From: Andrew Morton <akpm@linux-foundation.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Dan Ehrenberg <dehrenberg@google.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dio: Fast-path for page-aligned IOs
Date: Wed, 27 Jul 2011 14:14:15 -0700 [thread overview]
Message-ID: <20110727141415.a67cafb8.akpm@linux-foundation.org> (raw)
In-Reply-To: <20110727210828.GB12714@infradead.org>
On Wed, 27 Jul 2011 17:08:28 -0400
Christoph Hellwig <hch@infradead.org> wrote:
> On Mon, Jun 20, 2011 at 04:17:35PM -0700, Dan Ehrenberg wrote:
> > The fast path does not apply for operations of the wrong size
> > or alignmnent, or for operations on raw drives with 512-byte sectors.
> > It might be possible to make this special case a little more general
> > while maintaining its performance benefits, but I do not believe that
> > the full performance benefits can be achieved without resorting to
> > special handling of simple cases, as is done in this patch.
>
> Did you check how this compares to Andis small optimizations?
>
> Also operations on raw disks are something people with fast devices
> care about a lot. We often hear about benchmark regressions due to
> stupid little things in the direct I/O code.
>
> If we want to special case something that would be a very easy target,
> with a 1:1 mapping of logical to physical blocks and thus no need
> to call the allocator first, and no need for any kind of locking
> or alignment handling.
Ken did this back in 2006
(http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=e61c90188b9956edae1105eef361d8981a352fcd)
but we reverted that shortly afterwards for some reason.
next prev parent reply other threads:[~2011-07-27 21:14 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-20 23:17 [PATCH] dio: Fast-path for page-aligned IOs Dan Ehrenberg
2011-06-21 20:41 ` Andi Kleen
2011-06-21 21:21 ` Daniel Ehrenberg
2011-06-21 21:21 ` Daniel Ehrenberg
2011-06-21 21:44 ` Andi Kleen
2011-06-21 21:44 ` Andi Kleen
2011-06-29 21:03 ` Theodore Ts'o
2011-07-27 21:08 ` Christoph Hellwig
2011-07-27 21:14 ` Andrew Morton [this message]
2011-07-27 22:15 ` Jeff Moyer
2011-07-28 22:09 ` Daniel Ehrenberg
2011-07-28 22:09 ` Daniel Ehrenberg
2011-07-28 22:10 ` Daniel Ehrenberg
2011-07-28 22:10 ` Daniel Ehrenberg
-- strict thread matches above, loose matches on Subject: below --
2011-06-20 22:44 Dan Ehrenberg
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=20110727141415.a67cafb8.akpm@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=dehrenberg@google.com \
--cc=hch@infradead.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=viro@zeniv.linux.org.uk \
/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.