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Date: Mon, 9 Nov 2015 02:39:24 +0000 From: Dexuan Cui <decui@...rosoft.com> To: Eric Dumazet <eric.dumazet@...il.com>, David Ahern <dsa@...ulusnetworks.com>, Simon Xiao <sixiao@...rosoft.com> CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>, Haiyang Zhang <haiyangz@...rosoft.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>, David Miller <davem@...emloft.net> Subject: RE: linux-next network throughput performance regression > From: devel [mailto:driverdev-devel-bounces@...uxdriverproject.org] On Behalf > Of Eric Dumazet > Sent: Sunday, November 8, 2015 3:36 > To: David Ahern <dsa@...ulusnetworks.com> > Cc: netdev@...r.kernel.org; Haiyang Zhang <haiyangz@...rosoft.com>; linux- > kernel@...r.kernel.org; devel@...uxdriverproject.org; David Miller > <davem@...emloft.net> > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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