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From: Christian Schmidt <schmidt@digadd.de>
To: dm-crypt@saout.de
Cc: linux-kernel@vger.kernel.org
Subject: [dm-crypt] kworkers for dm-crypt locked to CPU core 0?
Date: Mon, 25 Mar 2013 10:42:34 +0100	[thread overview]
Message-ID: <51501C0A.5060406@digadd.de> (raw)

Hi everyone,

I am trying to troubleshoot some strange performance issues I am seeing
on a machine of mine. Said machine had 10 drives mapped via separate
dm-crypt instances. The aggregate (read) throughput seems to hover
around 120-130MB/s (looking at iostat -x -d) when running an instance of
dd if=/dev/dm-<instance> of=/dev/null bs=1m for each mapping. However
"top" shows that one core is loaded with 99% system tasks, and two to
three cores are spinning in iowait. All the kworkers get their share of
roughly 10% CPU.

"taskset" shows that all of the kworkers have an affinity mask of 1, so
they can run on core 0 only, and trying to change it results in an error
of "Invalid argument".

Is there a way I can make the scheduler put those on multiple cores?

Please cc: me since I am not subscribed.

Regards,
Christian

WARNING: multiple messages have this Message-ID (diff)
From: Christian Schmidt <schmidt@digadd.de>
To: dm-crypt@saout.de
Cc: linux-kernel@vger.kernel.org
Subject: kworkers for dm-crypt locked to CPU core 0?
Date: Mon, 25 Mar 2013 10:42:34 +0100	[thread overview]
Message-ID: <51501C0A.5060406@digadd.de> (raw)

Hi everyone,

I am trying to troubleshoot some strange performance issues I am seeing
on a machine of mine. Said machine had 10 drives mapped via separate
dm-crypt instances. The aggregate (read) throughput seems to hover
around 120-130MB/s (looking at iostat -x -d) when running an instance of
dd if=/dev/dm-<instance> of=/dev/null bs=1m for each mapping. However
"top" shows that one core is loaded with 99% system tasks, and two to
three cores are spinning in iowait. All the kworkers get their share of
roughly 10% CPU.

"taskset" shows that all of the kworkers have an affinity mask of 1, so
they can run on core 0 only, and trying to change it results in an error
of "Invalid argument".

Is there a way I can make the scheduler put those on multiple cores?

Please cc: me since I am not subscribed.

Regards,
Christian

             reply	other threads:[~2013-03-25 10:10 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-03-25  9:42 Christian Schmidt [this message]
2013-03-25  9:42 ` kworkers for dm-crypt locked to CPU core 0? Christian Schmidt
2013-03-25 10:32 ` [dm-crypt] " Andi Kleen
2013-03-25 10:32   ` Andi Kleen
2013-03-25 10:55   ` [dm-crypt] " Christian Schmidt
2013-03-25 10:55     ` Christian Schmidt

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