From: Jeff Moyer <jmoyer@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>,
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 18:15:53 -0400 [thread overview]
Message-ID: <x49vcuns73a.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <20110727141415.a67cafb8.akpm@linux-foundation.org> (Andrew Morton's message of "Wed, 27 Jul 2011 14:14:15 -0700")
Andrew Morton <akpm@linux-foundation.org> writes:
> 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.
For this reason:
commit b2e895dbd80c420bfc0937c3729b4afe073b3848
Author: Andrew Morton <akpm@osdl.org>
Date: Sat Feb 3 01:14:01 2007 -0800
[PATCH] revert blockdev direct io back to 2.6.19 version
Andrew Vasquez is reporting as-iosched oopses and a 65% throughput
slowdown due to the recent special-casing of direct-io against
blockdevs. We don't know why either of these things are occurring.
The patch minimally reverts us back to the 2.6.19 code for a 2.6.20
release.
next prev parent reply other threads:[~2011-07-27 22:15 UTC|newest]
Thread overview: 11+ 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 21:44 ` Andi Kleen
2011-06-29 21:03 ` Theodore Ts'o
2011-07-27 21:08 ` Christoph Hellwig
2011-07-27 21:14 ` Andrew Morton
2011-07-27 22:15 ` Jeff Moyer [this message]
2011-07-28 22:09 ` 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=x49vcuns73a.fsf@segfault.boston.devel.redhat.com \
--to=jmoyer@redhat.com \
--cc=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 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).