From owner-freebsd-questions  Tue Jun 22 18:11:47 1999
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	Tue, 22 Jun 1999 18:11:39 -0700
To: freebsd-questions@FreeBSD.ORG, freebsd-smp@FreeBSD.ORG
Subject: Re: Multi processor support?
References: <199906221835.LAA25521@usr05.primenet.com>
From: Arun Sharma <adsharma@home.com>
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Date: 22 Jun 1999 18:11:39 -0700
In-Reply-To: Terry Lambert's message of "Tue, 22 Jun 1999 18:35:27 +0000 (GMT)"
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Terry Lambert <tlambert@primenet.com> writes:

> The best you are going to get is explicit division of tasks
> between multiple processes.  At *that* point (and *only* then)
> does CPU affinity become a real issue.  Even so, it's not an
> issue addressed (IMO) by the Linux SMP implementation (any
> more than the FreeBSD or BSDI implementations).

Linux scheduler does implement processor affinity to some extent:

#ifdef __SMP__
	/* Give a largish advantage to the same processor...   */
	/* (this is equivalent to penalizing other processors) */
	if (p->processor == this_cpu)
		weight += PROC_CHANGE_PENALTY;
#endif

A better way to do this would be to split the runnable process queues
into per processor queues (ref: Digital's SMP implementation).

Also, the ability to have multiple threads executing in a single
address space, scheduled on different processors simultaneously is
very significant.

	-Arun


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