[ubuntu-x] -intel 2.6.3 uploaded

Bryce Harrington bryce at canonical.com
Tue Mar 24 01:03:07 GMT 2009


On Tue, Mar 24, 2009 at 12:15:52AM +0000, Peter Clifton wrote:
> On Tue, 2009-03-24 at 00:29 +0100, Khashayar Naderehvandi wrote:
> > On Mon, Mar 23, 2009 at 11:12 PM, Bryce Harrington <bryce at canonical.com> wrote:
> > > On Mon, Mar 23, 2009 at 09:49:38PM +0000, Peter Clifton wrote:
> > >> On Mon, 2009-03-23 at 13:12 -0700, Bryce Harrington wrote:
> > >> > For those of you who have tested UXA, now that -intel 2.6.3 has been in
> > >> > the archive a few days, what are your thoughts on it compared with the
> > >> > default EXA?
> > >>
> > Well, for me things are much better with UXA (on g45), except for one
> > thing, which in fact is a show stopper. Namely, the issue that a
> > suspend/resume cycle while either compiz or composited kwin is active,
> > 2 out of 3 times crashes the server and leaves me at the login window.
> > So I'd vote for EXA, although performance is pretty crappy with it.
> 
> Ah, I see that too, but hadn't tied it to DRI2 / UXA / Compiz.

Is there a bug report open on this issue?
(If not, someone care to submit one?) 

> > >> I noted this blog post today:
> > >>
> > >> http://jasondclinton.livejournal.com/72910.html
> > >>
> > >> And it seems that the cpufreq governer being broken causes low fps / 3D
> > >> performance. I seem to recall some kernel fixes in Jaunty to reinstate
> > >> the ondemand governor. Perhaps my brief spell with no proper CPU
> > >> governor corresponded to the increased FPS.
> > >>
> > >> (Setting the "performance" governor rather than "ondemand" pushes my
> > >> "not a benchmark" glxgears numbers from about 560fps to about 880fps.)
> > >
> > > Hey, that's interesting.  That could also explain why people with
> > > exactly the same graphics chipsets are reporting drastically varying
> > > performance results.
> > >
> > > Anyone else with -intel performance troubles see it go away if switching
> > > from ondemand to performance?
> > >
> > I came across that blog post as well and found it interesting. It
> > helps performance a little to follow the advice on that blog post when
> > running games and the likes. But when I'm talking about reduced
> > performance, I'm always talking about compiz and/or composited kwin.
> > That is, normal everyday stuff that should be running fine without the
> > performance governor. And with EXA normal desktop usage is OK, but not
> > great. It should be much better with a g45.
> 
> glxgears "looks" CPU bound when running with the "ondemand" governer (it
> takes about half the monitoring applet's graph on my core2 duo laptop).
> "top" shows otherwise:
> 
> (ondemand, running at 800Mhzm both cores)
> 
> Cpu0  : 15.3%us, 15.0%sy,  0.0%ni, 68.3%id,  0.0%wa,  1.3%hi,  0.0%si,  0.0%st
> Cpu1  : 33.2%us, 24.1%sy,  0.0%ni, 41.8%id,  0.0%wa,  0.9%hi,  0.0%si,  0.0%st
> 
> glxgears ~ 500fps.
> 
> (performance, running at 2.4Ghz both cores)
> 
> Cpu0  :  8.7%us,  6.0%sy,  0.0%ni, 82.0%id,  1.3%wa,  2.0%hi,  0.0%si,  0.0%st
> Cpu1  : 11.2%us, 11.2%sy,  0.0%ni, 72.6%id,  0.0%wa,  4.9%hi,  0.0%si,  0.0%st
> 
> glxgears ~800fps.
> 
> I wonder if the changes in cpufreq are affecting the timing of
> opportunities for some required synchronisation between the CPU and GPU.
> Clearly the frame-rate doesn't appear to be CPU bound as the blog post
> suggests. (Unless some kernel CPU time simply isn't being accounted for,
> and is lost to cpufreq and "top".).
> 
> Another off the wall idea.. could the platform methods used to change
> the speed of the CPU core be somehow triggering similar reduction in
> execution speed in the graphics chipset?

Heh, that's what I was just wondering looking at those numbers.  I
assume you've verified you're not using software rendering in glxinfo
(I'd guess the fps numbers would be lower in such a case anyway.)

> Here's a really fun discovery.. I ran a short test program to busy-loop
> the CPU. This is with the "performance" governer. After running one
> copy, my glxgears fps appeared to increase. Curious, I spawned a second
> copy (I have 2 cores of CPU). glxgears fps increased again! (to
> ~950fps). Just for completeness' sake, I'll note that a third copy slows
> it down again somewhat.
> 
> The busy-loop programs are keeping the CPU from idling, and perhaps
> somehow the residency of lower C states is giving rise to the lower
> frame-rates (in spite the CPU being otherwise busy).

Interesting, that does suggest some sort of processor sleep/wakeup
overhead effect.
 
> I'm also not a gamer, so can't comment how these findings might apply to
> "real-world" work-loads.

I've been encouraging people to run 3D games (I've tested with
sauerbraten) as a more realistic workload.

Bryce




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