[Intel-gfx] Interrupt latency on some 945GM platforms

[Alexander Lam]

2010/9/26 Shaohua Li <shaohua.li at intel.com>

> 2010/9/26 Stefan Biereigel <security at biereigel-wb.de>:
> >  Am 24.09.2010 21:51, schrieb Jesse Barnes:
> >>
> >> On Fri, 24 Sep 2010 22:48:36 +0300
> >> Vasily Khoruzhick<anarsoul at gmail.com>  wrote:
> >>
> >>> On 24 of September 2010 22:39:01 Jesse Barnes wrote:
> >>>>
> >>>> On Thu, 16 Sep 2010 23:06:46 +0300
> >>>>
> >>>> Vasily Khoruzhick<anarsoul at gmail.com>  wrote:
> >>>>>
> >>>>> В сообщении от 16 of September 2010 21:50:50 автор Thomas Gleixner
> >>>
> >>> написал:
> >>>>>>
> >>>>>> Ok. The problematic part of HPET was not the clocksource, it was the
> >>>>>> clock event device which failed to deliver interrupts occasionally.
> It
> >>>>>> was worth a try at least.
> >>>>>
> >>>>> Hm, it seems that jerky glxgears is not related to jerky keyboard
> >>>>> events.
> >>>>> Keyboard is jerky only in konsole (kde terminal emulator), it seems
> >>>>> something happened it seems that font rendering performance is much
> >>>>> worse in latest xf86-video-intel than in xf86-video-intel-2.12.0.
> >>>>
> >>>> Len just had me try a few things too:
> >>>>   - maxcpus=1 lets things work
> >>>>   - offlining cpu1 at runtime (echo 0
> >>>>
> >>>>     >  /sys/devices/system/cpu/cpu1/online) lets things work
> >>>>
> >>>>   - binding the i915 interrupt to cpu 0 does *not* help
> >>>>
> >>>> Vasily and Paolo, do you both have Atom CPUs with hyperthreading
> >>>> enabled?
> >>>
> >>> Nope, I have Core2Duo T5500, dual-core, no hyperthreading :)
> >>
> >> Hm, well there goes the theory about Atom HT...
> >>
> >
> > Hello Everyone,
> > just to add on to reports of this problem, there was a Thread here in
> LKML
> > some months ago targeting the same problem (but not really attacking it
> at
> > the Chipset driver). As I have one of those Laptops with a 945GM-Chipset
> and
> > am stuck with the same Problem (disabled tickless now as a workaround and
> > set ticks to 1000) I could maybe do some testing of patches.
> > So what I can summarize is what the others did before: Disabling CPU1
> helps,
> > adding nohz=off helps, changing the Clocksource afterwards helps, binding
> > the Interrupt does NOT help.
> > So here's the Link to the old Discussion with follow-ups, maybe you can
> get
> > some furter information from there.
> > http://linux.derkeiler.com/Mailing-Lists/Kernel/2010-05/msg03696.html
> > We targeted the BIOS itself as everyone in this thread happened to own an
> > Phoenix BIOS with some special version string.
> > best, Stefan
> does disable msi help with 'pci=nomsi'?
>

Didn't help for me - besides, according to the KMS driver code, MSI is
disabled on 945G
I thought that maybe *enabling* MSI might help, but it seems 945 doesn't
support MSI according to the comments in the source.

Hardware: Acer Aspire One
Intel Atom N270 w/ 945GSE

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-- 
Alexander Lam
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