Date: Sun, 3 Oct 2004 21:24:52 -0700
From: Paul Jackson <pj@sgi.com>
To: "Martin J. Bligh" <mbligh@aracnet.com>
Cc: pwil3058@bigpond.net.au, frankeh@watson.ibm.com, dipankar@in.ibm.com,
       akpm@osdl.org, ckrm-tech@lists.sourceforge.net, efocht@hpce.nec.com,
       lse-tech@lists.sourceforge.net, hch@infradead.org, steiner@sgi.com,
       jbarnes@sgi.com, sylvain.jeaugey@bull.net, djh@sgi.com,
       linux-kernel@vger.kernel.org, colpatch@us.ibm.com, Simon.Derr@bull.net,
       ak@suse.de, sivanich@sgi.com
Subject: Re: [Lse-tech] [PATCH] cpusets - big numa cpu and memory placement
Message-Id: <20041003212452.1a15a49a.pj@sgi.com>
In-Reply-To: <838090000.1096862199@[10.10.2.4]>
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Martin wrote:
> Then when I fork off exclusive subset for CPUs 1&2, I have to push A & B
> into it.

Tasks A & B must _not_ be considered members of that exclusive cpuset,
even though it seems that A & B must be attended to by the sched_domain
and memory_domain associated with that cpuset.

The workload managers expect to be able to list the tasks in a cpuset,
so it can hibernate, migrate, kill-off, or wait for the finish of these
tasks.  I've been through this bug before - it was one that cost Hawkes
a long week to debug - I was moving the per-cpu migration threads off
their home CPU because I didn't have a clear way to distinguish tasks
genuinely in a cpuset, from tasks that just happened to be indigenous to
some of the same CPUs.  My essential motivation for adapting a cpuset
implementation that has a task struct pointer to a shared cpuset struct
was to track exactly this relation - which tasks are in which cpuset.

No ... tasks A & B are not allowed in that new exclusive cpuset.

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