linux-kernel - Re: [13/18] x86_64: Allow fallback for the stack

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Date:	Thu, 4 Oct 2007 14:20:19 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Rik van Riel <riel@...hat.com>
cc:	Andi Kleen <ak@...e.de>, akpm@...ux-foundation.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, travis@....com
Subject: Re: [13/18] x86_64: Allow fallback for the stack

On Thu, 4 Oct 2007, Rik van Riel wrote:

> > Well we can now address the rarity. That is the whole point of the 
> > patchset.
> 
> Introducing complexity to fight a very rare problem with a good
> fallback (refusing to fork more tasks, as well as lumpy reclaim)
> somehow does not seem like a good tradeoff.

The problem can become non-rare on special low memory machines doing wild 
swapping things though.

> > It will be more common if the stack size is increased beyond 8k.
> 
> Why would we want to do such a thing?

Because NUMA requires more stack space. In particular support for very 
large cpu configurations of 16k may require 2k cpumasks on the stack.

> 8kB stacks are large enough...

For many things yes. I just want to have the compile time option to 
increase it.
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