protecting some processes from out-of-swap killer

Ronald Klop ronald-lists at
Thu Apr 30 08:59:49 UTC 2015

On Wed, 29 Apr 2015 19:09:05 +0200, David Magda <dmagda at>  

> On Tue, April 28, 2015 05:51, Ronald Klop wrote:
>> The OS trying to kill a process is probably not what you want. So when  
>> you
>> protect(1) postgres the OS will kill another process, which I hope is  
>> not
>> running without reason.
>> My advice would be to
>> - or increase your swap space
>> - or tune postgresql to use less memory
>> - or limit tmpfs (tmpfs uses swap if RAM is short)
>> - or tune zfs to use less memory
> Personally I didn't even know FreeBSD had an OOM killer. I regularly run
> into Linux's though, but that's because by default Linux allows
> over-committing of memory.
> I was under the impression that FreeBSD did not over-subscribe memory,  
> and
> so would not allow a process to do a malloc() unless there was enough
> RAM+swap to satisfy it.
> Is this a mistaken assumption? (I probably have to buy the McKusick,
> Neville-Neil, Watson book.)

See sysctl vm.overcommit, which is also documented here: and in man tuning(7).


More information about the freebsd-stable mailing list