ac100 team mailing list archive

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 08/20/2011 04:07 PM, Julian Andres Klode wrote:
> On Sat, Aug 20, 2011 at 03:31:56PM +0100, Gordan Bobic wrote:
> > Which kernel are you using?
>
> A somewhat older build of Marc's kernel (one month), the one
> I have in my Debian repository + the change to use 1000 instead
> of 1200.

I presume you mean 1200mV rather than 1200MHz. If it's 1200MHz, I'd like 
to know where to tweak that. ;)

> > I just did the change to board-paz00-power.c reducing SM1 voltage
> > from 1200mV to 1000mV, and now I have been running the pbzip2 test
> > on a loop at low priority and recompiling glibc at normal priority,
> > and I've not been able to shake either of my AC100s loose. Since I
> > couldn't get anywhere near this sort of load before without
> > something erroring out, I'd say that this made quite a substantial
> > difference to stability.
>
> You probably did not run it at 1200 for 2 hours and then flashed
> a new kernel, rebooted, and tried another build directly. This
> might have caused certain parts to heat up already to an extent
> where it needs a bit of rest before running again. I expect it
> to work after a cold boot, though.

Well, my testing has been going on for 6+ hours. Considering I couldn't 
get an hour without errors before (and sometimes several/hour, and 
that's just the detected ones), I'd say it's a very definitive 
improvement. So much so that I'm vaguely tempted to try reducing it to 
950mV. ;)

> While we're at it (questions for you, and my answers to them)
>    (a) what cpufreq governor are you using? [performance]

Ondemand, but I haven't seen idle time move from 0.00%. each instance of 
pbzip2 should be running 2 threads, and it's all running in tmpfs. Plus 
the compiling job in the background for good measure. It's a fair point, 
though, I should really be testing with the performance governor.

>    (b) do you have battery plugged in? [no]

Yes. Why should this matter?

>    (c) where is gcc and source located? [btrfs on USB HDD]

All on the SD card, OS on ext4 without a journal, /usr/src (~/rpmbuild 
symlinked to /usr/src/rpmbuild) on nilfs2. The iowait time very rarely 
moves from 0%, and never exceeds low single figure % points.

> The problem here could also be related to the USB hard disk which
> is powered by the AC100, or the btrfs filesystem going crazy from
> time to time.

Plausible, but if you were seeing fs corruption, surely you'd have had 
bigger problems by now. Why btrfs, BTW?

> > Marc, could you please change this to 1000mV in git? Running at
> > 1200mV really seems to upset stability.
>
> Marc, as it helps Gordan, I support this. I'll do testing on a cold
> boot later today or tomorrow (that is, either soon or in about 19
> hours).


What would it take to break these voltages out to somewhere under /sys? 
It would be really handy for stability testing to not have to recompile 
and reflash the kernel for testing. I haven't done much kernel level 
programming before, but if there's a good example on how to break out 
interfaces to files under /sys that somebody can point me at, I'd be 
willing to have a go.

Gordan