From: "Michael S. Tsirkin" <mst@redhat.com>
To: Shirley Ma <mashirle@us.ibm.com>
Cc: Steve Dobbelstein <steved@us.ibm.com>, kvm@vger.kernel.org
Subject: Re: Network performance with small packets
Date: Thu, 27 Jan 2011 21:00:31 +0200 [thread overview]
Message-ID: <20110127190031.GC5228@redhat.com> (raw)
In-Reply-To: <1296153874.1640.27.camel@localhost.localdomain>
On Thu, Jan 27, 2011 at 10:44:34AM -0800, Shirley Ma wrote:
> On Wed, 2011-01-26 at 17:17 +0200, Michael S. Tsirkin wrote:
> > I am seeing a similar problem, and am trying to fix that.
> > My current theory is that this is a variant of a receive livelock:
> > if the application isn't fast enough to process
> > incoming data, the guest net stack switches
> > from prequeue to backlog handling.
> >
> > One thing I noticed is that locking the vhost thread
> > and the vcpu to the same physical CPU almost doubles the
> > bandwidth. Can you confirm that in your setup?
> >
> > My current guess is that when we lock both to
> > a single CPU, netperf in guest gets scheduled
> > slowing down the vhost thread in the host.
> >
> > I also noticed that this specific workload
> > performs better with vhost off: presumably
> > we are loading the guest less.
>
> I found similar issue for small message size TCP_STREAM test when guest
> as TX. I found when I slow down TX, the BW performance will be doubled
> for 1K to 4K message size.
>
> Shirley
Interesting. In particular running vhost and the transmitting guest
on the same host would have the effect of slowing down TX.
Does it double the BW for you too?
--
MST
next prev parent reply other threads:[~2011-01-27 19:00 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-25 21:09 Network performance with small packets Steve Dobbelstein
2011-01-26 15:17 ` Michael S. Tsirkin
2011-01-27 18:44 ` Shirley Ma
2011-01-27 19:00 ` Michael S. Tsirkin [this message]
2011-01-27 19:09 ` Shirley Ma
2011-01-27 19:31 ` Michael S. Tsirkin
2011-01-27 19:45 ` Shirley Ma
2011-01-27 20:05 ` Michael S. Tsirkin
2011-01-27 20:15 ` Shirley Ma
2011-01-28 18:29 ` Steve Dobbelstein
2011-01-28 22:51 ` Steve Dobbelstein
2011-02-01 15:52 ` [PATCHv2 dontapply] vhost-net tx tuning Michael S. Tsirkin
2011-02-01 23:07 ` Sridhar Samudrala
2011-02-01 23:27 ` Shirley Ma
2011-02-02 4:36 ` Michael S. Tsirkin
2011-01-27 21:02 ` Network performance with small packets David Miller
2011-01-27 21:30 ` Shirley Ma
2011-01-28 12:16 ` Michael S. Tsirkin
2011-02-01 0:24 ` Steve Dobbelstein
2011-02-01 1:30 ` Sridhar Samudrala
2011-02-01 5:56 ` Michael S. Tsirkin
2011-02-01 21:09 ` Shirley Ma
2011-02-01 21:24 ` Michael S. Tsirkin
2011-02-01 21:32 ` Shirley Ma
2011-02-01 21:42 ` Michael S. Tsirkin
2011-02-01 21:53 ` Shirley Ma
2011-02-01 21:56 ` Michael S. Tsirkin
2011-02-01 22:59 ` Shirley Ma
2011-02-02 4:40 ` Michael S. Tsirkin
2011-02-02 6:05 ` Shirley Ma
2011-02-02 6:19 ` Shirley Ma
2011-02-02 6:29 ` Michael S. Tsirkin
2011-02-02 7:14 ` Shirley Ma
2011-02-02 7:33 ` Shirley Ma
2011-02-02 10:49 ` Michael S. Tsirkin
2011-02-02 15:42 ` Shirley Ma
2011-02-02 15:48 ` Michael S. Tsirkin
2011-02-02 17:12 ` Shirley Ma
2011-02-02 18:20 ` Michael S. Tsirkin
2011-02-02 18:26 ` Shirley Ma
2011-02-02 10:48 ` Michael S. Tsirkin
2011-02-02 6:34 ` Krishna Kumar2
2011-02-02 7:03 ` Shirley Ma
2011-02-02 7:37 ` Krishna Kumar2
2011-02-02 10:48 ` Michael S. Tsirkin
2011-02-02 15:39 ` Shirley Ma
2011-02-02 15:47 ` Michael S. Tsirkin
2011-02-02 17:10 ` Shirley Ma
2011-02-02 17:32 ` Michael S. Tsirkin
2011-02-02 18:11 ` Shirley Ma
2011-02-02 18:27 ` Michael S. Tsirkin
2011-02-02 19:29 ` Shirley Ma
2011-02-02 20:17 ` Michael S. Tsirkin
2011-02-02 21:03 ` Shirley Ma
2011-02-02 21:20 ` Michael S. Tsirkin
2011-02-02 21:41 ` Shirley Ma
2011-02-03 5:59 ` Michael S. Tsirkin
2011-02-03 6:09 ` Shirley Ma
2011-02-03 6:16 ` Michael S. Tsirkin
2011-02-03 5:05 ` Shirley Ma
2011-02-03 6:13 ` Michael S. Tsirkin
2011-02-03 15:58 ` Shirley Ma
2011-02-03 16:20 ` Michael S. Tsirkin
2011-02-03 17:18 ` Shirley Ma
2011-02-01 5:54 ` Michael S. Tsirkin
2011-02-01 17:23 ` Michael S. Tsirkin
[not found] ` <1296590943.26937.797.camel@localhost.localdomain>
[not found] ` <20110201201715.GA30050@redhat.com>
2011-02-01 20:25 ` Shirley Ma
2011-02-01 21:21 ` Michael S. Tsirkin
2011-02-01 21:28 ` Shirley Ma
2011-02-01 21:41 ` Michael S. Tsirkin
2011-02-02 4:39 ` Krishna Kumar2
2011-02-02 4:42 ` Michael S. Tsirkin
2011-02-09 0:37 ` Rusty Russell
2011-02-09 0:53 ` Michael S. Tsirkin
2011-02-09 1:39 ` Rusty Russell
2011-02-09 1:55 ` Michael S. Tsirkin
2011-02-09 7:43 ` Stefan Hajnoczi
2011-03-08 21:57 ` Shirley Ma
2011-03-09 2:21 ` Andrew Theurer
2011-03-09 15:42 ` Shirley Ma
2011-03-10 1:49 ` Rusty Russell
2011-04-12 20:01 ` Michael S. Tsirkin
2011-04-14 11:28 ` Rusty Russell
2011-04-14 12:40 ` Michael S. Tsirkin
2011-04-14 16:03 ` Michael S. Tsirkin
2011-04-19 0:33 ` Rusty Russell
2011-02-02 18:38 ` Michael S. Tsirkin
2011-02-02 19:15 ` Steve Dobbelstein
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