From owner-freebsd-net@FreeBSD.ORG  Wed Apr 25 19:30:39 2012
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From: Sean Bruno <seanbru@yahoo-inc.com>
To: John Baldwin <jhb@freebsd.org>
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Date: Wed, 25 Apr 2012 12:30:25 -0700
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Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>,
	Jack Vogel <jfvogel@gmail.com>
Subject: Re: igb(4) Pondering a bind to cpu patch
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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?


> 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