From: David Howells <dhowells@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: dhowells@redhat.com, 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 00/11] pipe: Notification queue preparation [ver #3]
Date: Fri, 01 Nov 2019 22:05:26 +0000 [thread overview]
Message-ID: <13964.1572645926@warthog.procyon.org.uk> (raw)
In-Reply-To: <CAHk-=wjqx4j2vqg-tAwthNP1gcAcj1x4B7sq6Npbi8QJTUMd-A@mail.gmail.com>
Linus Torvalds <torvalds@linux-foundation.org> wrote:
> Side note: we have a couple of cases where I don't think we should use
> the "sync" version at all.
>
> Both pipe_read() and pipe_write() have that
>
> if (do_wakeup) {
> wake_up_interruptible_sync_poll(&pipe->wait, ...
>
> code at the end, outside the loop. But those two wake-ups aren't
> actually synchronous.
Changing those to non-sync:
BENCHMARK BEST TOTAL BYTES AVG BYTES STDDEV
=============== =============== =============== =============== ===============
pipe 305816126 36255936983 302132808 8880788
splice 282402106 27102249370 225852078 210033443
vmsplice 440022611 48896995196 407474959 59906438
Changing the others in pipe_read() and pipe_write() too:
pipe 305609682 36285967942 302383066 7415744
splice 282475690 27891475073 232428958 201687522
vmsplice 451458280 51949421503 432911845 34925242
The cumulative patch is attached below. I'm not sure how well this should
make a difference with my benchmark programs since each thread can run on its
own CPU.
David
---
diff --git a/fs/pipe.c b/fs/pipe.c
index 9cd5cbef9552..c5e3765465f0 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -332,7 +332,7 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
do_wakeup = 1;
wake = head - (tail - 1) == pipe->max_usage / 2;
if (wake)
- wake_up_interruptible_sync_poll_locked(
+ wake_up_locked_poll(
&pipe->wait, EPOLLOUT | EPOLLWRNORM);
spin_unlock_irq(&pipe->wait.lock);
if (wake)
@@ -371,7 +371,7 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
/* Signal writers asynchronously that there is more room. */
if (do_wakeup) {
- wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
+ wake_up_interruptible_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
}
if (ret > 0)
@@ -477,7 +477,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
* syscall merging.
* FIXME! Is this really true?
*/
- wake_up_interruptible_sync_poll_locked(
+ wake_up_locked_poll(
&pipe->wait, EPOLLIN | EPOLLRDNORM);
spin_unlock_irq(&pipe->wait.lock);
@@ -531,7 +531,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
out:
__pipe_unlock(pipe);
if (do_wakeup) {
- wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
+ wake_up_interruptible_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
}
if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
next prev parent reply other threads:[~2019-11-01 22:05 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-01 17:34 [RFC PATCH 00/11] pipe: Notification queue preparation [ver #3] David Howells
2019-11-01 17:34 ` [RFC PATCH 01/11] pipe: Reduce #inclusion of pipe_fs_i.h " David Howells
2019-11-01 17:34 ` [RFC PATCH 02/11] Remove the nr_exclusive argument from __wake_up_sync_key() " David Howells
2019-11-01 17:34 ` [RFC PATCH 03/11] Add wake_up_interruptible_sync_poll_locked() " David Howells
2019-11-01 17:34 ` [RFC PATCH 04/11] pipe: Use head and tail pointers for the ring, not cursor and length " David Howells
2019-11-07 9:03 ` [pipe] d60337eff1: phoronix-test-suite.noise-level.0.activity_level 144.0% improvement lkp report check
2019-11-07 16:51 ` Linus Torvalds
2019-11-07 17:42 ` David Howells
2019-11-10 3:13 ` [pipe] d60337eff1: BUG:kernel_NULL_pointer_dereference,address kernel test robot
2019-11-15 13:28 ` David Howells
2019-11-15 16:22 ` David Howells
2019-11-18 7:53 ` [LKP] " kernel test robot
2019-11-01 17:34 ` [RFC PATCH 05/11] pipe: Allow pipes to have kernel-reserved slots [ver #3] David Howells
2019-11-01 17:34 ` [RFC PATCH 06/11] pipe: Advance tail pointer inside of wait spinlock in pipe_read() " David Howells
2019-11-01 17:35 ` [RFC PATCH 07/11] pipe: Conditionalise wakeup " David Howells
2019-11-01 17:35 ` [RFC PATCH 08/11] pipe: Rearrange sequence in pipe_write() to preallocate slot " David Howells
2019-11-01 17:35 ` [RFC PATCH 09/11] pipe: Remove redundant wakeup from pipe_write() " David Howells
2019-11-01 17:35 ` [RFC PATCH 10/11] pipe: Check for ring full inside of the spinlock in " David Howells
2019-11-01 17:35 ` [RFC PATCH 11/11] pipe: Increase the writer-wakeup threshold to reduce context-switch count " David Howells
2019-11-01 19:24 ` [RFC PATCH 00/11] pipe: Notification queue preparation " Linus Torvalds
2019-11-01 22:05 ` David Howells [this message]
2019-11-01 22:12 ` Linus Torvalds
2019-11-05 16:02 ` Details on the UAPI of implementing notifications on pipes David Howells
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