linux-kernel - Re: fallout of 16K stacks

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Date:	Mon, 07 Jul 2014 15:49:48 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>, torvalds@...ux-foundation.org
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: fallout of 16K stacks

On 07/07/2014 03:30 PM, Andi Kleen wrote:
> 
> Since the 16K stack change I noticed a number of problems with
> my usual stress tests. They have a tendency to bomb out
> because something cannot fork.

As in ENOMEM or does something worse happen?

> - AIM7 on a dual socket socket system now cannot reliably run 
>> 1000 parallel jobs.

... with how much RAM?

> - LTP stress + memhog stress in parallel to something else
> usually doesn't survive the night.
> 
> Do we need to strengthen the memory allocator to try
> harder for 16K?

Can we even?  The probability of success goes down exponentially in the
order requested.  Movable pages can help, of course, but still, there is
a very real cost to this :(

	-hpa

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