linux-kernel - Re: Deadlock possibly caused by too_many

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Date:	Tue, 19 Oct 2010 11:52:47 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Neil Brown <neilb@...e.de>, Rik van Riel <riel@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"Li, Shaohua" <shaohua.li@...el.com>
Subject: Re: Deadlock possibly caused by too_many_isolated.

Hi Wu,

On Tue, Oct 19, 2010 at 11:35 AM, Wu Fengguang <fengguang.wu@...el.com> wrote:
>> @@ -2054,10 +2069,11 @@ rebalance:
>>                 goto got_pg;
>>
>>         /*
>> -        * If we failed to make any progress reclaiming, then we are
>> -        * running out of options and have to consider going OOM
>> +        * If we failed to make any progress reclaiming and there aren't
>> +        * many parallel reclaiming, then we are unning out of options and
>> +        * have to consider going OOM
>>          */
>> -       if (!did_some_progress) {
>> +       if (!did_some_progress && !too_many_isolated_zone(preferred_zone)) {
>>                 if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
>>                         if (oom_killer_disabled)
>>                                 goto nopage;
>
> This is simply wrong.
>
> It disabled this block for 99% system because there won't be enough
> tasks to make (!too_many_isolated_zone == true). As a result the LRU
> will be scanned like mad and no task get OOMed when it should be.

If !too_many_isolated_zone is false, it means there are already many
direct reclaiming tasks.
So they could exit reclaim path and !too_many_isolated_zone will be true.
What am I missing now?


> Thanks,
> Fengguang
>



-- 
Kind regards,
Minchan Kim
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