[rhelv6-list] Setting overcommit_memory=2 kills system

[Michael Coffman]

On Thu, May 17, 2012 at 2:17 PM, Brian Long (brilong) <brilong at cisco.com>wrote:

> On May 17, 2012, at 3:08 PM, Michael Coffman wrote:
> > In general I am in the habit of turning off memory overcommit because I
> believe it's a bad thing in a multi-user environment.   This was never a
> problem on rhel5 systems, but on rhel6, I am having issues.    When I try
> to set overcommit_memory=2, my system locks up.   It basically behaves as
> if the memory is all used up...   I see the same behavior on centos6 or
> rhel6.
> [snip]
> > One last point.   If I set the overcommit values in /etc/sysctl.conf and
> then reboot, the values get set correctly on boot and everything seems
> fine.   In addition I can then change the value of overcommit_memory to 0
> and back to 2 with out any ill affects.
>
> Just to clarify, if you set this in sysctl.conf and reboot, you're fine.
>  It's only if you try setting this on-the-fly that the system borks.
>
>
Yes, that's correct.


> If this is true, it sounds like you don't have a problem for production
> systems.  You set up /etc/sysctl.conf in your kickstart and never worry
> about it, right?
>
>
Sort of...


> Are you just curious on why you cannot do this on-the-fly?
>
>
I ran into this because my post install runs cfengine to configure things
and when it got to the shellcommand section and ran sysctl -p, everything
stopped.

As I said, once set it seems to be OK.  But I would hate to make changes to
my global sysctl.conf later on,  then have cfengine
run an update and watch my machines lock up.



> /Brian/




-- 
-MichaelC
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