linux-kernel - Re: Possible Bug in VM accounting (Committed_AS) on x86

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Date:	Wed, 29 Nov 2006 21:04:08 +0000
From:	Alan <alan@...rguk.ukuu.org.uk>
To:	"Kunal Trivedi" <ktrivedi@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Possible Bug in VM accounting (Committed_AS) on x86_64
 architecture ?

> I have noticed that 64 bit machine with overcommit policy (as above)
> starts giving problem within 3-4 weeks. To prove that I've written
> small program.

The older RHEL kernels had some cases that didn't quite account exactly
but current ones ought to be right - for Centos I'd expect similar but
ask there not here as it is a very old and branched away kernel.

>  It allocates memory of different sizes (not that it matters much due
> to caching of diffeent malloc. I am using standard ptmalloc). Sizes
> are 16B, 32B, 64B, 256B, 1024B, 57B, 127B and so on... . Then it
> touches that memory (memset) and then free it. These operations are
> being performed in while(1) loop.

I would expect that, it's fragmentation. The real test is whether the
values go back properly when you kill the program.
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