Date: Tue, 08 May 2012 21:36:05 -0700 From: Sean Bruno <seanbru@yahoo-inc.com> To: John Baldwin <jhb@freebsd.org> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Jack Vogel <jfvogel@gmail.com> Subject: Re: igb(4) Pondering a bind to cpu patch Message-ID: <1336538165.28313.1.camel@powernoodle-l7> In-Reply-To: <1336084418.3077.21.camel@powernoodle-l7.corp.yahoo.com> References: <1335312667.11564.13.camel@powernoodle-l7.corp.yahoo.com> <201204250932.21378.jhb@freebsd.org> <1335382225.2722.6.camel@powernoodle-l7.corp.yahoo.com> <1336084418.3077.21.camel@powernoodle-l7.corp.yahoo.com>
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On Thu, 2012-05-03 at 15:33 -0700, Sean Bruno wrote: > > On Wed, 2012-04-25 at 12:30 -0700, Sean Bruno wrote: > > On Wed, 2012-04-25 at 06:32 -0700, John Baldwin wrote: > > > CPU IDs are not guaranteed to be dense. However, you can use > > > CPU_FIRST() and > > > CPU_NEXT() with your static global instead. > > > > > Ah, does CPU_NEXT() reset to 0 when it reaches the end of its list of > > CPUs? > > > > Ah, I see. So, yeah, here's a v2 of the patch that does "the right" > thing with non-sparse cpus, mulitple queues, and mulitple physical > interfaces. > > http://people.freebsd.org/~sbruno/if_igb.c.txt > > > > > > OTOH, if igb were to just leave the interrupts alone instead of > > > binding them > > > by hand, they would get round-robin assigned among available cores > > > already. I > > > think in this case the best approach might be to add a tunable to > > > disable > > > igb's manual binding and instead let the default system round-robin > > > be > > > preserved. > > > > also, yes. Why *are* we binding to CPUs in the first place? Are we > > afraid that the scheduler won't do the right thing and we're trying to > > work around some unknown performance issue ? > > > > Sean > > > > Still haven't seen a good reason to bind the queues by default in the > first place. > > Sean > If there's no objection, I'll commit this in the morning. Sean
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