Date: Sun, 3 Apr 2005 17:24:13 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Paul Jackson <pj@engr.sgi.com>
Cc: kenneth.w.chen@intel.com, torvalds@osdl.org, nickpiggin@yahoo.com.au,
       akpm@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: [patch] sched: auto-tune migration costs [was: Re: Industry db benchmark result on recent 2.6 kernels]
Message-ID: <20050403152413.GA26631@elte.hu>
References: <200504020100.j3210fg04870@unix-os.sc.intel.com> <20050402145351.GA11601@elte.hu> <20050402215332.79ff56cc.pj@engr.sgi.com> <20050403070415.GA18893@elte.hu> <20050403043420.212290a8.pj@engr.sgi.com> <20050403071227.666ac33d.pj@engr.sgi.com>
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* Paul Jackson <pj@engr.sgi.com> wrote:

> 
>  3) I was noticing that my test system was only showing a couple of 
>     distinct values for cpu_distance, even though it has 4 distinct 
>     distances for values of node_distance.  So I coded up a variant of 
>     cpu_distance that converts the problem to a node_distance problem, 
>     and got the following cost matrix:

>     The code (below) is twice as complicated, the runtime twice as long,
>     and it's less intuitive - sched_domains seems more appropriate as
>     the basis for migration costs than the node distances in SLIT tables.
>     Finally, I don't know if distinguishing between costs of 21.7 and
>     25.3 is worth much.

the main problem is that we can do nothing with this matrix: we only 
print it, but then the values get written into a 0/1 sched-domains 
hierarchy - so the information is lost.

if you create a sched-domains hierarchy (based on the SLIT tables, or in 
whatever other way) that matches the CPU hierarchy then you'll 
automatically get the proper distances detected.

	Ingo
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