linux-kernel - Re: Bug#695182: [RFC] Reproducible OOM with just a few sleeps

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Message-Id: <201301312306.r0VN6tBx012280@como.maths.usyd.edu.au>
Date:	Fri, 1 Feb 2013 10:06:55 +1100
From:	paul.szabo@...ney.edu.au
To:	695182@...s.debian.org, ben@...adent.org.uk
Cc:	dave@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, pavel@....cz
Subject: Re: Bug#695182: [RFC] Reproducible OOM with just a few sleeps

Dear Ben,

> Based on your experience I might propose to change the automatic kernel
> selection for i386 so that we use 'amd64' on a system with >16GB RAM and
> a capable processor.

Don't you mean change to amd64 for >4GB (or any RAM), never using PAE?
PAE is broken for any amount of RAM. More precisely, PAE with any RAM
fails the "sleep test":
  n=0; while [ $n -lt 33000 ]; do sleep 600 & ((n=n+1)); done
and with >32GB fails the "write test":
  n=0; while [ $n -lt 99 ]; do dd bs=1M count=1024 if=/dev/zero of=x$n; ((n=n+1)); done
Why do you think 16GB is significant?

Thanks, Paul

Paul Szabo   psz@...hs.usyd.edu.au   http://www.maths.usyd.edu.au/u/psz/
School of Mathematics and Statistics   University of Sydney    Australia
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