From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <jaxboe@fusionio.com>
Cc: Vivek Goyal <vgoyal@redhat.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
czoccolo@gmail.com
Subject: Re: trying to understand READ_META, READ_SYNC, WRITE_SYNC & co
Date: Sat, 26 Jun 2010 13:56:32 +0200 [thread overview]
Message-ID: <20100626115632.GA31209@lst.de> (raw)
In-Reply-To: <20100626112054.GA30661@kernel.dk>
On Sat, Jun 26, 2010 at 01:20:55PM +0200, Jens Axboe wrote:
> The whole idling/anticipation is all about knowing when to
> stall the queue very briefly for sync io, allowing that single
> sync stream to make good progress for a while before switching
> to something else. This switching back and forth potentially
> destroyes throughput for the O_DIRECT writer, especially for
> disks with write through caching.
>
> Christoph, you seem not to agree on the concept of idling.
I'm still trying to understand the use case. Basically CFQ gets
worse results for any workload I'm looking at, be that from the
filesystem developer point of view, or virtualization point of
view. And it tends to get worse the more intelligence is added
to CFQ.
If we could actually narrow down what it's supposed to help
with into useful benchmarks that can be trivially reproduced a
lot of things would be easier.
next prev parent reply other threads:[~2010-06-26 11:56 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-21 9:48 trying to understand READ_META, READ_SYNC, WRITE_SYNC & co Christoph Hellwig
2010-06-21 10:04 ` Jens Axboe
2010-06-21 11:04 ` Christoph Hellwig
2010-06-21 18:56 ` Jens Axboe
2010-06-21 19:14 ` Christoph Hellwig
2010-06-21 19:16 ` Jens Axboe
2010-06-21 19:20 ` Christoph Hellwig
2010-06-21 21:36 ` Vivek Goyal
2010-06-23 10:01 ` Christoph Hellwig
2010-06-24 1:44 ` Vivek Goyal
2010-06-25 11:03 ` Christoph Hellwig
2010-06-26 3:35 ` Vivek Goyal
2010-06-26 10:05 ` Christoph Hellwig
2010-06-26 11:20 ` Jens Axboe
2010-06-26 11:56 ` Christoph Hellwig [this message]
2010-06-27 15:44 ` Jeff Moyer
2010-06-29 9:06 ` Corrado Zoccolo
2010-06-29 12:30 ` Vivek Goyal
2010-06-30 15:30 ` Corrado Zoccolo
2010-06-26 9:25 ` Nick Piggin
2010-06-26 9:27 ` Christoph Hellwig
2010-06-26 10:10 ` Nick Piggin
2010-06-26 10:16 ` Christoph Hellwig
2010-06-21 18:52 ` Jeff Moyer
2010-06-21 18:58 ` Jens Axboe
2010-06-21 19:08 ` Jeff Moyer
2010-06-23 9:26 ` Christoph Hellwig
2010-06-21 20:25 ` Vivek Goyal
2010-06-23 10:02 ` 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=20100626115632.GA31209@lst.de \
--to=hch@lst.de \
--cc=czoccolo@gmail.com \
--cc=jaxboe@fusionio.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=vgoyal@redhat.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;
as well as URLs for NNTP newsgroup(s).