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From: Fengguang Wu <fengguang.wu@intel.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.cz>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujtisu.com>,
	Minchan Kim <minchan@kernel.org>, Rik van Riel <riel@redhat.com>,
	Ying Han <yinghan@google.com>, Greg Thelen <gthelen@google.com>,
	Hugh Dickins <hughd@google.com>,
	Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH -mm] memcg: prevent from OOM with too many dirty pages
Date: Wed, 20 Jun 2012 17:55:46 +0800	[thread overview]
Message-ID: <20120620095546.GB8765@localhost> (raw)
In-Reply-To: <20120620092011.GB4011@suse.de>

> > Finally, I wonder if there should be some timeout of that wait.  I
> > don't know why, but I wouldn't be surprised if we hit some glitch which
> > causes us to add one!
> > 
> 
> If we hit such a situation it means that flush is no longer working which
> is interesting in itself. I guess one possibility where it can occur is
> if we hit global dirty limits (or memcg dirty limits when they exist)
> and the page is backed by NFS that is disconnected. That would stall here
> potentially forever but it's already the case that a system that hits its
> dirty limits with a disconnected NFS is in trouble and a timeout here will
> not do much to help.

Agreed. I've run into such cases and cannot login even locally because
the shell will be blocked trying to write even 1 byte at startup time. 
Any opened shells are also stalled on writing to .bash_history etc.

Thanks,
Fengguang

WARNING: multiple messages have this Message-ID (diff)
From: Fengguang Wu <fengguang.wu@intel.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.cz>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujtisu.com>,
	Minchan Kim <minchan@kernel.org>, Rik van Riel <riel@redhat.com>,
	Ying Han <yinghan@google.com>, Greg Thelen <gthelen@google.com>,
	Hugh Dickins <hughd@google.com>,
	Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH -mm] memcg: prevent from OOM with too many dirty pages
Date: Wed, 20 Jun 2012 17:55:46 +0800	[thread overview]
Message-ID: <20120620095546.GB8765@localhost> (raw)
In-Reply-To: <20120620092011.GB4011@suse.de>

> > Finally, I wonder if there should be some timeout of that wait.  I
> > don't know why, but I wouldn't be surprised if we hit some glitch which
> > causes us to add one!
> > 
> 
> If we hit such a situation it means that flush is no longer working which
> is interesting in itself. I guess one possibility where it can occur is
> if we hit global dirty limits (or memcg dirty limits when they exist)
> and the page is backed by NFS that is disconnected. That would stall here
> potentially forever but it's already the case that a system that hits its
> dirty limits with a disconnected NFS is in trouble and a timeout here will
> not do much to help.

Agreed. I've run into such cases and cannot login even locally because
the shell will be blocked trying to write even 1 byte at startup time. 
Any opened shells are also stalled on writing to .bash_history etc.

Thanks,
Fengguang

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  reply	other threads:[~2012-06-20  9:55 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-06-19 14:50 [PATCH -mm] memcg: prevent from OOM with too many dirty pages Michal Hocko
2012-06-19 14:50 ` Michal Hocko
2012-06-19 22:00 ` Andrew Morton
2012-06-19 22:00   ` Andrew Morton
2012-06-20  8:27   ` Michal Hocko
2012-06-20  8:27     ` Michal Hocko
2012-06-20  9:20   ` Mel Gorman
2012-06-20  9:20     ` Mel Gorman
2012-06-20  9:55     ` Fengguang Wu [this message]
2012-06-20  9:55       ` Fengguang Wu
2012-06-20  9:59     ` Michal Hocko
2012-06-20  9:59       ` Michal Hocko
2012-06-20 10:11   ` [PATCH v2 " Michal Hocko
2012-06-20 10:11     ` Michal Hocko
2012-07-12  1:57     ` Hugh Dickins
2012-07-12  1:57       ` Hugh Dickins
2012-07-12  2:21       ` Andrew Morton
2012-07-12  2:21         ` Andrew Morton
2012-07-12  3:13         ` Hugh Dickins
2012-07-12  3:13           ` Hugh Dickins
2012-07-12  7:05       ` Michal Hocko
2012-07-12  7:05         ` Michal Hocko
2012-07-12 21:13         ` Andrew Morton
2012-07-12 21:13           ` Andrew Morton
2012-07-12 22:42           ` Hugh Dickins
2012-07-12 22:42             ` Hugh Dickins
2012-07-13  8:21             ` Michal Hocko
2012-07-13  8:21               ` Michal Hocko
2012-07-16  8:30               ` Hugh Dickins
2012-07-16  8:30                 ` Hugh Dickins
2012-07-16  8:35                 ` [PATCH mmotm] memcg: further prevent " Hugh Dickins
2012-07-16  8:35                   ` Hugh Dickins
2012-07-16  9:26                   ` Michal Hocko
2012-07-16  9:26                     ` Michal Hocko
2012-07-17  4:52                     ` Hugh Dickins
2012-07-17  4:52                       ` Hugh Dickins
2012-07-17  6:33                       ` Michal Hocko
2012-07-17  6:33                         ` Michal Hocko
2012-07-16 21:08                   ` Andrew Morton
2012-07-16 21:08                     ` Andrew Morton
2012-07-16  8:10         ` [PATCH v2 -mm] memcg: prevent from " Hugh Dickins
2012-07-16  8:10           ` Hugh Dickins
2012-07-16  8:48           ` Michal Hocko
2012-07-16  8:48             ` Michal Hocko

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