA in KWin or
Plasma?  I don't see an option for that, but I would be really surprised if
there wasn't one...

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