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SubjectRe: RSS Limit implementation issue
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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