public inbox for kvm@vger.kernel.org
 help / color / mirror / Atom feed
From: Thomas Mueller <thomas@chaschperli.ch>
To: kvm@vger.kernel.org
Subject: Re: qcow2 slowdown in kvm-78,79
Date: Wed, 19 Nov 2008 19:49:24 +0000 (UTC)	[thread overview]
Message-ID: <gg1qk4$bap$1@ger.gmane.org> (raw)
In-Reply-To: 49245A61.9050504@codemonkey.ws

On Wed, 19 Nov 2008 12:26:41 -0600, Anthony Liguori wrote:

> Ryan Harper wrote:
>> * Henrik Holst <henrik@witsbits.com> [2008-11-18 08:42]:
>>   
>>> The bundled qemu in kvm-78 and kvm-79 slows down disk i/o with qcow2
>>> images by an order of 10. If one got 60MB/s before, one gets around
>>> 6MB/s with 78 and 79 (measured with dd)
>>>     
>>>     
>> dd command?
>>
>> what's your -drive parameters look like, specifically, what if type?
>> ide, scsi, virtio?
>>   
>>   
> This is probably the change to cache=writethrough.  I bet if you set
> cache=writeback then you'll see this go away.

this was it. cache=writeback and the throughput goes from 10mb/s to 80/mb/
s with if=scsi

thanks.

- Thomas


  reply	other threads:[~2008-11-19 19:49 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-11-18 14:39 qcow2 slowdown in kvm-78,79 Henrik Holst
2008-11-19 17:55 ` Thomas Mueller
2008-11-19 18:23 ` Ryan Harper
2008-11-19 18:26   ` Anthony Liguori
2008-11-19 19:49     ` Thomas Mueller [this message]
2008-11-19 22:06       ` Anthony Liguori
2008-11-19 23:47     ` walt
2008-11-20  1:00       ` Anthony Liguori
2008-11-20  7:57     ` Henrik Holst
2008-11-20  8:08       ` Henrik Holst

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='gg1qk4$bap$1@ger.gmane.org' \
    --to=thomas@chaschperli.ch \
    --cc=kvm@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox