Date: Tue, 10 May 2005 00:13:27 -0700
From: Paul Jackson <pj@sgi.com>
To: Jim Nance <jlnance@sdf.lonestar.org>
Cc: davidsen@tmr.com, davej@redhat.com, willy@w.ods.org, akpm@osdl.org,
       jfbeam@bluetronic.net, nico-kernel@schottelius.org,
       linux-kernel@vger.kernel.org
Subject: Re: /proc/cpuinfo format - arch dependent!
Message-Id: <20050510001327.5197dd21.pj@sgi.com>
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	<427FA876.7000401@tmr.com>
	<20050510022301.GA13763@SDF.LONESTAR.ORG>
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Jim wrote:
> I see two problems with encouraging applications to get involved
> with processor selection.

I suspect you are confusing "application" with "not kernel".

There are basically three layers of software on big systems:

 1) kernel
 2) administration (system services, libraries and utilities)
 3) application

Something like a batch manager is an example in layer (2) that needs
extensive knowledge of a systems hardware, and extensive ability to
manage exactly what runs and allocates where.

Large systems very much expect to manage what threads run where. These
API's are already present - check out sched_setaffinity, mbind,
set_mempolicy, and cpusets.  The details of what hardware is where,
including memory, processor and interconnect, are also there as well, in
various /proc and /sys files.

No - we don't expect the application to know all this.  But we absolutely
require that various admin level programs know this stuff in intimate
detail, and enable the administration of large systems in a variety of
ways.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@engr.sgi.com> 1.650.933.1373, 1.925.600.0401
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