linux-ext4 - Re: Excessive stall times on ext4 in 3.9-rc2

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130410131245.GC4862@thunk.org>
Date:	Wed, 10 Apr 2013 09:12:45 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Mel Gorman <mgorman@...e.de>
Cc:	linux-ext4@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>, Jiri Slaby <jslaby@...e.cz>
Subject: Re: Excessive stall times on ext4 in 3.9-rc2

On Wed, Apr 10, 2013 at 11:56:08AM +0100, Mel Gorman wrote:
> During major activity there is likely to be "good" behaviour
> with stalls roughly every 30 seconds roughly corresponding to
> dirty_expire_centiseconds. As you'd expect, the flusher thread is stuck
> when this happens.
> 
>   237 ?        00:00:00 flush-8:0
> [<ffffffff811a35b9>] sleep_on_buffer+0x9/0x10
> [<ffffffff811a35ee>] __lock_buffer+0x2e/0x30
> [<ffffffff8123a21f>] do_get_write_access+0x43f/0x4b0

If we're stalling on lock_buffer(), that implies that buffer was being
written, and for some reason it was taking a very long time to
complete.

It might be worthwhile to put a timestamp in struct dm_crypt_io, and
record the time when a particular I/O encryption/decryption is getting
queued to the kcryptd workqueues, and when they finally squirt out.

Something else that might be worth trying is to add WQ_HIGHPRI to the
workqueue flags and see if that makes a difference.

	  	    	   	- Ted
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html