Message-ID: <442CA294.7010902@tmr.com>
Date: Thu, 30 Mar 2006 22:31:32 -0500
From: Bill Davidsen <davidsen@tmr.com>
Organization: TMR Associates Inc, Schenectady NY
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To: Peter Chubb <peterc@gelato.unsw.edu.au>
CC: Ram Gupta <ram.gupta5@gmail.com>,
       linux mailing-list <linux-kernel@vger.kernel.org>
Subject: Re: RSS Limit implementation issue
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Peter Chubb wrote:

>>>>>>"Bill" == Bill Davidsen <davidsen@tmr.com> writes:
>>>>>>            
>>>>>>
>
>Bill> Ram Gupta wrote:
>
>Bill> If you want to make rss a hard limit the result should be
>Bill> swapping, not failure to run. I'm not sure the limit in that
>Bill> form is a good idea, and before someone reminds me, I do
>Bill> remember liking it better a few years ago.
>
>Bill> If you can come up with a better way to adjust rss to get better
>Bill> overall greater throughput while being fair to all processes, go
>Bill> to it. But in general these things are a tradeoff, like
>Bill> swappiness, you tune until the volume of complaints reaches a
>Bill> minimum.
>
>What I did in one experiment was to:
>     1.  delay swapin requests if the process was over its rsslimit,
>         until it fell below, and
>     2.  Poke the swapper to try to swap out the current process's
>         pages in that case.
>
>The problem with the approach is that it behaved poorly under memory
>pressure.  If a process's optimum working set was larger than its RSS
>limit, then either it was delayed to the point of glaciality, or it
>could saturate the swap device (and so disturb other processes's
>operation). 
>
>  
>
I'm paying close attention, but that's kind of the problem people have, 
memory pressure gets high and the processes don't run. I thought of 
"swap out two to swap in one" as a way to dribble the rss down, but I 
doubt it's a magic solution. Swap kills, so does not swap and no memory. 
Obvious solution is to make the rss limit hard and keep it small, I 
don't think that's the answer.

-- 
bill davidsen <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979

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