linux-kernel - Re: additional oom-killer tuneable worth submitting?

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Message-ID: <4578A1F1.7050907@nortel.com>
Date:	Thu, 07 Dec 2006 17:21:21 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	Alan <alan@...rguk.ukuu.org.uk>
CC:	linux-kernel@...r.kernel.org
Subject: Re: additional oom-killer tuneable worth submitting?

Alan wrote:

>>The "oom-thresh" value maps to the max expected memory consumption for 
>>that process.  As long as a process uses less memory than the specified 
>>threshold, then it is immune to the oom-killer.

> You've just introduced a deadlock. What happens if nobody is over that
> predicted memory and the kernel uses more resource ?

Based on the discussion with Jesper, we fall back to regular behaviour. 
  (Or possibly hang or reboot, if we added another switch).

>>On an embedded platform this allows the designer to engineer the system 
>>and protect critical apps based on their expected memory consumption. 
>>If one of those apps goes crazy and starts chewing additional memory 
>>then it becomes vulnerable to the oom killer while the other apps remain 
>>protected.

> That is why we have no-overcommit support. Now there is an argument for
> a meaningful rlimit-as to go with it, and together I think they do what
> you really need.

No overcommit only protects the system as a whole, not any particular 
processes.  The purpose of this is to protect specific daemons from 
being killed when the system as a whole is short on memory.  Same 
rationale as for oomadj, but different knob to twiddle.

Chris
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