Date: Wed, 25 Apr 2012 15:43:08 -0400 From: John Baldwin <jhb@freebsd.org> To: Sean Bruno <seanbru@yahoo-inc.com> 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: <201204251543.09099.jhb@freebsd.org> 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>
next in thread | previous in thread | raw e-mail | index | archive | help
On Wednesday, April 25, 2012 3:30:25 pm 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? Yes. > > 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 ? Well, in some cases you want to know exactly which CPUs are being used as you might bind other resources associated with the queue to those specific CPUs as well. -- John Baldwin
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201204251543.09099.jhb>