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From: Thomas Mueller <thomas@chaschperli.ch>
To: kvm@vger.kernel.org
Subject: Re: Shouldn't cache=none be the default for drives?
Date: Thu, 8 Apr 2010 05:07:02 +0000 (UTC)	[thread overview]
Message-ID: <hpjo9m$tv8$1@dough.gmane.org> (raw)
In-Reply-To: 4BBC992D.3050905@gmail.com

Am Wed, 07 Apr 2010 16:39:41 +0200 schrieb Troels Arvin:

> Hello,
> 
> I'm conducting some performancetests with KVM-virtualized CentOSes. One
> thing I noticed is that guest I/O performance seems to be significantly
> better for virtio-based block devices ("drive"s) if the cache=none
> argument is used. (This was with a rather powerful storage system
> backend which is hard to saturate.)
> 
> So: Why isn't cache=none be the default for drives?

while ago i suffered poor performance of virtio and win2008. 

This helped alot:

I enabled "deadline" block scheduler instead of the default "cfq" on the 
host system. tested with: Host Debian with scheduler deadline, Guest 
Win2008 with Virtio and cache=none. (26MB/s to 50MB/s boost measured) 
Maybe this is also true for Linux/Linux.

I expect that scheduler "noop" for linux guests would be good.

- Thomas



  parent reply	other threads:[~2010-04-08  5:07 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-04-07 14:39 Shouldn't cache=none be the default for drives? Troels Arvin
2010-04-07 15:17 ` Gordan Bobic
2010-04-08  5:07 ` Thomas Mueller [this message]
2010-04-08  6:05   ` Michael Tokarev
2010-04-08  6:09     ` Thomas Mueller
2010-04-08  6:23       ` Thomas Mueller
2010-04-08 10:08     ` Christoph Hellwig

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