linux-kernel - Re: fallout of 16K stacks

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Date:	Tue, 8 Jul 2014 01:04:59 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>, torvalds@...ux-foundation.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: fallout of 16K stacks

On Mon, Jul 07, 2014 at 03:49:48PM -0700, H. Peter Anvin wrote:
> 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?

EAGAIN, then the workload stops. For an overnight stress
test that's pretty catastrophic. It may have killed some stuff
with the OOM killer too.

> > - AIM7 on a dual socket socket system now cannot reliably run 
> >> 1000 parallel jobs.
> 
> ... with how much RAM?

This system has 32G

> > - 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 :(

I hope so. In the worst case just try longer.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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