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io_uring: enable EPOLLEXCLUSIVE for accept poll

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When polling sockets for accept, use EPOLLEXCLUSIVE. This is helpful
when multiple accept SQEs are submitted.

For O_NONBLOCK sockets multiple queued SQEs would previously have all
completed at once, but most with -EAGAIN as the result. Now only one
wakes up and completes.

For sockets without O_NONBLOCK there is no user facing change, but
internally the extra requests would previously be queued onto a worker
thread as they would wake up with no connection waiting, and be
punted. Now they do not wake up unnecessarily.

Co-developed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220325093755.4123343-1-dylany@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Dylan Yudaken 2022-03-25 02:37:55 -07:00 committed by Jens Axboe
parent 34d2bfe7d4
commit 52dd86406d
1 changed files with 4 additions and 1 deletions
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5
fs/io_uring.c
View file

@ -967,6 +967,7 @@ struct io_op_def {
/* set if opcode supports polled "wait" */
unsigned pollin : 1;
unsigned pollout : 1;
unsigned poll_exclusive : 1;
/* op supports buffer selection */
unsigned buffer_select : 1;
/* do prep async if is going to be punted */
@ -1061,6 +1062,7 @@ static const struct io_op_def io_op_defs[] = {
.needs_file = 1,
.unbound_nonreg_file = 1,
.pollin = 1,
.poll_exclusive = 1,
},
[IORING_OP_ASYNC_CANCEL] = {
.audit_skip = 1,
@ -6280,7 +6282,8 @@ static int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags)
} else {
mask |= POLLOUT | POLLWRNORM;
}
if (def->poll_exclusive)
mask |= EPOLLEXCLUSIVE;
if (!(issue_flags & IO_URING_F_UNLOCKED) &&
!list_empty(&ctx->apoll_cache)) {
apoll = list_first_entry(&ctx->apoll_cache, struct async_poll,