On 07/07/2012 12:23 AM, Rick Jones wrote:
On 07/06/2012 12:42 AM, Jason Wang wrote:
I'm not expert of tcp, but looks like the changes are reasonable:
- we can do full-sized TSO check in tcp_tso_should_defer() only for
westwood, according to tcp westwood
- run tcp_tso_should_defer for tso_segs = 1 when tso is enabled.
I'm sure Eric and David will weigh-in on the TCP change. My initial
inclination would have been to say "well, if multiqueue is draining
faster, that means ACKs come-back faster, which means the "race"
between more data being queued by netperf and ACKs will go more to the
ACKs which means the segments being sent will be smaller - as
TCP_NODELAY is not set, the Nagle algorithm is in force, which means
once there is data outstanding on the connection, no more will be sent
until either the outstanding data is ACKed, or there is an
accumulation of > MSS worth of data to send.
Also, how are you combining the concurrent netperf results? Are you
taking sums of what netperf reports, or are you gathering statistics
outside of netperf?
The throughput were just sumed from netperf result like what netperf
manual suggests. The cpu utilization were measured by mpstat.
Which mechanism to address skew error? The netperf manual describes
more than one:
This mechanism is missed in my test, I would add them to my test scripts.
http://www.netperf.org/svn/netperf2/trunk/doc/netperf.html#Using-Netperf-to-Measure-Aggregate-Performance
Personally, my preference these days is to use the "demo mode" method
of aggregate results as it can be rather faster than (ab)using the
confidence intervals mechanism, which I suspect may not really scale
all that well to large numbers of concurrent netperfs.
During my test, the confidence interval would even hard to achieved in
RR test when I pin vhost/vcpus in the processors, so I didn't use it.
I also tend to use the --enable-burst configure option to allow me to
minimize the number of concurrent netperfs in the first place. Set
TCP_NODELAY (the test-specific -D option) and then have several
transactions outstanding at one time (test-specific -b option with a
number of additional in-flight transactions).
This is expressed in the runemomniaggdemo.sh script:
http://www.netperf.org/svn/netperf2/trunk/doc/examples/runemomniaggdemo.sh
which uses the find_max_burst.sh script:
http://www.netperf.org/svn/netperf2/trunk/doc/examples/find_max_burst.sh
to pick the burst size to use in the concurrent netperfs, the results
of which can be post-processed with:
http://www.netperf.org/svn/netperf2/trunk/doc/examples/post_proc.py
The nice feature of using the "demo mode" mechanism is when it is
coupled with systems with reasonably synchronized clocks (eg NTP) it
can be used for many-to-many testing in addition to one-to-many
testing (which cannot be dealt with by the confidence interval method
of dealing with skew error)
Yes, looks "demo mode" is helpful. I would have a look at these scripts,
Thanks.
A single instance TCP_RR test would help confirm/refute any
non-trivial change in (effective) path length between the two cases.
Yes, I would test this thanks.
Excellent.
happy benchmarking,
rick jones
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