netdev - Re: Flow Control and Port Mirroring Revisited

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Date:	Wed, 19 Jan 2011 18:11:36 +0900
From:	Simon Horman <horms@...ge.net.au>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Rick Jones <rick.jones2@...com>, Jesse Gross <jesse@...ira.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.linux-foundation.org, dev@...nvswitch.org,
	virtualization@...ts.osdl.org, netdev@...r.kernel.org,
	kvm@...r.kernel.org
Subject: Re: Flow Control and Port Mirroring Revisited

On Tue, Jan 18, 2011 at 10:13:33PM +0200, Michael S. Tsirkin wrote:
> On Tue, Jan 18, 2011 at 11:41:22AM -0800, Rick Jones wrote:
> > >So it won't be all that simple to implement well, and before we try,
> > >I'd like to know whether there are applications that are helped
> > >by it. For example, we could try to measure latency at various
> > >pps and see whether the backpressure helps. netperf has -b, -w
> > >flags which might help these measurements.
> > 
> > Those options are enabled when one adds --enable-burst to the
> > pre-compilation ./configure  of netperf (one doesn't have to
> > recompile netserver).  However, if one is also looking at latency
> > statistics via the -j option in the top-of-trunk, or simply at the
> > histogram with --enable-histogram on the ./configure and a verbosity
> > level of 2 (global -v 2) then one wants the very top of trunk
> > netperf from:
> > 
> > http://www.netperf.org/svn/netperf2/trunk
> > 
> > to get the recently added support for accurate (netperf level) RTT
> > measuremnts on burst-mode request/response tests.
> > 
> > happy benchmarking,
> > 
> > rick jones

Thanks Rick, that is really helpful.

> > PS - the enhanced latency statistics from -j are only available in
> > the "omni" version of the TCP_RR test.  To get that add a
> > --enable-omni to the ./configure - and in this case both netperf and
> > netserver have to be recompiled.
> 
> 
> Is this TCP only? I would love to get latency data from UDP as well.

At a glance, -- -T UDP is what you are after.
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