| Message ID | 4FF696C9.5070907@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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: 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. 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) >> 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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 07/08/2012 08:23 PM, Jason Wang wrote: > On 07/07/2012 12:23 AM, Rick Jones wrote: >> On 07/06/2012 12:42 AM, Jason Wang wrote: >> 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. When running aggregate netperfs, *something* has to be done to address the prospect of skew error. Otherwise the results are suspect. happy benchmarking, rick jones -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index c465d3e..166a888 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1567,7 +1567,7 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb) in_flight = tcp_packets_in_flight(tp); - BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight)); + BUG_ON(tp->snd_cwnd <= in_flight); send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;