From: Oleg Nesterov <oleg@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: WangYuli <wangyuli@uniontech.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Christian Brauner <brauner@kernel.org>
Subject: Re: [RESEND PATCH] fs/pipe: Introduce a check to skip sleeping processes during pipe read/write
Date: Thu, 26 Dec 2024 21:57:46 +0100 [thread overview]
Message-ID: <20241226205746.GC11118@redhat.com> (raw)
In-Reply-To: <CAHk-=whRnW3e3g5PkEtH6geVVYZO2MPUH4ZV5a=khePC9evY4g@mail.gmail.com>
On 12/26, Linus Torvalds wrote:
>
> [ Ugh, removed the crazy cc list with tons of old addresses ]
thanks.
> So the optimization may be valid
I don't think so, see my initial reply.
unlike wait_event(), __pollwait() + the head/tail checks in pipe_poll()
doesn't have the necessary barriers (at least in theory) afaics. Between
add_wait_queue()->list_add() and LOAD(head/tail).
> (the config option definitely is
> not), but I think it needs to be explained much better.
>
> I end up being very nervous about this code because we've had bugs in
> this area, exactly because people optimize this code for the unixbench
> pipe benchmark.
Agreed!
Oleg.
next prev parent reply other threads:[~2024-12-26 20:58 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-25 9:42 [RESEND PATCH] fs/pipe: Introduce a check to skip sleeping processes during pipe read/write WangYuli
2024-12-25 13:30 ` Andy Shevchenko
2024-12-25 13:53 ` Kent Overstreet
2024-12-25 16:04 ` Mateusz Guzik
2024-12-25 16:32 ` Kent Overstreet
2024-12-25 17:22 ` Mateusz Guzik
2024-12-25 17:41 ` Kent Overstreet
2024-12-25 15:42 ` WangYuli
2024-12-25 16:00 ` Willy Tarreau
2024-12-25 16:32 ` WangYuli
2024-12-25 16:56 ` Willy Tarreau
2024-12-26 16:00 ` Oleg Nesterov
2024-12-26 19:02 ` Linus Torvalds
2024-12-26 20:11 ` Oleg Nesterov
2024-12-26 20:29 ` Linus Torvalds
2024-12-26 20:57 ` Oleg Nesterov [this message]
2024-12-27 15:54 ` Oleg Nesterov
2024-12-27 16:43 ` Oleg Nesterov
2024-12-27 18:39 ` Manfred Spraul
2024-12-28 14:32 ` Oleg Nesterov
2024-12-28 15:22 ` Oleg Nesterov
2024-12-28 16:32 ` Oleg Nesterov
2024-12-28 18:53 ` Manfred Spraul
2024-12-29 11:54 ` Oleg Nesterov
2024-12-28 16:45 ` Manfred Spraul
2024-12-29 11:57 ` Oleg Nesterov
2024-12-29 12:41 ` Manfred Spraul
2024-12-29 13:05 ` Oleg Nesterov
2024-12-29 13:13 ` Oleg Nesterov
2024-12-29 19:54 ` Manfred Spraul
2024-12-30 15:38 ` Oleg Nesterov
2024-12-31 11:14 ` Manfred Spraul
2024-12-31 19:38 ` Linus Torvalds
2024-12-31 20:24 ` Oleg Nesterov
2024-12-31 22:31 ` Linus Torvalds
2025-01-02 13:57 ` Oleg Nesterov
2025-01-04 21:15 ` RFC: Checkpatch: Introduce list of functions that need memory barriers Manfred Spraul
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