Running with vm.overcommit_memory=2

Barry K. Nathan barryn at
Fri Feb 18 19:23:28 UTC 2005

On Fri, Feb 18, 2005 at 07:13:55PM +0100, Ralf Ertzinger wrote:
> Is the amount of memory that 'free' reports as 'free' (or /proc/meminfo
> states as 'MemFree:') the amount of unrequested memory, or does it include
> requested but not actually used memory?

The latter. (MemFree is physical memory, not virtual memory, by the

> If the latter, where can one see the amount of unrequested memory?

It's CommitLimit - Committed_AS. At one point there was a CommitAvail
but it looks like it was removed in 2.6.10 because it's redundant:

BTW, with overcommit_memory=2,
CommitLimit = (MemTotal * (overcommit_ratio / 100)) + SwapFree

With the default of overcommit_ratio = 50, this simplifies to:
CommitLimit = (MemTotal / 2) + SwapFree

Unless you're setting overcommit_ratio to 100, this means that with
640MB of RAM and no swap, user programs are allowed to request 320MB of
memory at most.

I hope this helps...

-Barry K. Nathan <barryn at>

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