> From: devel [mailto:driverdev-devel-bounces@xxxxxxxxxxxxxxxxxxxxxx] On Behalf > Of Eric Dumazet > Sent: Sunday, November 8, 2015 3:36 > To: David Ahern <dsa@xxxxxxxxxxxxxxxxxxx> > Cc: netdev@xxxxxxxxxxxxxxx; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; linux- > kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; David Miller > <davem@xxxxxxxxxxxxx> > Subject: Re: linux-next network throughput performance regression > > On Fri, 2015-11-06 at 14:30 -0700, David Ahern wrote: > > On 11/6/15 2:18 PM, Simon Xiao wrote: > > > The .config file used to build linux-next kernel is attached to this mail. > > > > Thanks. > > > > Failed to notice this on the first response; my brain filled in. Why > > linux-next tree? Can you try net-next which is more relevant for this > > mailing list, post the top commit id and config file used? > > Throughput on a single TCP flow for a 40G NIC can be tricky to tune. Why is a single TCP flow trickier than multiple TCP flows? IMO it should be easier to analyze the issue of a single TCP flow? Here the perf drop in Simon's test is very obvious -- 50%, but it looks Eric can't reproduce it, so I suppose some net-related kernel config options may do the magic? Maybe Simon can narrow the regression down by bisecting. :-) > Make sure IRQ are properly setup/balanced, as I know that IRQ names were > changed recently and your scripts might have not noticed... > > Also "ethtool -c eth0" might show very different interrupt coalescing > params ? > > I too have a Mellanox 40Gb in my lab and saw no difference in > performance with recent kernels. > > Of course, a simple "perf record -a -g sleep 4 ; perf report" might > point to some obvious issue. Like unexpected segmentation in case of > forwarding... > Thanks, -- Dexuan _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
