From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
To: David Howells <dhowells@redhat.com>, torvalds@linux-foundation.org
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Peter Zijlstra <peterz@infradead.org>,
nicolas.dichtel@6wind.com, raven@themaw.net,
Christian Brauner <christian@brauner.io>,
keyrings@vger.kernel.org, linux-usb@vger.kernel.org,
linux-block@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 07/10] pipe: Conditionalise wakeup in pipe_read() [ver #2]
Date: Sun, 27 Oct 2019 18:57:35 +0300 [thread overview]
Message-ID: <fe167a90-1503-7ca2-4150-eeffd5cb1378@yandex-team.ru> (raw)
In-Reply-To: <157186189069.3995.10292601951655075484.stgit@warthog.procyon.org.uk>
On 23/10/2019 23.18, David Howells wrote:
> Only do a wakeup in pipe_read() if we made space in a completely full
> buffer. The producer shouldn't be waiting on pipe->wait otherwise.
We could go further and wakeup writer only when at least half of buffer is empty.
This gives better batching and reduces rate of context switches.
https://lore.kernel.org/lkml/157219118016.7078.16223055699799396042.stgit@buzz/T/#u
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
>
> fs/pipe.c | 15 ++++++---------
> 1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/fs/pipe.c b/fs/pipe.c
> index 1274305772fb..e3a8f10750c9 100644
> --- a/fs/pipe.c
> +++ b/fs/pipe.c
> @@ -327,11 +327,13 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
> spin_lock_irq(&pipe->wait.lock);
> tail++;
> pipe_commit_read(pipe, tail);
> - do_wakeup = 0;
> - wake_up_interruptible_sync_poll_locked(
> - &pipe->wait, EPOLLOUT | EPOLLWRNORM);
> + do_wakeup = 1;
> + if (head - (tail - 1) == pipe->max_usage)
> + wake_up_interruptible_sync_poll_locked(
> + &pipe->wait, EPOLLOUT | EPOLLWRNORM);
> spin_unlock_irq(&pipe->wait.lock);
> - kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
> + if (head - (tail - 1) == pipe->max_usage)
> + kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
> }
> total_len -= chars;
> if (!total_len)
> @@ -360,11 +362,6 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
> ret = -ERESTARTSYS;
> break;
> }
> - if (do_wakeup) {
> - wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
> - kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
> - do_wakeup = 0;
> - }
> pipe_wait(pipe);
> }
> __pipe_unlock(pipe);
>
>
next prev parent reply other threads:[~2019-10-27 15:57 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 [this message]
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
2019-11-02 23:14 ` Andy Lutomirski
2019-11-03 12:02 ` Konstantin Khlebnikov
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