linux-kernel - Re: high system cpu load during intense disk i/o

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Date:	Mon, 06 Aug 2007 16:20:30 +0200
From:	Dimitrios Apostolou <jimis@....net>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org
Subject: Re: high system cpu load during intense disk i/o

Hello Andrew, thanks for your reply!


Andrew Morton wrote:
> On Sun, 5 Aug 2007 19:03:12 +0300 Dimitrios Apostolou <jimis@....net> wrote:
> 
>> was my report so complicated?
> 
> We're bad.
> 
> Seems that your context switch rate when running two instances of
> badblocks against two different disks went batshit insane.  It doesn't
> happen here.
> 
> Please capture the `vmstat 1' output while running the problematic
> workload.
> 
> The oom-killing could have been unrelated to the CPU load problem.  iirc
> badblocks uses a lot of memory, so it might have been genuine.  Keep an eye
> on the /proc/meminfo output and send the kernel dmesg output from the
> oom-killing event.

Please see the attached files. Unfortunately I don't see any useful info 
in them:
	*_before: before running any badblocks process
	*_while: while running badblocks process, but without any cron job 
having kicked in
	*_bad: 5 minutes later that some cron jobs kicked in

About the OOM killer, indeed I believe that it is unrelated. It started 
killing after about 2 days, that hundreds of processes were stuck as 
running and taking up memory, so I suppose the 256 MB RAM were truly 
filled. I just mentioned it because its behaviour is completely 
non-helpful. It doesn't touch the badblocks process, it rarely touches 
the stuck as running cron jobs, but it kills other irrelevant processes. 
If you still want the killing logs, tell me and I'll search for them.


Thanks,
Dimitris

View attachment "meminfo_bad.txt" of type "text/plain" (728 bytes)

View attachment "meminfo_before.txt" of type "text/plain" (728 bytes)

View attachment "meminfo_while.txt" of type "text/plain" (728 bytes)

View attachment "vmstat_bad.txt" of type "text/plain" (936 bytes)

View attachment "vmstat_before.txt" of type "text/plain" (944 bytes)

View attachment "vmstat_while.txt" of type "text/plain" (937 bytes)