The current logic of requests with IOSQE_ASYNC is first queueing it to
io-worker, then execute it in a synchronous way. For unbound works like
pollable requests(e.g. read/write a socketfd), the io-worker may stuck
there waiting for events for a long time. And thus other works wait in
the list for a long time too.
Let's introduce a new way for unbound works (currently pollable
requests), with this a request will first be queued to io-worker, then
executed in a nonblock try rather than a synchronous way. Failure of
that leads it to arm poll stuff and then the worker can begin to handle
other works.
The detail process of this kind of requests is:
step1: original context:
queue it to io-worker
step2: io-worker context:
nonblock try(the old logic is a synchronous try here)
|
|--fail--> arm poll
|
|--(fail/ready)-->synchronous issue
|
|--(succeed)-->worker finish it's job, tw
take over the req
This works much better than the old IOSQE_ASYNC logic in cases where
unbound max_worker is relatively small. In this case, number of
io-worker eazily increments to max_worker, new worker cannot be created
and running workers stuck there handling old works in IOSQE_ASYNC mode.
In my 64-core machine, set unbound max_worker to 20, run echo-server,
turns out:
(arguments: register_file, connetion number is 1000, message size is 12
Byte)
original IOSQE_ASYNC: 76664.151 tps
after this patch: 166934.985 tps
Suggested-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>
---
v1-->v2:
- tweak added code in io_wq_submit_work to reduce overhead
v2-->v3:
- remove redundant IOSQE_ASYNC_HYBRID stuff
fs/io_uring.c | 36 +++++++++++++++++++++++++++++++++++-
1 file changed, 35 insertions(+), 1 deletion(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index b3546eef0289..86819c7917df 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6747,8 +6747,18 @@ static void io_wq_submit_work(struct io_wq_work *work)
ret = -ECANCELED;
if (!ret) {
+ bool needs_poll = false;
+ unsigned int issue_flags = IO_URING_F_UNLOCKED;
+
+ if (req->flags & REQ_F_FORCE_ASYNC) {
+ needs_poll = req->file && file_can_poll(req->file);
+ if (needs_poll)
+ issue_flags |= IO_URING_F_NONBLOCK;
+ }
+
do {
- ret = io_issue_sqe(req, IO_URING_F_UNLOCKED);
+issue_sqe:
+ ret = io_issue_sqe(req, issue_flags);
/*
* We can get EAGAIN for polled IO even though we're
* forcing a sync submission from here, since we can't
@@ -6756,6 +6766,30 @@ static void io_wq_submit_work(struct io_wq_work *work)
*/
if (ret != -EAGAIN)
break;
+ if (needs_poll) {
+ bool armed = false;
+
+ ret = 0;
+ needs_poll = false;
+ issue_flags &= ~IO_URING_F_NONBLOCK;
+
+ switch (io_arm_poll_handler(req)) {
+ case IO_APOLL_READY:
+ goto issue_sqe;
+ case IO_APOLL_ABORTED:
+ /*
+ * somehow we failed to arm the poll infra,
+ * fallback it to a normal async worker try.
+ */
+ break;
+ case IO_APOLL_OK:
+ armed = true;
+ break;
+ }
+
+ if (armed)
+ break;
+ }
cond_resched();
} while (1);
}
--
2.24.4
