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Date: Wed, 6 Jun 2007 16:11:03 -0700
From: Randy Dunlap <randy.dunlap@oracle.com>
To: Justin Piszcz <jpiszcz@lucidpixels.com>
Cc: Jesse Barnes <jesse.barnes@intel.com>, Andi Kleen <andi@firstfloor.org>,
       linux-kernel@vger.kernel.org,
       "Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH] trim memory not covered by WB MTRRs
Message-Id: <20070606161103.f8e3b253.randy.dunlap@oracle.com>
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On Wed, 6 Jun 2007 18:54:37 -0400 (EDT) Justin Piszcz wrote:

> Hm, not sure if it was from the patch or what but I ran this:
> 
> 1. swapoff -a
> 2. ./eatmem
> 
> The machine responded to ping and alt-sysrq-b but the box remain 
> unresponsive, I guess the kernel did not kill the process? :(
> 
> The moments before it 'froze'
> 
> top - 18:48:01 up 15 min,  7 users,  load average: 6.61, 18.50, 13.31
> Tasks: 200 total,  18 running, 182 sleeping,   0 stopped,   0 zombie
> Cpu(s):  0.0%us, 90.7%sy,  0.0%ni,  5.9%id,  3.3%wa,  0.0%hi,  0.0%si, 
> 0.0%st
> Mem:   8039576k total,  7998860k used,    40716k free,        8k buffers
> Swap:        0k total,        0k used,        0k free,     1664k cached
> 
>    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>    248 root      11  -5     0    0    0 R   85  0.0   0:16.05 kswapd0
>   2265 nut       18   0 13320  244    4 R   40  0.0   0:03.13 newhidups
>   2267 nut       18   0 12216  168    4 R   40  0.0   0:02.04 upsd
>   2474 ntp       18   0 22192  400    8 R   39  0.0   0:02.00 ntpd
>   3563 jpiszcz   18   0 41964 1264    4 R   38  0.0   0:02.20 pine
>   3530 root      18   0 96240 3132   36 R   37  0.0   0:02.09 kdm_greet
>   2052 root      18   0  6080  112    4 R   37  0.0   0:02.00 hald-addon-stor
>   4479 war       17   0 18012  700  252 R   33  0.0   0:01.81 top
>   4480 war       19   0 6948m 6.8g    4 R   22 88.4   0:05.81 eatmem
>   2095 root      18   0 13128  216    8 R   10  0.0   0:00.50 dirmngr
>   2545 root      18   0 95788 2488    4 R    5  0.0   0:00.25 apache2
>   3564 war       18   0 41620  832    4 R    5  0.0   0:00.34 pine
>   2270 nut       15   0 12212  144    4 S    1  0.0   0:00.05 upsmon
>    561 root      10  -5     0    0    0 S    0  0.0   0:00.02 xfsbufd
> 
> Very simply program:
> 
> #include <iostream>
> using namespace std;
> 
> int main()
> {
>    long int interations = 10000000;
>    int counter = 1;
> 
>    for(counter;counter<interations;counter++)
>    {
>       double *d = new double[100];

You usually have to access the allocated memory, like:

	*d = 1.0;

for it to actually be allocated (AFAIK).

>    }
> 
>    return 0;
> }
> 
> Any idea why the OOM killer can or does not kill it?

What are the values of /proc/sys/vm/overcommit* ?

See Documentation/vm/overcommit-accounting .

---
~Randy
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