linux-kernel - Re: Deadlock possibly caused by too_many

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Message-ID: <20101019023537.GB8310@localhost>
Date:	Tue, 19 Oct 2010 10:35:37 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Minchan Kim <minchan.kim@...il.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.

> @@ -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.

Thanks,
Fengguang
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