On Fri, May 18, 2012 at 10:39 AM, Les Mikesell lesmikesell@gmail.comwrote:
On Fri, May 18, 2012 at 11:24 AM, Michael Coffman michael.coffman@avagotech.com wrote:
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 cachedMem: 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
I think that means an application has malloc()'d but not actually used a huge amount of memory. It used to be a common practice to test the amount of memory available by requesting more until the request failed, so it could be meaningless. If overcommit is turned off the app gets an error when it expects and backs off. The Committed_AS is an estimate of how much RAM/swap you would be likely to need if the requested storage is actually used.
Hmm. I replied and included a PS listing and go the following error:
Symantec Mail Security detected prohibited content in a message sent from your address (SYM:13316346581192243434)
My reply -
I get how overcommit works and it's affect on malloc. I intentionally turn it off so malloc will return a correct value when a process can't get enough memory. What I currently don't understand is the large value of Committed_AS on my centos6/rhel6 systems.
I just did a fresh build of centos6u2 and there is very little running and the value is: Committed_AS: 136382202700 kB
There is almost nothing running.... Filtering out kernel processes here is the list of running processes
See attached ps listing if interested...
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Les Mikesell lesmikesell@gmail.com _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos