From: Werner Almesberger <wa@almesberger.net>
To: Jens Axboe <axboe@suse.de>
Cc: linux-fsdevel@vger.kernel.org
Subject: Re: barriers vs. reads
Date: Tue, 22 Jun 2004 04:50:04 -0300 [thread overview]
Message-ID: <20040622045004.C1325@almesberger.net> (raw)
In-Reply-To: <20040622073919.GV12881@suse.de>; from axboe@suse.de on Tue, Jun 22, 2004 at 09:39:20AM +0200
Jens Axboe wrote:
> I don't think a read-barrier currently has a meaning. A write barrier
> will force ordering for later reads too, of course.
That's one of the problem spots with priorities: if there are a
lot of writes in the queue, high-priority reads will be delayed
for a long time.
But do we have cases where reads must not cross write barriers ?
> It can't, the insert position doesn't tell you whether it's a barrier or
> not. You have to check ->flags for that.
Yet deadline, AS, and CFQ don't do any such check :-)
- Werner
--
_________________________________________________________________________
/ Werner Almesberger, Buenos Aires, Argentina wa@almesberger.net /
/_http://www.almesberger.net/____________________________________________/
next prev parent reply other threads:[~2004-06-22 7:50 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-06-22 3:53 barriers vs. reads Werner Almesberger
2004-06-22 7:39 ` Jens Axboe
2004-06-22 7:50 ` Werner Almesberger [this message]
2004-06-22 7:55 ` Jens Axboe
2004-06-22 8:34 ` Werner Almesberger
2004-06-22 10:08 ` Jens Axboe
2004-06-22 11:28 ` Jamie Lokier
2004-06-22 11:32 ` Jens Axboe
2004-06-22 17:12 ` Bryan Henderson
2004-06-22 20:53 ` Jens Axboe
2004-06-23 16:41 ` Bryan Henderson
2004-06-23 16:52 ` Jens Axboe
2004-06-23 16:53 ` Jamie Lokier
2004-06-23 21:08 ` Bryan Henderson
2004-06-23 23:23 ` Werner Almesberger
2004-06-24 13:43 ` Jamie Lokier
2004-06-24 14:32 ` Christoph Hellwig
2004-06-24 17:05 ` Werner Almesberger
2004-06-22 18:53 ` Werner Almesberger
2004-06-22 19:57 ` Jamie Lokier
2004-06-22 23:13 ` Werner Almesberger
2004-06-22 20:57 ` Jens Axboe
2004-06-22 23:10 ` Werner Almesberger
2004-06-23 0:14 ` Jamie Lokier
2004-06-23 6:27 ` Jens Axboe
2004-06-22 18:45 ` Werner Almesberger
2004-06-22 19:07 ` Guy
-- strict thread matches above, loose matches on Subject: below --
2004-06-24 0:48 Werner Almesberger
2004-06-24 3:39 ` Werner Almesberger
2004-06-24 8:00 ` Herbert Poetzl
2004-06-24 12:16 ` Werner Almesberger
2004-06-24 13:36 ` Jamie Lokier
2004-06-24 17:02 ` Werner Almesberger
2004-06-24 16:39 ` Steve Lord
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=20040622045004.C1325@almesberger.net \
--to=wa@almesberger.net \
--cc=axboe@suse.de \
--cc=linux-fsdevel@vger.kernel.org \
/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).