From: Ted Ts'o <tytso@mit.edu>
To: Jan Kara <jack@suse.cz>
Cc: Ext4 Developers List <linux-ext4@vger.kernel.org>
Subject: Re: [PATCH] ext4: fake direct I/O mode for data=journal
Date: Mon, 15 Aug 2011 14:03:11 -0400 [thread overview]
Message-ID: <20110815180311.GC5948@thunk.org> (raw)
In-Reply-To: <20110815115939.GA6971@quack.suse.cz>
On Mon, Aug 15, 2011 at 01:59:39PM +0200, Jan Kara wrote:
> Why have you chosen to set O_DSYNC?
O_DSYNC was the closest thing to O_DIRECT, in that writes get forced
to disk after the write finished. I did this fix a test failure
caused by missing direct I/O writes with a buffered read. OTOH, there
is a performance cost in doing this since it will force a journal
commit after every write. That's probably not acceptable. Hmph.
> Also what about reads? Mixing of buffered writes and direct IO reads will
> not work because filemap_write_and_write() does not write data block to the
> final location on disk but only to a journal.
Given that, we're probably better off forcing reads drop O_DIRECT as
well and drop O_DSYNC.
I'll change the patch and then give it a test.
- Ted
next prev parent reply other threads:[~2011-08-15 18:03 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-15 2:19 [PATCH] ext4: fake direct I/O mode for data=journal Theodore Ts'o
2011-08-15 11:59 ` Jan Kara
2011-08-15 18:03 ` Ted Ts'o [this message]
2011-08-16 19:32 ` [PATCH -v2] " Theodore Ts'o
2011-08-17 11:42 ` Jan Kara
2011-08-17 16:50 ` Ted Ts'o
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=20110815180311.GC5948@thunk.org \
--to=tytso@mit.edu \
--cc=jack@suse.cz \
--cc=linux-ext4@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 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.