From: Dave Chinner <david@fromorbit.com>
To: Michael Monnerie <michael.monnerie@is.it-management.at>
Cc: Christoph Hellwig <hch@infradead.org>,
Wu Fengguang <fengguang.wu@intel.com>,
xfs@oss.sgi.com
Subject: Re: [PATCH] xfs: improve sync behaviour in face of aggressive dirtying
Date: Wed, 22 Jun 2011 10:19:37 +1000 [thread overview]
Message-ID: <20110622001937.GR32466@dastard> (raw)
In-Reply-To: <201106210921.48657@zmi.at>
On Tue, Jun 21, 2011 at 09:21:46AM +0200, Michael Monnerie wrote:
> On Dienstag, 21. Juni 2011 Dave Chinner wrote:
> > > The minor one is that we always flush all work items and not just
> > > those on the filesystem to be flushed. This might become an issue
> > > for lager systems, or when we apply a similar scheme to fsync,
> > > which has the same underlying issue.
> >
> > For sync, I don't think it matters if we flush a few extra IO
> > completions on a busy system.
>
> Couldn't that be bad on a system with mixed fast/slow storage (say 15k
> SAS and 7.2k SATA), where on the busy fast SAS lots of syncs occur and
> lead to extra I/O on the SATA disks? Especially if there are 16 SAS
> disks in an array with RAID-0 against 4 SATA disks in RAID-6, to say the
> worst. If the SATAs are already heavy used (say >=50%), those extra
> writes could bring them to their knees.
We are not talking about issuing extra writes to disk, so you don't
have to worry about this. What we are talking about is how to
efficiently flush the XFS IO completion queues for writes that the
hardware has already completed. That's almost always just CPU
overhead and doesn't involve more IO.... ;)
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs
next prev parent reply other threads:[~2011-06-22 0:19 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-17 13:14 [PATCH] xfs: improve sync behaviour in face of aggressive dirtying Christoph Hellwig
2011-06-20 8:18 ` Christoph Hellwig
2011-06-21 0:33 ` Dave Chinner
2011-06-21 7:21 ` Michael Monnerie
2011-06-22 0:19 ` Dave Chinner [this message]
2011-06-21 9:29 ` Christoph Hellwig
2011-06-22 1:09 ` Dave Chinner
2011-06-22 6:51 ` Christoph Hellwig
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=20110622001937.GR32466@dastard \
--to=david@fromorbit.com \
--cc=fengguang.wu@intel.com \
--cc=hch@infradead.org \
--cc=michael.monnerie@is.it-management.at \
--cc=xfs@oss.sgi.com \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox