It may be that certain (all?) network functions, like recv, should not
be accounted as iowait. However, I don't think the onus should be on
applications to tell the kernel about that--the kernel should just
figure that out on its own.
Am I alone in these opinions?
Cheers,
Jeff
>
> Signed-off-by: David Wei <dw@xxxxxxxxxxx>
> ---
> v2:
> - squash patches into one
> - move no_iowait in struct io_wait_queue to the end
> - always set iowq.no_iowait
>
> ---
> include/uapi/linux/io_uring.h | 2 ++
> io_uring/io_uring.c | 7 ++++---
> io_uring/io_uring.h | 1 +
> 3 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index 48c440edf674..3a94afa8665e 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -508,6 +508,7 @@ struct io_cqring_offsets {
> #define IORING_ENTER_EXT_ARG (1U << 3)
> #define IORING_ENTER_REGISTERED_RING (1U << 4)
> #define IORING_ENTER_ABS_TIMER (1U << 5)
> +#define IORING_ENTER_NO_IOWAIT (1U << 6)
>
> /*
> * Passed in for io_uring_setup(2). Copied back with updated info on success
> @@ -543,6 +544,7 @@ struct io_uring_params {
> #define IORING_FEAT_LINKED_FILE (1U << 12)
> #define IORING_FEAT_REG_REG_RING (1U << 13)
> #define IORING_FEAT_RECVSEND_BUNDLE (1U << 14)
> +#define IORING_FEAT_IOWAIT_TOGGLE (1U << 15)
>
> /*
> * io_uring_register(2) opcodes and arguments
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 20229e72b65c..5e75672525df 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -2372,7 +2372,7 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
> * can take into account that the task is waiting for IO - turns out
> * to be important for low QD IO.
> */
> - if (current_pending_io())
> + if (!iowq->no_iowait && current_pending_io())
> current->in_iowait = 1;
> ret = 0;
> if (iowq->timeout == KTIME_MAX)
> @@ -2414,6 +2414,7 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, u32 flags,
> iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts);
> iowq.cq_tail = READ_ONCE(ctx->rings->cq.head) + min_events;
> iowq.timeout = KTIME_MAX;
> + iowq.no_iowait = flags & IORING_ENTER_NO_IOWAIT;
>
> if (uts) {
> struct timespec64 ts;
> @@ -3155,7 +3156,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
> if (unlikely(flags & ~(IORING_ENTER_GETEVENTS | IORING_ENTER_SQ_WAKEUP |
> IORING_ENTER_SQ_WAIT | IORING_ENTER_EXT_ARG |
> IORING_ENTER_REGISTERED_RING |
> - IORING_ENTER_ABS_TIMER)))
> + IORING_ENTER_ABS_TIMER | IORING_ENTER_NO_IOWAIT)))
> return -EINVAL;
>
> /*
> @@ -3539,7 +3540,7 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
> IORING_FEAT_EXT_ARG | IORING_FEAT_NATIVE_WORKERS |
> IORING_FEAT_RSRC_TAGS | IORING_FEAT_CQE_SKIP |
> IORING_FEAT_LINKED_FILE | IORING_FEAT_REG_REG_RING |
> - IORING_FEAT_RECVSEND_BUNDLE;
> + IORING_FEAT_RECVSEND_BUNDLE | IORING_FEAT_IOWAIT_TOGGLE;
>
> if (copy_to_user(params, p, sizeof(*p))) {
> ret = -EFAULT;
> diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
> index 9935819f12b7..426079a966ac 100644
> --- a/io_uring/io_uring.h
> +++ b/io_uring/io_uring.h
> @@ -46,6 +46,7 @@ struct io_wait_queue {
> ktime_t napi_busy_poll_dt;
> bool napi_prefer_busy_poll;
> #endif
> + bool no_iowait;
> };
>
> static inline bool io_should_wake(struct io_wait_queue *iowq)
