From: Christoph Hellwig <hch@lst.de>
To: viro@zeniv.linux.org.uk
Cc: Avi Kivity <avi@scylladb.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 4/4 v2] aio: allow direct aio poll comletions for keyed wakeups
Date: Tue, 7 Aug 2018 13:44:51 +0200 [thread overview]
Message-ID: <20180807114451.GA8853@lst.de> (raw)
In-Reply-To: <20180806083058.14724-5-hch@lst.de>
If we get a keyed wakeup for a aio poll waitqueue and wake can acquire the
ctx_lock without spinning we can just complete the iocb straight from the
wakeup callback to avoid a context switch.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Avi Kivity <avi@scylladb.com>
---
Fix a subject line typo and improve a comment.
fs/aio.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index 2fd19521d8a8..5943098a87c6 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1672,13 +1672,29 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
void *key)
{
struct poll_iocb *req = container_of(wait, struct poll_iocb, wait);
+ struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll);
__poll_t mask = key_to_poll(key);
req->woken = true;
/* for instances that support it check for an event match first: */
- if (mask && !(mask & req->events))
- return 0;
+ if (mask) {
+ if (!(mask & req->events))
+ return 0;
+
+ /*
+ * Try to complete the iocb inline if we can to avoid a costly
+ * context switch.
+ */
+ if (spin_trylock(&iocb->ki_ctx->ctx_lock)) {
+ list_del(&iocb->ki_list);
+ spin_unlock(&iocb->ki_ctx->ctx_lock);
+
+ list_del_init(&req->wait.entry);
+ aio_poll_complete(iocb, mask);
+ return 1;
+ }
+ }
list_del_init(&req->wait.entry);
schedule_work(&req->work);
--
2.18.0
next prev parent reply other threads:[~2018-08-07 11:39 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-06 8:30 aio poll V22 (aka 2.0) Christoph Hellwig
2018-08-06 8:30 ` [PATCH 1/4] timerfd: add support for keyed wakeups Christoph Hellwig
2018-08-06 8:30 ` [PATCH 2/4] aio: add a iocb refcount Christoph Hellwig
2018-08-06 8:30 ` [PATCH 3/4] aio: implement IOCB_CMD_POLL Christoph Hellwig
2018-08-06 8:30 ` [PATCH 4/4] aio: allow direct aio poll comletions for keyed wakeups Christoph Hellwig
2018-08-06 22:27 ` Andrew Morton
2018-08-07 7:25 ` Christoph Hellwig
2018-08-07 16:04 ` Andrew Morton
2018-08-08 9:57 ` Christoph Hellwig
2018-08-07 11:44 ` Christoph Hellwig [this message]
2018-08-06 16:49 ` aio poll V22 (aka 2.0) Linus Torvalds
2018-08-07 7:27 ` Christoph Hellwig
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