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To: "David Magda" <dmagda@ee.ryerson.ca>
Cc: freebsd-stable@freebsd.org
Subject: Re: protecting some processes from out-of-swap killer
References: <alpine.BSF.2.00.1504251316020.43520@woozle.rinet.ru>
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Date: Thu, 30 Apr 2015 10:59:32 +0200
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From: "Ronald Klop" <ronald-lists@klop.ws>
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On Wed, 29 Apr 2015 19:09:05 +0200, David Magda <dmagda@ee.ryerson.ca>  
wrote:

> 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:  
https://wiki.freebsd.org/SystemTuning and in man tuning(7).

Regards,
Ronald.