Date: Sun, 11 May 2014 12:31:14 +0400 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Adrian Chadd <adrian@FreeBSD.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r265792 - head/sys/kern Message-ID: <20140511083114.GA53503@zxy.spb.ru> In-Reply-To: <201405100053.s4A0rbF9080571@svn.freebsd.org> References: <201405100053.s4A0rbF9080571@svn.freebsd.org>
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On Sat, May 10, 2014 at 12:53:37AM +0000, Adrian Chadd wrote: > Author: adrian > Date: Sat May 10 00:53:36 2014 > New Revision: 265792 > URL: http://svnweb.freebsd.org/changeset/base/265792 > > Log: > Add in support to optionally pin the swi threads. > > Under enough load, the swi's can actually be preempted and migrated > to other currently free cores. When doing RSS experiments, this lead > to the per-CPU TCP timers not lining up any more with the RX CPU said > flows were ending up on, leading to increased lock contention. > > Since there was a little pushback on flipping them on by default, > I've left the default at "don't pin." > > The other less obvious problem here is that the default swi > is also the same as the destination swi for CPU #0. So if one > pins the swi on CPU #0, there's no default floating swi. > > A nice future project would be to create a separate swi for > the "default" floating swi, as well as per-CPU swis that are > (optionally) pinned. MFC planed? I have 10.0 box with aprox. 16Gbit TCP at peak.
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