From: Pedro Falcato <pfalcato@suse•de>
To: Linus Torvalds <torvalds@linux-foundation•org>,
Askar Safin <safinaskar@gmail•com>
Cc: akpm@linux-foundation•org, axboe@kernel•dk, brauner@kernel•org,
david@kernel•org, dhowells@redhat•com, hch@infradead•org,
jack@suse•cz, linux-api@vger•kernel.org,
linux-fsdevel@vger•kernel.org, linux-kernel@vger•kernel.org,
linux-mm@kvack•org, miklos@szeredi•hu, netdev@vger•kernel.org,
patches@lists•linux.dev, viro@zeniv•linux.org.uk,
willy@infradead•org
Subject: Re: [PATCH 0/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2
Date: Tue, 2 Jun 2026 23:41:40 +0100 [thread overview]
Message-ID: <ah9Yle5pd6mD9Ugr@pedro-suse.lan> (raw)
In-Reply-To: <CAHk-=wiAqf0PdZ4AKj_4riUnnEb=g_ZNPkLnXrByA9BBHYiFRg@mail.gmail.com>
On Tue, Jun 02, 2026 at 03:06:07PM -0700, Linus Torvalds wrote:
> On Tue, 2 Jun 2026 at 14:37, Pedro Falcato <pfalcato@suse•de> wrote:
> >
> > Well, that's most definitely part of my patch. Also, you cannot outright
> > remove splice() functionality
>
> That isn't what Askar's patch ever did.
>
> You apparently didn't even read it.
Well, I was replying to Askar's new idea to remove pagecache-to-pipe splice,
which is what he suggested. And directly intersects with my sysctl-to-disable-splice
patch.
> Honestly, I think you are the one out of line here.
>
> Askar did something I suggested years ago, and didn't remove any functionality.
>
> It just changes vmsplice to be a copying model (one of the directions
> already was). It doesn't change regular splice at all.
>
> And yes, it has the potential to be a visible behavior difference - if
> some insane user uses vmsplice and then modifies the buffer
> *afterwards*, then that would be semantically different between a
> zero-copy and a normal copy.
>
> But that would be insane behavior, and was never really reliable
> anyway even with zero-copy (ie subsequent writes to user space buffers
> would potentially do COW breaking based purely on timing and memory
> pressure etc, so anybody who relied on it being visible wasn't goign
> to get it realiably anyway)
>
> Perhaps more importantly, it has the potential to change performance -
> zero-copy *can* be a performance win, although typically it really
> doesn't tend to be (looking up the page mapping is often slower than
> copying).
>
> I would expect it to be very clear in trivial benchmarks that aren't
> actually real loads. And probably not visible anywhere else.
Yes, vmsplice() sucks, and we know it. Hopefully no one else will see the
difference. I don't think we can say the same for splice(), though.
> Trying to make it look like Askar is the problem is only making you look worse.
To be clear, I don't think Askar is the (or a) problem. I'm glad he's
contributing, and getting rid of bad kernel interfaces is always nice. I was
just a little frustrated with a parallel splice-related-unscrew patch.
(Askar, if I was too hostile, I do sincerely apologize.)
--
Pedro
next prev parent reply other threads:[~2026-06-02 22:41 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-31 1:01 [PATCH 0/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2 Askar Safin
2026-05-31 1:01 ` [PATCH 1/3] tee: fs/splice.c: remove unused parameter "flags" from "link_pipe" Askar Safin
2026-05-31 1:01 ` [PATCH 2/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2 Askar Safin
2026-06-03 20:56 ` Stefan Metzmacher
2026-06-03 21:17 ` Askar Safin
2026-06-04 9:06 ` David Laight
2026-06-04 14:17 ` Linus Torvalds
2026-06-04 17:38 ` David Laight
2026-06-04 19:30 ` Linus Torvalds
2026-06-04 21:32 ` David Laight
2026-06-04 21:42 ` Linus Torvalds
2026-06-05 9:32 ` Florian Weimer
2026-06-05 15:54 ` Linus Torvalds
2026-06-05 16:27 ` Linus Torvalds
2026-06-05 16:30 ` Florian Weimer
2026-06-05 17:12 ` Linus Torvalds
2026-06-06 9:16 ` David Laight
2026-06-05 1:57 ` Nathan Chancellor
2026-06-05 8:23 ` David Laight
2026-06-04 23:25 ` Askar Safin
2026-06-05 11:02 ` Mark Brown
2026-06-05 16:02 ` Linus Torvalds
2026-06-05 16:26 ` Mark Brown
2026-06-05 17:21 ` David Hildenbrand (Arm)
2026-05-31 1:01 ` [PATCH 3/3] splice: remove PIPE_BUF_FLAG_GIFT Askar Safin
2026-05-31 8:54 ` [PATCH 0/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2 Pedro Falcato
2026-05-31 19:01 ` David Hildenbrand (Arm)
2026-05-31 21:21 ` Askar Safin
2026-06-01 16:16 ` Christian Brauner
2026-06-02 21:12 ` Askar Safin
2026-06-02 21:37 ` Pedro Falcato
2026-06-02 22:06 ` Linus Torvalds
2026-06-02 22:41 ` Pedro Falcato [this message]
2026-06-02 23:07 ` Askar Safin
2026-06-02 22:54 ` Askar Safin
2026-06-03 0:05 ` Linus Torvalds
2026-06-03 1:08 ` Askar Safin
2026-06-03 3:51 ` Andy Lutomirski
2026-06-03 4:20 ` Linus Torvalds
2026-06-03 6:45 ` Christian Brauner
2026-06-03 13:40 ` Christian Brauner
2026-06-03 15:26 ` Linus Torvalds
2026-06-03 18:10 ` Andy Lutomirski
2026-06-03 18:28 ` Linus Torvalds
2026-06-03 19:22 ` David Howells
2026-06-03 19:59 ` Linus Torvalds
2026-06-03 21:31 ` Andy Lutomirski
2026-06-03 21:36 ` Linus Torvalds
2026-06-03 21:38 ` Linus Torvalds
2026-06-03 22:23 ` Andy Lutomirski
2026-06-03 22:53 ` Linus Torvalds
2026-06-05 15:15 ` Stefan Metzmacher
2026-06-05 15:58 ` Linus Torvalds
2026-06-03 22:43 ` Askar Safin
2026-06-03 22:49 ` Andy Lutomirski
2026-06-03 23:00 ` Askar Safin
2026-06-04 0:01 ` Linus Torvalds
2026-06-03 18:12 ` Jakub Kicinski
2026-06-05 9:43 ` Stefan Metzmacher
2026-06-05 12:19 ` David Laight
2026-06-05 15:20 ` Stefan Metzmacher
2026-06-06 10:22 ` David Laight
2026-06-03 11:43 ` Pedro Falcato
2026-06-03 18:14 ` Jakub Kicinski
2026-06-01 3:11 ` Andy Lutomirski
2026-06-01 15:36 ` Matthew Wilcox
2026-06-01 15:50 ` Linus Torvalds
2026-06-01 16:17 ` Christian Brauner
2026-06-01 16:22 ` Linus Torvalds
2026-06-03 19:24 ` David Howells
2026-06-01 16:23 ` Christian Brauner
2026-06-01 17:17 ` Linus Torvalds
2026-06-01 17:33 ` Al Viro
2026-06-01 20:04 ` Steven Rostedt
2026-06-02 0:28 ` Andrew Morton
2026-06-02 8:25 ` David Hildenbrand (Arm)
2026-06-02 18:44 ` Eric Biggers
2026-06-03 7:50 ` David Hildenbrand (Arm)
2026-06-04 6:32 ` Willy Tarreau
2026-06-04 14:31 ` Linus Torvalds
2026-06-04 15:53 ` Willy Tarreau
2026-06-04 15:58 ` Linus Torvalds
2026-06-04 16:15 ` Willy Tarreau
2026-06-05 15:41 ` Willy Tarreau
2026-06-05 20:54 ` The 8472
2026-06-04 15:53 ` Andy Lutomirski
2026-06-04 16:09 ` Willy Tarreau
2026-06-04 17:25 ` Andy Lutomirski
2026-06-03 9:57 ` Miklos Szeredi
2026-06-05 8:35 ` Collin Funk
2026-06-04 0:45 ` [PATCH 0/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2 Askar Safin
2026-06-04 1:52 ` Linus Torvalds
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