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

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Message-ID: <25afd2b84c65e7c2c8f2edde31c914f7.squirrel@webmail-b.css.fujitsu.com>
Date:	Sat, 29 Aug 2009 00:12:26 +0900 (JST)
From:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	"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.

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,
-Kame

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