From: Dan Merillat <dan.merillat@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: martin f krafft <madduck@madduck.net>,
linux kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: Abysmal I/O scheduling with dm-crypt
Date: Wed, 7 Sep 2011 22:51:43 -0400 [thread overview]
Message-ID: <CAPL5yKcRbYEsiZwyiT5aMfcmNUi_gam5Pj_ks_Apj-fE=Lc4KA@mail.gmail.com> (raw)
In-Reply-To: <20110905153758.GJ5466@quack.suse.cz>
> On Tue 30-08-11 09:14:07, martin f krafft wrote:
>> People not running dm-crypt seem unable to reproduce this problem,
>> making me think that it must be due to dm-crypt, and I wouldn't find
>> it hard to imagine, because dm-crypt basically shields the
>> I/O-scheduler of the kernel, doesn't it? Worse, it probably doesn't
>> make any effort of scheduling I/O itself. Note: I know very little
>> about the internals, so please correct me if I am wrong.
No, it's not specific to dm-crypt, these kinds of annoying IO hangs happen
on bare drives, MD arrays or DM-* setups.
There's a number of causes - including firefox history updates and the
abuse of create/sync/rename due to metadata hitting disk before data.
There's not going to be any movement on that front, I'm afraid, see
"Don't fear the fsync" (reproduced at
http://www.linuxfoundation.org/news-media/blogs/browse/2009/03/don%E2%80%99t-fear-fsync
, the original site couldn't be reached while I'm writing this).
You can either throw more hardware at it, or use libeatmydata to
disable fsync across the board. Maybe, eventually, a filesystem will
be written that can manage an atomic replace without fsync(). Don't
hold your breath.
next prev parent reply other threads:[~2011-09-08 2:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-30 7:14 Abysmal I/O scheduling with dm-crypt martin f krafft
2011-09-05 15:37 ` Jan Kara
2011-09-08 2:51 ` Dan Merillat [this message]
2011-09-19 18:39 ` Valdis.Kletnieks
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAPL5yKcRbYEsiZwyiT5aMfcmNUi_gam5Pj_ks_Apj-fE=Lc4KA@mail.gmail.com' \
--to=dan.merillat@gmail.com \
--cc=jack@suse.cz \
--cc=linux-kernel@vger.kernel.org \
--cc=madduck@madduck.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.