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:

quoted

quoted

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.

quoted

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.