From: "J. Bruce Fields" <bfields@fieldses.org>
To: Alexandre Depoutovitch <adepoutovitch@vmware.com>
Cc: linux-nfs@vger.kernel.org
Subject: Re: About Direct I/O
Date: Fri, 16 Mar 2012 16:35:21 -0400 [thread overview]
Message-ID: <20120316203521.GA22929@fieldses.org> (raw)
In-Reply-To: <6866525b.00001bd8.0000023d@aldep-VC.vmware.com>
On Fri, Mar 16, 2012 at 11:14:04AM -0700, Alexandre Depoutovitch wrote:
> Hello,
> I am trying to do random sector aligned writes to an NFS mounted disk. The
> performance is order of magnitude worse than 4K (file system block size)
> aligned I/O.
> The reason is that NFS demon (Linux kernel 2.6.32) on the server side
> always does buffered I/O, which behaves poorly for block unaligned
> requests.
> Is there a way to tell NFS daemon to use direct I/O?
No.
> If not, is it an implementation limitation or there is a fundamental
> problem with using direct I/O in NFS server?
I'm shamefully ignorant of Direct IO....
If we supported Direct IO, are there heuristics that would let the
server figure out on its own when it helped and when it didn't? Or
would the administrator be stuck trying to figure that out?
Is Direct IO possible from kernel buffers these days? Are there
alignment restrictions?
--b.
next prev parent reply other threads:[~2012-03-16 20:35 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-15 20:23 About pNFS installation process Bruno Silva
2012-03-16 0:16 ` Jim Rees
2012-03-16 18:14 ` About Direct I/O Alexandre Depoutovitch
2012-03-16 20:35 ` J. Bruce Fields [this message]
2012-03-16 20:58 ` Myklebust, Trond
2012-03-18 10:51 ` About pNFS installation process Lev Solomonov
2012-03-23 17:21 ` Bruno Silva
2012-03-23 18:02 ` Jim Rees
2012-04-04 0:20 ` Lev Solomonov
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=20120316203521.GA22929@fieldses.org \
--to=bfields@fieldses.org \
--cc=adepoutovitch@vmware.com \
--cc=linux-nfs@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