Re: RSS Limit implementation issue

[Bill Davidsen]

Peter Chubb wrote:

> > > > > > "Bill" == Bill Davidsen <davidsen@xxxxxxx> 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@xxxxxxx>
 CTO TMR Associates, Inc
 Doing interesting things with small computers since 1979

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