From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Priebe - Profihost AG Subject: Re: speedup ceph / scaling / find the bottleneck Date: Fri, 29 Jun 2012 15:02:47 +0200 Message-ID: <4FEDA777.1060309@profihost.ag> References: <4FED8792.1090905@profihost.ag> <4FED964D.3080201@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail.profihost.ag ([85.158.179.208]:53051 "EHLO mail.profihost.ag" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754579Ab2F2NCz (ORCPT ); Fri, 29 Jun 2012 09:02:55 -0400 In-Reply-To: <4FED964D.3080201@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Mark Nelson Cc: "ceph-devel@vger.kernel.org" Am 29.06.2012 13:49, schrieb Mark Nelson: > I'll try to replicate your findings in house. I've got some other > things I have to do today, but hopefully I can take a look next week. If > I recall correctly, in the other thread you said that sequential writes > are using much less CPU time on your systems? Random 4k writes: 10% idle Seq 4k writes: !! 99,7% !! idle Seq 4M writes: 90% idle > Do you see better scaling in that case? 3 osd nodes: 1 VM: Rand 4k writes: 7000 iops Seq 4k writes: 19900 iops 2 VMs: Rand 4k writes: 6000 iops each Seq 4k writes: 4000 iops each VM 1 Seq 4k writes: 18500 iops each VM 2 4 osd nodes: 1 VM: Rand 4k writes: 14400 iops Seq 4k writes: 19000 iops 2 VMs: Rand 4k writes: 7000 iops each Seq 4k writes: 18000 iops each > To figure out where CPU is being used, you could try various options: > oprofile, perf, valgrind, strace. Each has it's own advantages. > > Here's how you can create a simple callgraph with perf: > > http://lwn.net/Articles/340010/ 10s perf data output while doing random 4k writes: https://raw.github.com/gist/2c16136faebec381ae35/09e6de68a5461a198430a9ec19dfd5392f276706/gistfile1.txt Stefan