linux-kernel - Re: [RFC 5/8] Make writeout during reclaim cpuset aware

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Message-Id: <20070116203622.7f1b4e87.pj@sgi.com>
Date:	Tue, 16 Jan 2007 20:36:22 -0800
From:	Paul Jackson <pj@....com>
To:	Andi Kleen <ak@...e.de>
Cc:	clameter@....com, akpm@...l.org, menage@...gle.com,
	linux-kernel@...r.kernel.org, nickpiggin@...oo.com.au,
	linux-mm@...ck.org, dgc@....com
Subject: Re: [RFC 5/8] Make writeout during reclaim cpuset aware

> With a per node dirty limit ...

What would this mean?

Lets say we have a simple machine with 4 nodes, cpusets disabled.

Lets say all tasks are allowed to use all nodes, no set_mempolicy
either.

If a task happens to fill up 80% of one node with dirty pages, but
we have no dirty pages yet on other nodes, and we have a dirty ratio
of 40%, then do we throttle that task's writes?

I am surprised you are asking for this, Andi.  I would have thought
that on no-cpuset systems, the system wide throttling served your
needs fine.  If not, then I can only guess that is because NUMA
mempolicy constraints on allowed nodes are causing the same dirty page
problems as cpuset constrained systems -- is that your concern?

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