Re: High %wa, irregular blocking
Hi
On Wed, Jun 04, 2014 at 08:49:44AM +0200, b-misc@gmx.ch wrote:
> Hi,
>
> Some weeks ago I installed Testing on my wife's iMac [1] from 2008.
> Unfortunately it has one issue:
>
> There are irregular periods of very high %wa, maybe 3-5 times per hour, not
> directly related to a certain user action. They last for some seconds up to
> even a minute or so and render the machine unusable for that time. top shows %wa
> of 80 or 90%, load can go up to 9 on this dual core machine, iotop shows only a
> few KB/s.
High wait-for-IO combined with very little disk throughput usually
points towards disk problems...
Anything interesting from e.g. "iostat -kNx" ? That should tell you
which disk and partition is suffering. (Or if you already think you
know, this should confirm it)
>
> I already added pcie_aspm=off to the boot options which seems to help,
> but I still see this I/O hangs (without, I had about 10+ hangs per hour).
>
> Any idea what could cause these blockings? How can I find out more? I use Linux
> for 15+ years but I never saw such things... and I want to show my
> wife, that Linux is the better OS, of course... ;-)
My first call would be the kernel logs. IIRC in the default syslog
config this goes to /var/log/kern.log, but you can see the most recent
output with e.g. "dmesg" or "dmesg -T"
Combine this with the disk-related snippets from /var/log/dmesg (which
has the kernel output from boot) and you may see further clues...
Which kernel are you using? Stock kernel, or self-compiled? 32bit?
64bit?
The firmware version may also be relevant here.
>
> Aside from that issue everything runs quite nicely.
>
> Thanks & best regards,
> Bernd
>
> [1] iMac 8,1: 2008, Core 2 Duo 2.8 GHz, GB RAM, 500 GB WD HDD, ATI Radeon HD
> 2600 PRO (PCIe)
Looks similar to this one? http://www.odi.ch/prog/macbookpro/#3
Hope this helps
--
Karl E. Jorgensen
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