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?<br>
<br clear="all">Thanks<br><br>Tom<br>
<br><br><div class="gmail_quote">On Mon, Oct 25, 2010 at 6:26 PM, Dan Kegel <span dir="ltr"><<a href="mailto:dank@kegel.com">dank@kegel.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
Hey folks,<br>
I've run into two web sites that claim that the Linux kernel causes performance<br>
problems in particular games (see below). Anybody know of others?<br>
<br>
And has anybody found concrete improvements in performance<br>
of a particular app (other than an audio workstation app) from using<br>
a realtime kernel?<br>
<br>
Thanks!<br>
- Dan<br>
<br>
First:<br>
<br>
<a href="http://wiki.archlinux.org/index.php/World_of_Warcraft#Kernel_Timing_Bug" target="_blank">http://wiki.archlinux.org/index.php/World_of_Warcraft#Kernel_Timing_Bug</a><br>
says in a section dated September 2008:<br>
"If you are having problems with choppy video every 15 seconds or so,<br>
it is related to the kernel scheduler...<br>
to fix, add CONFIG_SCHED_DEBUG=y to your kernel config, then set<br>
kernel.sched_features=21<br>
kernel.sched_batch_wakeup_granularity_ns=25000000<br>
kernel.sched_min_granularity_ns=4000000<br>
in /etc/sysctl.cfg."<br>
<br>
Yikes. Any truth to that rumor?<br>
<br>
Second:<br>
<br>
<a href="http://hisouten.koumakan.jp/wiki/Linux_support#Resolved_bugs" target="_blank">http://hisouten.koumakan.jp/wiki/Linux_support#Resolved_bugs</a><br>
says<br>
<br>
"The game runs too slowly<br>
Symptoms:<br>
Instead of running at about 60-62fps, like the game is supposed to,<br>
it'll run closer to 53fps. This is not ideal.<br>
The bug:<br>
This is a Linux timing issue. The game runs a secondary timing thread<br>
with THREAD_PRIORITY_TIME_CRITICAL, where it simply sleeps for 16ms<br>
and sends events to the main thread to tell it that a new frame is<br>
needed. On Linux the necessary timing accuracy is not available, so it<br>
wavers between 16ms and 20ms.<br>
The fix:<br>
I hacked around this by setting the timer period to 14ms. This leads<br>
to a steady 62-63fps. Which is close enough for use, really. For a<br>
constant 60fps turn on vsync in your video drivers."<br>
<br>
<br>
</blockquote></div><br>