Re: [RFC][PATCH 5/5] Memory controller soft limit reclaim on contention (v8)

[Balbir Singh <balbir@linux.vnet.ibm.com>]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-07-10 23:15:20]:

> Balbir Singh wrote?$B!'
> > * Balbir Singh <balbir@linux.vnet.ibm.com> [2009-07-10 13:19:06]:
> >>
> >> Yes, worth experimenting with, I'll redo with the special code
> >> removed.
> >
> >
> > OK, so I experimented with it, I found the following behaviour
> >
> > 1. We try to reclaim, priority is high, scanned pages are low and
> >    hence memory cgroup zone reclaim returns 0 (no pages could be
> >    reclaimed).
> > 2. Now regular reclaim from balance_pgdat() is called, it is able
> >    to shrink from global LRU and hence some other mem cgroup, thus
> >    breaking soft limit semantics.
> >
> IMO, "breaking soft limit" cannot be an excuse for delaying kswapd too much.
>

Hmmm... I agree in principle, but if soft limits are turned on, we are
overriding where we should be reclaiming from. The delay IMHO is not
very high and I've run tests without setting any soft limits but with
soft limits feature enabled. I don't see anything going bad or any
overhead.

I've just posted v9 without the changes. I'll do some runs with your
suggestion and see what the complete impact is.
 

-- 
	Balbir

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