Linux kernel and game performance?

Tom Spear speeddymon at
Fri Oct 29 12:44:21 CDT 2010

For the first reference, I have a WoW install. I haven't seen fps below 60
except in areas of the game where there are a lot of other players, but that
was under OpenGL back before the latest patch. I haven't tried since
Blizzard has disabled all high end settings in OpenGL mode for both Windows
and Linux, and I've heard nothing but bad performance on D3D recently. I
could give it a shot though. What is needed to make a kernel realtime other
than adding CONFIG_SCHED_DEBUG and adding the sysctl settings?



On Mon, Oct 25, 2010 at 6:26 PM, Dan Kegel <dank at> wrote:

> Hey folks,
> I've run into two web sites that claim that the Linux kernel causes
> performance
> problems in particular games (see below).  Anybody know of others?
> And has anybody found concrete improvements in performance
> of a particular app (other than an audio workstation app) from using
> a realtime kernel?
> Thanks!
> - Dan
> First:
> says in a section dated September 2008:
> "If you are having problems with choppy video every 15 seconds or so,
> it is related to the kernel scheduler...
> to fix, add CONFIG_SCHED_DEBUG=y to your kernel config, then set
> kernel.sched_features=21
> kernel.sched_batch_wakeup_granularity_ns=25000000
> kernel.sched_min_granularity_ns=4000000
> in /etc/sysctl.cfg."
> Yikes.  Any truth to that rumor?
> Second:
> says
> "The game runs too slowly
> Symptoms:
> Instead of running at about 60-62fps, like the game is supposed to,
> it'll run closer to 53fps. This is not ideal.
> The bug:
> This is a Linux timing issue. The game runs a secondary timing thread
> with THREAD_PRIORITY_TIME_CRITICAL, where it simply sleeps for 16ms
> and sends events to the main thread to tell it that a new frame is
> needed. On Linux the necessary timing accuracy is not available, so it
> wavers between 16ms and 20ms.
> The fix:
> I hacked around this by setting the timer period to 14ms. This leads
> to a steady 62-63fps. Which is close enough for use, really. For a
> constant 60fps turn on vsync in your video drivers."
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