linux-kernel - Re: [BUGFIX][PATCH 1/4] memcg: fix limit estimation at reclaim for hugepage

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Message-ID: <AANLkTinikUM09bXbLZ5zU1gdgfdPZSQmbycbbeSyGk59@mail.gmail.com>
Date:	Fri, 28 Jan 2011 17:25:58 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>
Subject: Re: [BUGFIX][PATCH 1/4] memcg: fix limit estimation at reclaim for hugepage

Hi Hannes,

On Fri, Jan 28, 2011 at 5:17 PM, Johannes Weiner <hannes@...xchg.org> wrote:
> On Fri, Jan 28, 2011 at 05:04:16PM +0900, Minchan Kim wrote:
>> Hi Kame,
>>
>> On Fri, Jan 28, 2011 at 1:58 PM, KAMEZAWA Hiroyuki
>> <kamezawa.hiroyu@...fujitsu.com> wrote:
>> > How about this ?
>> > ==
>> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>> >
>> > Current memory cgroup's code tends to assume page_size == PAGE_SIZE
>> > and arrangement for THP is not enough yet.
>> >
>> > This is one of fixes for supporing THP. This adds
>> > mem_cgroup_check_margin() and checks whether there are required amount of
>> > free resource after memory reclaim. By this, THP page allocation
>> > can know whether it really succeeded or not and avoid infinite-loop
>> > and hangup.
>> >
>> > Total fixes for do_charge()/reclaim memory will follow this patch.
>>
>> If this patch is only related to THP, I think patch order isn't good.
>> Before applying [2/4], huge page allocation will retry without
>> reclaiming and loop forever by below part.
>>
>> @@ -1854,9 +1858,6 @@ static int __mem_cgroup_do_charge(struct
>>       } else
>>               mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
>>
>> -     if (csize > PAGE_SIZE) /* change csize and retry */
>> -             return CHARGE_RETRY;
>> -
>>       if (!(gfp_mask & __GFP_WAIT))
>>               return CHARGE_WOULDBLOCK;
>>
>> Am I missing something?
>
> No, you are correct.  But I am not sure the order really matters in
> theory: you have two endless loops that need independent fixing.

That's why I ask a question.
Two endless loop?

One is what I mentioned. The other is what?
Maybe this patch solve the other.
But I can't guess it by only this description. Stupid..

Please open my eyes.

-- 
Kind regards,
Minchan Kim
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