linux-kernel - Re: [RFC][PATCH 1/5] memcg: change for softlimit.

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Message-ID: <20090828151528.GT4889@balbir.in.ibm.com>
Date:	Fri, 28 Aug 2009 20:45:28 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>
Subject: Re: [RFC][PATCH 1/5] memcg: change for softlimit.

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-08-29 00:12:26]:

> Balbir Singh wrote:
> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-08-29
> > 00:06:23]:
> >
> >> Balbir Singh wrote:
> >> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-08-28
> >> > 23:40:56]:
> >> >
> >> >> KAMEZAWA Hiroyuki wrote:
> >> >> > Balbir Singh wrote:
> >> >> >> But Bob and Mike might need to set soft limits between themselves.
> >> if
> >> >> >> soft limit of gold is 1G and bob needs to be close to 750M and
> >> mike
> >> >> >> 250M, how do we do it without supporting what we have today?
> >> >> >>
> >> >> > Don't use hierarchy or don't use softlimit.
> >> >> > (I never think fine-grain  soft limit can be useful.)
> >> >> >
> >> >> > Anyway, I have to modify unnecessary hacks for res_counter of
> >> >> softlimit.
> >> >> > plz allow modification. that's bad.
> >> >> > I postpone RB-tree breakage problem, plz explain it or fix it by
> >> >> yourself.
> >> >> >
> >> >> I changed my mind....per-zone RB-tree is also broken ;)
> >> >>
> >> >> Why I don't like broken system is a function which a user can't
> >> >> know/calculate how-it-works is of no use in mission critical systems.
> >> >>
> >> >> I'd like to think how-to-fix it with better algorithm. Maybe RB-tree
> >> >> is not a choice.
> >> >>
> >> >
> >> > Soft limits are not meant for mission critical work :-) Soft limits is
> >> > best effort and not a guaranteed resource allocation mechanism. I've
> >> > mentioned in previous emails how we recover if we find the data is
> >> > stale
> >> >
> >> yes. but can you explain how selection will be done to users ?
> >> I can't.
> >>
> >
> > From a user point, we get what we set, but the timelines can be a
> > little longer.
> >
> I'll drop this patch, anyway. But will modify res_counter.
> We have to reduce ops under lock after we see spinlock can explode
> system time.
>

Thanks! I'll review the other patches as well and test them sometime
over the weekend. 

-- 
	Balbir
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