From f6ec83265587b33eb44782f40d29f822992cc38a Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 8 Jan 2020 11:04:00 -0700 Subject: [PATCH] io_uring: enable option to only trigger eventfd for async completions to #26323588 commit f2842ab5b72d7ee5f7f8385c2d4f32c133f5837b upstream. 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 Signed-off-by: Jens Axboe Signed-off-by: Joseph Qi Acked-by: Xiaoguang Wang --- fs/io_uring.c | 17 ++++++++++++++++- include/uapi/linux/io_uring.h | 1 + 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 3544fe839f2d..d8f0fbeab6f3 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -206,6 +206,7 @@ struct io_ring_ctx { int account_mem: 1; int cq_overflow_flushed: 1; int drain_next: 1; + int eventfd_async: 1; /* * Ring buffer of indices into array of io_uring_sqe, which is @@ -963,13 +964,20 @@ static struct io_uring_cqe *io_get_cqring(struct io_ring_ctx *ctx) return &rings->cqes[tail & ctx->cq_mask]; } +static inline bool io_should_trigger_evfd(struct io_ring_ctx *ctx) +{ + if (!ctx->eventfd_async) + return true; + return io_wq_current_is_worker() || in_interrupt(); +} + static void io_cqring_ev_posted(struct io_ring_ctx *ctx) { if (waitqueue_active(&ctx->wait)) wake_up(&ctx->wait); if (waitqueue_active(&ctx->sqo_wait)) wake_up(&ctx->sqo_wait); - if (ctx->cq_ev_fd) + if (ctx->cq_ev_fd && io_should_trigger_evfd(ctx)) eventfd_signal(ctx->cq_ev_fd, 1); } @@ -6541,10 +6549,17 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode, ret = io_sqe_files_update(ctx, arg, nr_args); break; case IORING_REGISTER_EVENTFD: + case IORING_REGISTER_EVENTFD_ASYNC: ret = -EINVAL; if (nr_args != 1) break; ret = io_eventfd_register(ctx, arg); + if (ret) + break; + if (opcode == IORING_REGISTER_EVENTFD_ASYNC) + ctx->eventfd_async = 1; + else + ctx->eventfd_async = 0; break; case IORING_UNREGISTER_EVENTFD: ret = -EINVAL; diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index 0fe270ab191c..66772a90a7f2 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -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; -- GitLab