From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: David Howells <dhowells@redhat.com>,
Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Nicolas Dichtel <nicolas.dichtel@6wind.com>,
raven@themaw.net, Christian Brauner <christian@brauner.io>,
keyrings@vger.kernel.org, linux-usb@vger.kernel.org,
linux-block <linux-block@vger.kernel.org>,
LSM List <linux-security-module@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 11/10] pipe: Add fsync() support [ver #2]
Date: Sat, 2 Nov 2019 16:09:55 -0700 [thread overview]
Message-ID: <CAHk-=wgPQutQ8d8kUCvAFi+hfNWgaNLiZPkbg-GXY2DCtD-Z5Q@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wgzRU9RjkZG0L9_yrnFN69REkrSokTQOGZMUkvdispvuQ@mail.gmail.com>
On Sat, Nov 2, 2019 at 4:02 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> But I don't think anybody actually _did_ any of that. But that's
> basically the argument for the three splice operations:
> write/vmsplice/splice(). Which one you use depends on the lifetime and
> the source of your data. write() is obviously for the copy case (the
> source data might not be stable), while splice() is for the "data from
> another source", and vmsplace() is "data is from stable data in my
> vm".
Btw, it's really worth noting that "splice()" and friends are from a
more happy-go-lucky time when we were experimenting with new
interfaces, and in a day and age when people thought that interfaces
like "sendpage()" and zero-copy and playing games with the VM was a
great thing to do.
It turns out that VM games are almost always more expensive than just
copying the data in the first place, but hey, people didn't know that,
and zero-copy was seen a big deal.
The reality is that almost nobody uses splice and vmsplice at all, and
they have been a much bigger headache than they are worth. If I could
go back in time and not do them, I would. But there have been a few
very special uses that seem to actually like the interfaces.
But it's entirely possible that we should kill vmsplice() (likely by
just implementing the semantics as "write()") because it's not common
enough to have the complexity.
Linus
next prev parent reply other threads:[~2019-11-02 23:10 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-23 20:17 [RFC PATCH 00/10] pipe: Notification queue preparation [ver #2] David Howells
2019-10-23 20:17 ` [RFC PATCH 01/10] pipe: Reduce #inclusion of pipe_fs_i.h " David Howells
2019-10-23 20:17 ` [RFC PATCH 02/10] Remove the nr_exclusive argument from __wake_up_sync_key() " David Howells
2019-10-23 20:17 ` [RFC PATCH 03/10] Add wake_up_interruptible_sync_poll_locked() " David Howells
2019-10-23 20:17 ` [RFC PATCH 04/10] pipe: Use head and tail pointers for the ring, not cursor and length " David Howells
2019-10-26 14:58 ` [pipe] 6567a02d20: BUG:kernel_NULL_pointer_dereference,address kernel test robot
2019-10-27 14:03 ` [RFC PATCH 04/10] pipe: Use head and tail pointers for the ring, not cursor and length [ver #2] Linus Torvalds
2019-10-30 16:19 ` Ilya Dryomov
2019-10-30 20:35 ` Rasmus Villemoes
2019-10-30 22:16 ` Ilya Dryomov
2019-10-30 22:38 ` Rasmus Villemoes
2019-10-31 15:11 ` David Howells
2019-10-31 15:57 ` Ilya Dryomov
2019-11-01 14:53 ` David Howells
2019-10-31 14:57 ` David Howells
2019-11-03 11:17 ` Matthew Wilcox
2019-12-06 21:47 ` Johannes Hirte
2019-12-06 22:14 ` Linus Torvalds
2019-12-07 0:00 ` Johannes Hirte
2019-12-07 1:03 ` Linus Torvalds
2019-12-08 17:56 ` Johannes Hirte
2019-12-08 18:10 ` Linus Torvalds
2019-12-07 6:47 ` Linus Torvalds
2019-12-06 22:15 ` David Howells
2019-10-23 20:17 ` [RFC PATCH 05/10] pipe: Allow pipes to have kernel-reserved slots " David Howells
2019-10-23 20:18 ` [RFC PATCH 06/10] pipe: Advance tail pointer inside of wait spinlock in pipe_read() " David Howells
2019-10-23 20:18 ` [RFC PATCH 07/10] pipe: Conditionalise wakeup " David Howells
2019-10-27 15:57 ` Konstantin Khlebnikov
2019-10-31 15:21 ` David Howells
2019-10-31 16:38 ` David Howells
2019-11-03 11:04 ` Konstantin Khlebnikov
2019-10-23 20:18 ` [RFC PATCH 08/10] pipe: Rearrange sequence in pipe_write() to preallocate slot " David Howells
2019-10-23 20:18 ` [RFC PATCH 09/10] pipe: Remove redundant wakeup from pipe_write() " David Howells
2019-10-23 20:18 ` [RFC PATCH 10/10] pipe: Check for ring full inside of the spinlock in " David Howells
2019-10-24 10:32 ` [RFC PATCH 04/10] pipe: Use head and tail pointers for the ring, not cursor and length " David Howells
2019-10-24 13:14 ` [RFC PATCH 00/10] pipe: Notification queue preparation " Peter Zijlstra
2019-10-24 16:57 ` [RFC PATCH 11/10] pipe: Add fsync() support " David Howells
2019-10-24 21:29 ` Linus Torvalds
2019-10-25 8:34 ` David Howells
2019-10-27 15:22 ` Christoph Hellwig
2019-10-27 16:04 ` Konstantin Khlebnikov
2019-10-31 15:13 ` David Howells
2019-10-31 15:15 ` David Howells
2019-11-02 18:53 ` Linus Torvalds
2019-11-02 19:34 ` David Howells
2019-11-02 20:31 ` Andy Lutomirski
2019-11-02 22:03 ` Linus Torvalds
2019-11-02 22:09 ` Linus Torvalds
2019-11-02 22:30 ` Andy Lutomirski
2019-11-02 23:02 ` Linus Torvalds
2019-11-02 23:09 ` Linus Torvalds [this message]
2019-11-02 23:14 ` Andy Lutomirski
2019-11-03 12:02 ` Konstantin Khlebnikov
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