From: Anton Altaparmakov <aia21@cam.ac.uk>
To: Anand Avati <avati@gluster.org>
Cc: Jeff Moyer <jmoyer@redhat.com>,
linux-arch@vger.kernel.org, linux-aio@kvack.org,
linux-nfs@vger.kernel.org,
Volker Lendecke <Volker.Lendecke@sernet.de>,
"Theodore Ts'o" <tytso@mit.edu>,
linux-mm@kvack.org,
"fuse-devel@lists.sourceforge.net"
<fuse-devel@lists.sourceforge.net>,
linux-api@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Christoph Hellwig <hch@infradead.org>, Tejun Heo <tj@kernel.org>,
Milosz Tanski <milosz@adfin.com>,
linux-fsdevel@vger.kernel.org,
Michael Kerrisk <mtk.manpages@gmail.com>,
ceph-devel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
ocfs2-devel@oss.oracle.com, Mel Gorman <mgorman@suse.de>
Subject: Re: [fuse-devel] [PATCH v5 7/7] add a flag for per-operation O_DSYNC semantics
Date: Fri, 7 Nov 2014 08:43:00 +0200 [thread overview]
Message-ID: <B92AEADD-B22C-4A4A-B64D-96E8869D3282@cam.ac.uk> (raw)
In-Reply-To: <CAFboF2y2skt=H4crv54shfnXOmz23W-shYWtHWekK8ZUDkfP=A@mail.gmail.com>
Hi,
> On 7 Nov 2014, at 07:52, Anand Avati <avati@gluster.org> wrote:
> On Thu, Nov 6, 2014 at 8:22 PM, Anton Altaparmakov <aia21@cam.ac.uk> wrote:
> > On 7 Nov 2014, at 01:46, Jeff Moyer <jmoyer@redhat.com> wrote:
> > Minor nit, but I'd rather read something that looks like this:
> >
> > if (type == READ && (flags & RWF_NONBLOCK))
> > return -EAGAIN;
> > else if (type == WRITE && (flags & RWF_DSYNC))
> > return -EINVAL;
>
> But your version is less logically efficient for the case where "type == READ" is true and "flags & RWF_NONBLOCK" is false because your version then has to do the "if (type == WRITE" check before discovering it does not need to take that branch either, whilst the original version does not have to do such a test at all.
>
> Seriously?
Of course seriously.
> Just focus on the code readability/maintainability which makes the code most easily understood/obvious to a new pair of eyes, and leave such micro-optimizations to the compiler..
The original version is more readable (IMO) and this is not a micro-optimization. It is people like you who are responsible for the fact that we need faster and faster computers to cope with the inefficient/poor code being written more and more...
And I really wouldn't hedge my bets on gcc optimizing something like that. The amount of crap assembly produced from gcc that I have seen over the years suggests that it is quite likely it will make a hash of it instead...
Best regards,
Anton
> Thanks
--
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
University of Cambridge Information Services, Roger Needham Building
7 JJ Thomson Avenue, Cambridge, CB3 0RB, UK
WARNING: multiple messages have this Message-ID (diff)
From: Anton Altaparmakov <aia21@cam.ac.uk>
To: Anand Avati <avati@gluster.org>
Cc: Jeff Moyer <jmoyer@redhat.com>,
linux-arch@vger.kernel.org, linux-aio@kvack.org,
linux-nfs@vger.kernel.org,
Volker Lendecke <Volker.Lendecke@sernet.de>,
Theodore Ts'o <tytso@mit.edu>,
linux-mm@kvack.org,
"fuse-devel@lists.sourceforge.net"
<fuse-devel@lists.sourceforge.net>,
linux-api@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Christoph Hellwig <hch@infradead.org>, Tejun Heo <tj@kernel.org>,
Milosz Tanski <milosz@adfin.com>,
linux-fsdevel@vger.kernel.org,
Michael Kerrisk <mtk.manpages@gmail.com>,
ceph-devel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
ocfs2-devel@oss.oracle.com, Mel Gorman <mgorman@suse.de>
Subject: [Ocfs2-devel] [fuse-devel] [PATCH v5 7/7] add a flag for per-operation O_DSYNC semantics
Date: Fri, 7 Nov 2014 08:43:00 +0200 [thread overview]
Message-ID: <B92AEADD-B22C-4A4A-B64D-96E8869D3282@cam.ac.uk> (raw)
In-Reply-To: <CAFboF2y2skt=H4crv54shfnXOmz23W-shYWtHWekK8ZUDkfP=A@mail.gmail.com>
Hi,
> On 7 Nov 2014, at 07:52, Anand Avati <avati@gluster.org> wrote:
> On Thu, Nov 6, 2014 at 8:22 PM, Anton Altaparmakov <aia21@cam.ac.uk> wrote:
> > On 7 Nov 2014, at 01:46, Jeff Moyer <jmoyer@redhat.com> wrote:
> > Minor nit, but I'd rather read something that looks like this:
> >
> > if (type == READ && (flags & RWF_NONBLOCK))
> > return -EAGAIN;
> > else if (type == WRITE && (flags & RWF_DSYNC))
> > return -EINVAL;
>
> But your version is less logically efficient for the case where "type == READ" is true and "flags & RWF_NONBLOCK" is false because your version then has to do the "if (type == WRITE" check before discovering it does not need to take that branch either, whilst the original version does not have to do such a test at all.
>
> Seriously?
Of course seriously.
> Just focus on the code readability/maintainability which makes the code most easily understood/obvious to a new pair of eyes, and leave such micro-optimizations to the compiler..
The original version is more readable (IMO) and this is not a micro-optimization. It is people like you who are responsible for the fact that we need faster and faster computers to cope with the inefficient/poor code being written more and more...
And I really wouldn't hedge my bets on gcc optimizing something like that. The amount of crap assembly produced from gcc that I have seen over the years suggests that it is quite likely it will make a hash of it instead...
Best regards,
Anton
> Thanks
--
Anton Altaparmakov <aia21@cam.ac.uk> (replace at with @)
University of Cambridge Information Services, Roger Needham Building
7 JJ Thomson Avenue, Cambridge, CB3 0RB, UK
WARNING: multiple messages have this Message-ID (diff)
From: Anton Altaparmakov <aia21@cam.ac.uk>
To: Anand Avati <avati@gluster.org>
Cc: Jeff Moyer <jmoyer@redhat.com>,
linux-arch@vger.kernel.org, linux-aio@kvack.org,
linux-nfs@vger.kernel.org,
Volker Lendecke <Volker.Lendecke@sernet.de>,
Theodore Ts'o <tytso@mit.edu>,
linux-mm@kvack.org,
"fuse-devel@lists.sourceforge.net"
<fuse-devel@lists.sourceforge.net>,
linux-api@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Christoph Hellwig <hch@infradead.org>, Tejun Heo <tj@kernel.org>,
Milosz Tanski <milosz@adfin.com>,
linux-fsdevel@vger.kernel.org,
Michael Kerrisk <mtk.manpages@gmail.com>,
ceph-devel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
ocfs2-devel@oss.oracle.com, Mel Gorman <mgorman@suse.de>
Subject: Re: [fuse-devel] [PATCH v5 7/7] add a flag for per-operation O_DSYNC semantics
Date: Fri, 7 Nov 2014 08:43:00 +0200 [thread overview]
Message-ID: <B92AEADD-B22C-4A4A-B64D-96E8869D3282@cam.ac.uk> (raw)
In-Reply-To: <CAFboF2y2skt=H4crv54shfnXOmz23W-shYWtHWekK8ZUDkfP=A@mail.gmail.com>
Hi,
> On 7 Nov 2014, at 07:52, Anand Avati <avati@gluster.org> wrote:
> On Thu, Nov 6, 2014 at 8:22 PM, Anton Altaparmakov <aia21@cam.ac.uk> wrote:
> > On 7 Nov 2014, at 01:46, Jeff Moyer <jmoyer@redhat.com> wrote:
> > Minor nit, but I'd rather read something that looks like this:
> >
> > if (type == READ && (flags & RWF_NONBLOCK))
> > return -EAGAIN;
> > else if (type == WRITE && (flags & RWF_DSYNC))
> > return -EINVAL;
>
> But your version is less logically efficient for the case where "type == READ" is true and "flags & RWF_NONBLOCK" is false because your version then has to do the "if (type == WRITE" check before discovering it does not need to take that branch either, whilst the original version does not have to do such a test at all.
>
> Seriously?
Of course seriously.
> Just focus on the code readability/maintainability which makes the code most easily understood/obvious to a new pair of eyes, and leave such micro-optimizations to the compiler..
The original version is more readable (IMO) and this is not a micro-optimization. It is people like you who are responsible for the fact that we need faster and faster computers to cope with the inefficient/poor code being written more and more...
And I really wouldn't hedge my bets on gcc optimizing something like that. The amount of crap assembly produced from gcc that I have seen over the years suggests that it is quite likely it will make a hash of it instead...
Best regards,
Anton
> Thanks
--
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
University of Cambridge Information Services, Roger Needham Building
7 JJ Thomson Avenue, Cambridge, CB3 0RB, UK
--
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next prev parent reply other threads:[~2014-11-07 6:43 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-05 21:14 [PATCH v5 0/7] vfs: Non-blockling buffered fs read (page cache only) Milosz Tanski
2014-11-05 21:14 ` [PATCH v5 1/7] vfs: Prepare for adding a new preadv/pwritev with user flags Milosz Tanski
2014-11-05 21:14 ` Milosz Tanski
2014-11-05 21:14 ` [PATCH v5 2/7] vfs: Define new syscalls preadv2,pwritev2 Milosz Tanski
2014-11-05 21:14 ` Milosz Tanski
2014-11-05 21:14 ` Milosz Tanski
2014-11-06 23:25 ` Jeff Moyer
2014-11-06 23:25 ` Jeff Moyer
2014-11-07 16:28 ` Milosz Tanski
2014-11-07 16:28 ` Milosz Tanski
2014-11-05 21:14 ` [PATCH v5 3/7] x86: wire up preadv2 and pwritev2 Milosz Tanski
2014-11-05 21:14 ` Milosz Tanski
2014-11-05 21:14 ` [PATCH v5 4/7] vfs: RWF_NONBLOCK flag for preadv2 Milosz Tanski
2014-11-05 21:14 ` Milosz Tanski
2014-11-05 21:14 ` [Ocfs2-devel] " Milosz Tanski
2014-11-05 21:14 ` Milosz Tanski
2014-11-10 16:07 ` Sage Weil
2014-11-10 16:07 ` Sage Weil
2014-11-10 16:07 ` [Ocfs2-devel] " Sage Weil
2014-11-10 16:07 ` Sage Weil
2014-11-05 21:14 ` [PATCH v5 5/7] xfs: add RWF_NONBLOCK support Milosz Tanski
2014-11-05 21:14 ` Milosz Tanski
2014-11-05 21:14 ` [PATCH v5 6/7] fs: pass iocb to generic_write_sync Milosz Tanski
2014-11-05 21:14 ` [Cluster-devel] " Milosz Tanski
2014-11-05 21:14 ` Milosz Tanski
2014-11-06 10:18 ` [Cluster-devel] " Steven Whitehouse
2014-11-06 10:18 ` Steven Whitehouse
2014-11-06 10:18 ` Steven Whitehouse
2014-11-06 10:52 ` [Linux-NTFS-Dev] " Anton Altaparmakov
2014-11-06 10:52 ` [Cluster-devel] " Anton Altaparmakov
2014-11-06 10:52 ` Anton Altaparmakov
2014-11-06 16:14 ` Milosz Tanski
2014-11-06 16:14 ` [Cluster-devel] " Milosz Tanski
2014-11-06 16:14 ` Milosz Tanski
2014-11-06 12:04 ` Jan Kara
2014-11-06 12:04 ` [Cluster-devel] " Jan Kara
2014-11-06 12:04 ` Jan Kara
2014-11-05 21:14 ` [PATCH v5 7/7] fs: add a flag for per-operation O_DSYNC semantics Milosz Tanski
2014-11-05 21:14 ` Milosz Tanski
2014-11-05 21:14 ` [Ocfs2-devel] " Milosz Tanski
2014-11-05 21:14 ` Milosz Tanski
2014-11-06 23:46 ` Jeff Moyer
2014-11-06 23:46 ` [Ocfs2-devel] " Jeff Moyer
2014-11-06 23:46 ` Jeff Moyer
2014-11-07 4:22 ` [PATCH v5 7/7] " Anton Altaparmakov
2014-11-07 4:22 ` Anton Altaparmakov
2014-11-07 4:22 ` [Ocfs2-devel] " Anton Altaparmakov
2014-11-07 4:22 ` Anton Altaparmakov
2014-11-07 5:52 ` [fuse-devel] " Anand Avati
2014-11-07 5:52 ` [Ocfs2-devel] " Anand Avati
2014-11-07 6:43 ` Anton Altaparmakov [this message]
2014-11-07 6:43 ` Anton Altaparmakov
2014-11-07 6:43 ` [Ocfs2-devel] " Anton Altaparmakov
2014-11-07 14:21 ` Roger Willcocks
2014-11-07 14:21 ` Roger Willcocks
2014-11-07 14:21 ` [Ocfs2-devel] " Roger Willcocks
2014-11-07 14:21 ` Roger Willcocks
2014-11-07 14:21 ` Roger Willcocks
2014-11-07 19:58 ` Milosz Tanski
2014-11-07 19:58 ` [Ocfs2-devel] " Milosz Tanski
2014-11-07 19:58 ` Milosz Tanski
2014-11-10 16:07 ` [PATCH v5 7/7] fs: " Sage Weil
2014-11-10 16:07 ` [Ocfs2-devel] " Sage Weil
2014-11-10 16:07 ` Sage Weil
2014-11-06 7:56 ` [PATCH v5 0/7] vfs: Non-blockling buffered fs read (page cache only) Christoph Hellwig
2014-11-06 7:56 ` Christoph Hellwig
2014-11-06 15:46 ` Milosz Tanski
2014-11-06 15:46 ` Milosz Tanski
2014-11-06 15:44 ` [PATCH v2 1/2] Add preadv2/pwritev2 documentation Milosz Tanski
2014-11-06 15:44 ` Milosz Tanski
2014-11-06 15:44 ` [PATCH v2 2/2] RWF_ODSYNC flag for pwritev2 Milosz Tanski
2014-11-06 15:44 ` Milosz Tanski
2014-11-06 16:16 ` [PATCH v5 0/7] vfs: Non-blockling buffered fs read (page cache only) Milosz Tanski
2014-11-06 16:16 ` Milosz Tanski
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