linux-kernel - Re: linux thread scheduling

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Message-Id: <201202102344.12509.marogge@onlinehome.de>
Date:	Fri, 10 Feb 2012 23:44:12 +0100
From:	Martin Rogge <marogge@...inehome.de>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: linux thread scheduling

Xin Tong wrote:

> I have a program that spawns 3 threads and there is a great deal of
> sharing among the three threads. they all read/update a couple of
> shared variables.
> 
> I run this on nehalem (8 cores, 4 core in each physical package),  I
> find that running the 3 threads on core 0, 1, 2 (using
> pthread_setaffinitiy) gives much better results, this is because the
> cache coherency protocol performs much better on the same package.
> However, if  I leave Linux (Suse Enterprise) to schedule it. it gives
> much worse performance, i suspect that linux is scheduling the 3
> threads across the physical packages ( 2 on one package, 1 on
> another). Is this possible ? why does linux do this ?

the following paper on cpu schedulers was posted recently. Maybe it gives you 
a starting point.

http://research.cs.wisc.edu/wind/Publications/meehean-thesis11.html
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