Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> 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)) {
