From: "Michael S. Tsirkin" <mst@redhat.com>
To: Shirley Ma <mashirle@us.ibm.com>
Cc: Krishna Kumar2 <krkumar2@in.ibm.com>,
David Miller <davem@davemloft.net>,
kvm@vger.kernel.org, mashirle@linux.vnet.ibm.com,
netdev@vger.kernel.org, netdev-owner@vger.kernel.org,
Sridhar Samudrala <sri@us.ibm.com>,
Steve Dobbelstein <steved@us.ibm.com>
Subject: Re: Network performance with small packets
Date: Wed, 2 Feb 2011 22:17:31 +0200 [thread overview]
Message-ID: <20110202201731.GB15150@redhat.com> (raw)
In-Reply-To: <1296674975.25430.59.camel@localhost.localdomain>
On Wed, Feb 02, 2011 at 11:29:35AM -0800, Shirley Ma wrote:
> On Wed, 2011-02-02 at 20:27 +0200, Michael S. Tsirkin wrote:
> > On Wed, Feb 02, 2011 at 10:11:51AM -0800, Shirley Ma wrote:
> > > On Wed, 2011-02-02 at 19:32 +0200, Michael S. Tsirkin wrote:
> > > > OK, but this should have no effect with a vhost patch
> > > > which should ensure that we don't get an interrupt
> > > > until the queue is at least half empty.
> > > > Right?
> > >
> > > There should be some coordination between guest and vhost.
> >
> > What kind of coordination? With a patched vhost, and a full ring.
> > you should get an interrupt per 100 packets.
> > Is this what you see? And if yes, isn't the guest patch
> > doing nothing then?
>
> vhost_signal won't be able send any TX interrupts to guest when guest TX
> interrupt is disabled. Guest TX interrupt is only enabled when running
> out of descriptors.
Well, this is also the only case where the queue is stopped, no?
> > > We shouldn't
> > > count the TX packets when netif queue is enabled since next guest TX
> > > xmit will free any used buffers in vhost. We need to be careful here
> > in
> > > case we miss the interrupts when netif queue has stopped.
> > >
> > > However we can't change old guest so we can test the patches
> > separately
> > > for guest only, vhost only, and the combination.
> > >
> > > > > >
> > > > > > Yes, it seems unrelated to tx interrupts.
> > > > >
> > > > > The issue is more likely related to latency.
> > > >
> > > > Could be. Why do you think so?
> > >
> > > Since I played with latency hack, I can see performance difference
> > for
> > > different latency.
> >
> > Which hack was that?
>
> I tried to accumulate multiple guest to host notifications for TX xmits,
> it did help multiple streams TCP_RR results;
I don't see a point to delay used idx update, do you?
So delaying just signal seems better, right?
> I also forced vhost
> handle_tx to handle more packets; both hack seemed help.
>
> Thanks
> Shirley
Haven't noticed that part, how does your patch make it
handle more packets?
--
MST
next prev parent reply other threads:[~2011-02-02 20:18 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
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 [this message]
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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