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io_uring: enable option to only trigger eventfd for async completions

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If an application is using eventfd notifications with poll to know when
new SQEs can be issued, it's expecting the following read/writes to
complete inline. And with that, it knows that there are events available,
and don't want spurious wakeups on the eventfd for those requests.

This adds IORING_REGISTER_EVENTFD_ASYNC, which works just like
IORING_REGISTER_EVENTFD, except it only triggers notifications for events
that happen from async completions (IRQ, or io-wq worker completions).
Any completions inline from the submission itself will not trigger
notifications.

Suggested-by: Mark Papadakis <markuspapadakis@icloud.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2020-01-08 11:04:00 -07:00
parent 69b3e54613
commit f2842ab5b7
2 changed files with 17 additions and 1 deletions
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1
include/uapi/linux/io_uring.h
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@ -192,6 +192,7 @@ struct io_uring_params {
#define IORING_REGISTER_EVENTFD 4
#define IORING_UNREGISTER_EVENTFD 5
#define IORING_REGISTER_FILES_UPDATE 6
#define IORING_REGISTER_EVENTFD_ASYNC 7
struct io_uring_files_update {
__u32 offset;