[CentOS] Setting overcommit_memory=2 kills system

Fri May 18 16:24:10 UTC 2012
Michael Coffman <michael.coffman at avagotech.com>

On Fri, May 18, 2012 at 7:50 AM, Les Mikesell <lesmikesell at gmail.com> wrote:

> On Fri, May 18, 2012 at 8:46 AM, Michael Coffman
> <michael.coffman at avagotech.com> wrote:
> >
> >> Just because one machine fails gracefully does not mean the next will.
> >>
> >
> > I don't even know what the above means.
> >
> >
> >> But really buy some ram for real. OR solve the real problem.
> >>
> >>
> >
> > Well that's just ridiculous.  'Real problem'?.    If I run a command to
> > change a kernel value, I assume that my system will not be rendered
> useless
> > because it now believes all the memory is consumed.   It seems like a
> > problem to me no matter how much memory the machine has.
>
> If you are already overcommitted, what do you expect to happen when
> you say not to allow that?   The kernel doesn't have a really good way
> to handle that situation (or any other OOM condition for that
> matter...).
>
>
OK.  So I was confused because free shows I have plenty of memory and I am
only now noticing that Committed_AS shows a very large value.   This is
largely an idle system:

             total       used       free     shared    buffers     cached
Mem:       2052176     951648    1100528          0     147580     626096
-/+ buffers/cache:     177972    1874204
Swap:      2052088          0    2052088

So my real question should have been why would the Committed_AS value be so
large?
Committed_AS:   137197248820 kB

On the exact same hardware with fresh build of centos5u4 and overcommit
turned on:
Committed_AS:   125716 kB



 --
>   Les Mikesell
>     lesmikesell at gmail.com
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-- 
-MichaelC