Date: Thu, 03 May 2012 15:33:38 -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: <1336084418.3077.21.camel@powernoodle-l7.corp.yahoo.com> In-Reply-To: <1335382225.2722.6.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>
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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
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