From: Mark Nelson <mark.nelson@inktank.com>
To: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
Cc: "ceph-devel@vger.kernel.org" <ceph-devel@vger.kernel.org>
Subject: Re: extreme ceph-osd cpu load for rand. 4k write
Date: Thu, 08 Nov 2012 09:01:51 -0600 [thread overview]
Message-ID: <509BC95F.5090904@inktank.com> (raw)
In-Reply-To: <509BC878.3090804@profihost.ag>
Hi Stefan,
You might want to try running sysprof or perf while the OSDs are running
during the tests and see where CPU time is being spent. Also, how are
you determining how much CPU usage is being used?
Mark
On 11/08/2012 08:58 AM, Stefan Priebe - Profihost AG wrote:
> Is there any way to find out why a ceph-osd process takes around 10
> times more load on rand 4k writes than on 4k reads?
>
> Stefan
>
> Am 07.11.2012 21:41, schrieb Stefan Priebe:
>> Hello list,
>>
>> whiling benchmarking i was wondering, why the ceph-osd load is so
>> extreme high while having random 4k write i/o.
>>
>> Here an example while benchmarking:
>>
>> random 4k write: 16.000 iop/s 180% CPU Load in top from EACH ceph-osd
>> process
>>
>> random 4k read: 16.000 iop/s 19% CPU Load in top from EACH ceph-osd
>> process
>>
>> seq 4M write: 800MB/s 14% CPU Load in top from EACH ceph-osd process
>>
>> seq 4M read: 1600MB/s 9% CPU Load in top from EACH ceph-osd process
>>
>> I can't understand why in this single case the load is so EXTREMELY high.
>>
>> Greets
>> Stefan
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next prev parent reply other threads:[~2012-11-08 15:01 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-07 20:41 extreme ceph-osd cpu load for rand. 4k write Stefan Priebe
2012-11-08 14:58 ` Stefan Priebe - Profihost AG
2012-11-08 15:01 ` Sage Weil
2012-11-08 15:45 ` Stefan Priebe - Profihost AG
2012-11-08 16:06 ` Mark Nelson
2012-11-08 21:27 ` Stefan Priebe
2012-11-08 21:50 ` Josh Durgin
2012-11-08 21:58 ` Mark Nelson
2012-11-08 22:06 ` Stefan Priebe
2012-11-08 22:31 ` Stefan Priebe
2012-11-09 10:09 ` Stefan Priebe - Profihost AG
2012-11-09 10:21 ` Stefan Priebe - Profihost AG
2012-11-09 21:21 ` Samuel Just
2012-11-09 21:34 ` Stefan Priebe - Profihost AG
2012-11-10 20:36 ` Samuel Just
2012-11-10 20:37 ` Samuel Just
2012-11-10 20:43 ` Stefan Priebe
2012-11-10 20:42 ` Stefan Priebe
2012-11-08 15:01 ` Mark Nelson [this message]
2012-11-08 15:45 ` Stefan Priebe - Profihost AG
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