From: Stefan Hajnoczi <stefanha@gmail.com>
To: Michael Baysek <mbaysek@liquidweb.com>
Cc: kvm@vger.kernel.org
Subject: Re: vhost-blk development
Date: Thu, 12 Apr 2012 09:30:30 +0100 [thread overview]
Message-ID: <CAJSP0QXiz8bqVh1UZ-tRhZHFP2cb3Bu7A7cBqhVw2LgG_CeQGw@mail.gmail.com> (raw)
In-Reply-To: <6815254.61554.1334163130932.JavaMail.root@zimbra.liquidweb.com>
On Wed, Apr 11, 2012 at 5:52 PM, Michael Baysek <mbaysek@liquidweb.com> wrote:
> I am purposefully not using O_DIRECT since most workloads will not be using
> it, although I did notice better performance when I did use it. I did
> already identify the page cache as a hinderance as well.
If you do not use O_DIRECT in the benchmark then you are not
exercising pure disk I/O and therefore the benchmark is not measuring
virtio-blk performance.
> I seem to have hit some performance ceilings inside of the kvm guests that
> are much lower than that of the host they are running on. I am seeing a
> lot more interrupts and context switches on the parent than I am in the
> guests, and I am looking for any and all ways to cut these down.
If you don't care about persistence of data I suggest doing the
ramdisk or tmpfs inside the guest. That way you keep all "storage"
operations inside the guest and avoid going through any storage
interface (virtio-blk, IDE, etc). You should be able to achieve
maximum performance using this approach although it does require guest
configuration.
Hope this helps,
Stefan
next prev parent reply other threads:[~2012-04-12 8:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-09 22:59 vhost-blk development Michael Baysek
2012-04-10 11:55 ` Stefan Hajnoczi
2012-04-10 17:25 ` Michael Baysek
2012-04-11 10:19 ` Stefan Hajnoczi
2012-04-11 16:52 ` Michael Baysek
2012-04-12 8:30 ` Stefan Hajnoczi [this message]
2012-04-13 5:38 ` Liu Yuan
2012-04-19 20:26 ` Michael Baysek
2012-04-20 4:28 ` Liu Yuan
2012-04-20 20:23 ` Michael Baysek
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