ping
On 2021/11/22 12:11, yangerkun wrote:
Once enable CONFIG_WATCH_QUEUE, we should protect pipe with
pipe->rd_wait.lock since post_one_notification may write pipe from
contexts where pipe->mutex cannot be token. But nowdays we will try
take it for anycase, it seems needless. Besides, pipe_write will break
once it's pipe with O_NOTIFICATION_PIPE, pipe->rd_wait.lock seems no
need at all. We make some change base on that, and it can help improve
performance for some case like pipe_pst1 in libMicro.
ARMv7 for our scene, before this patch:
5483 nsecs/call
After this patch:
4854 nsecs/call
Signed-off-by: yangerkun <yangerkun@xxxxxxxxxx>
---
fs/pipe.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/fs/pipe.c b/fs/pipe.c
index 6d4342bad9f1..e8ced0c50824 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -320,14 +320,18 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
if (!buf->len) {
pipe_buf_release(pipe, buf);
- spin_lock_irq(&pipe->rd_wait.lock);
#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->watch_queue)
+ spin_lock_irq(&pipe->rd_wait.lock);
if (buf->flags & PIPE_BUF_FLAG_LOSS)
pipe->note_loss = true;
#endif
tail++;
pipe->tail = tail;
- spin_unlock_irq(&pipe->rd_wait.lock);
+#ifdef CONFIG_WATCH_QUEUE
+ if (pipe->watch_queue)
+ spin_unlock_irq(&pipe->rd_wait.lock);
+#endif
}
total_len -= chars;
if (!total_len)
@@ -504,16 +508,11 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
* it, either the reader will consume it or it'll still
* be there for the next write.
*/
- spin_lock_irq(&pipe->rd_wait.lock);
-
head = pipe->head;
- if (pipe_full(head, pipe->tail, pipe->max_usage)) {
- spin_unlock_irq(&pipe->rd_wait.lock);
+ if (pipe_full(head, pipe->tail, pipe->max_usage))
continue;
- }
pipe->head = head + 1;
- spin_unlock_irq(&pipe->rd_wait.lock);
/* Insert it into the buffer array */
buf = &pipe->bufs[head & mask];
