From: Stefan Hajnoczi <stefanha@gmail.com>
To: Gleb Stepanov <gstepanov@mirantis.com>
Cc: qemu-devel@nongnu.org, qemu-discuss@nongnu.org
Subject: Re: [Qemu-devel] Write requests, during read operations
Date: Thu, 16 Jul 2015 14:35:19 +0100 [thread overview]
Message-ID: <20150716133519.GE16984@stefanha-thinkpad.redhat.com> (raw)
In-Reply-To: <CAKk_wU4yVYqAiHSs7edWVFZ1fp1UkFCF2WG0+WsGQ_3uZePe_w@mail.gmail.com>
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On Tue, Jul 14, 2015 at 05:39:13PM +0300, Gleb Stepanov wrote:
> I've measured performance on qcow2 image mounted to nb0 device.
nb0 device?
> I run tests and
> launch iostat -x 1 command to browse I/O operations. Test consists of
> sequential read operations with 1 MB size. I've get following output.
>
> Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s
> sda 0.00 5.00 0.00 677.00 0.00 22812.00
> sdb 0.00 0.00 0.00 545.00 0.00 0.00
> dm-0 0.00 0.00 0.00 674.00 0.00 22784.00
> dm-1 0.00 0.00 0.00 7.00 0.00 28.00
> dm-2 0.00 0.00 0.00 0.00 0.00 0.00
> nb0 0.00 0.00 432.00 182.00 55296.00 23296.00
>
> So, reading produce a lot of write operations. What is the reason why
> these write operations occured?
> How to determina block size that qemu operates , because if i've
> writtien 55 mb with 1 mb blocks
> i should get 55 operations instead of 432.
Please post details of the benchmark:
* fio job file and fio command-line
* commands used to launch QEMU or qemu-nbd
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prev parent reply other threads:[~2015-07-16 13:35 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-14 14:39 [Qemu-devel] Write requests, during read operations Gleb Stepanov
2015-07-16 13:35 ` Stefan Hajnoczi [this message]
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