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

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Message-Id: <20110128172438.6c49d4ea.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 28 Jan 2011 17:24:38 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	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>,
	"hannes@...xchg.org" <hannes@...xchg.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

On Fri, 28 Jan 2011 17:04:16 +0900
Minchan Kim <minchan.kim@...il.com> 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?
> 

You're right. But
 - This patch oder doesn't affect bi-sect of the bug. because 
   2 bugs seems to be the same.
 - This patch implements a leaf function for the real fix.

Then, I think patch order is not problem here.

Thank you for pointing out.

Thanks,
-Kame




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