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Re: Stability Under Load


On Sat, Aug 20, 2011 at 04:33:17PM +0100, Gordan Bobic wrote:
> 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 never said anything of Hz. It's all mV (if it's mV, what are 1.2V
used for? The voltage from the battery/charger is clearly 10-12V).

> 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. ;)

Given that the minimum it currently scales to would be 725, 950
is certainly save.
> >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.
But from my experience, scaling things are a bit broken, and you
do not get the same performance with ondemand, as it never really
tries to scale up much.

> >   (b) do you have battery plugged in? [no]
> Yes. Why should this matter?
Don't know. Not enough power from the AC at some periods
or stuff like this?

> >   (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?
I'm building Debian packages using sbuild in chroots managed by
schroot where each build runs in its own snapshot of a base chroot,
thus ensuring that the build environment is clean.

I could now use ext4 + aufs, but it would probably be slower than
my btrfs with nodatasum and fsync() disabled. Furthermore, cleanups
would be slower, as its not just a "delete this snapshot" thing
Julian Andres Klode  - Debian Developer, Ubuntu Member

See http://wiki.debian.org/JulianAndresKlode and http://jak-linux.org/.

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