io_uring: use TWA_SIGNAL_NO_IPI if IORING_SETUP_COOP_TASKRUN is used
If this is set, io_uring will never use an IPI to deliver a task_work
notification. This can be used in the common case where a single task or
thread communicates with the ring, and doesn't rely on
io_uring_cqe_peek().
This provides a noticeable win in performance, both from eliminating
the IPI itself, but also from avoiding interrupting the submitting
task unnecessarily.
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/20220426014904.60384-6-axboe@kernel.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3c669d8..0b9ae36 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -11327,12 +11327,20 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
ctx->user = get_uid(current_user());
/*
- * For SQPOLL, we just need a wakeup, always.
+ * For SQPOLL, we just need a wakeup, always. For !SQPOLL, if
+ * COOP_TASKRUN is set, then IPIs are never needed by the app.
*/
- if (ctx->flags & IORING_SETUP_SQPOLL)
+ ret = -EINVAL;
+ if (ctx->flags & IORING_SETUP_SQPOLL) {
+ /* IPI related flags don't make sense with SQPOLL */
+ if (ctx->flags & IORING_SETUP_COOP_TASKRUN)
+ goto err;
ctx->notify_method = TWA_SIGNAL_NO_IPI;
- else
+ } else if (ctx->flags & IORING_SETUP_COOP_TASKRUN) {
+ ctx->notify_method = TWA_SIGNAL_NO_IPI;
+ } else {
ctx->notify_method = TWA_SIGNAL;
+ }
/*
* This is just grabbed for accounting purposes. When a process exits,
@@ -11431,7 +11439,8 @@ static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
if (p.flags & ~(IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL |
IORING_SETUP_SQ_AFF | IORING_SETUP_CQSIZE |
IORING_SETUP_CLAMP | IORING_SETUP_ATTACH_WQ |
- IORING_SETUP_R_DISABLED | IORING_SETUP_SUBMIT_ALL))
+ IORING_SETUP_R_DISABLED | IORING_SETUP_SUBMIT_ALL |
+ IORING_SETUP_COOP_TASKRUN))
return -EINVAL;
return io_uring_create(entries, &p, params);
