By default, io_uring marks a waiting task as being in iowait, if it's sleeping waiting on events and there are pending requests. This isn't necessarily always useful, and may be confusing on non-storage setups where iowait isn't expected. It can also cause extra power usage, by preventing the CPU from entering lower sleep states. This adds a new enter flag, IORING_ENTER_NO_IOWAIT. If set, then io_uring will not mark the sleeping task as being in iowait. If the kernel support this feature, then it will be marked by having the IORING_FEAT_NO_IOWAIT feature flag set. Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> --- Basic liburing support and a test case here: https://git.kernel.dk/cgit/liburing/log/?h=iowait Since v1: - Add IORING_ENTER_NO_IOWAIT feature flag diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index 050fa8eb2e8f..0d6c83c8d1cf 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -541,6 +541,7 @@ struct io_cqring_offsets { #define IORING_ENTER_REGISTERED_RING (1U << 4) #define IORING_ENTER_ABS_TIMER (1U << 5) #define IORING_ENTER_EXT_ARG_REG (1U << 6) +#define IORING_ENTER_NO_IOWAIT (1U << 7) /* * Passed in for io_uring_setup(2). Copied back with updated info on success @@ -578,6 +579,7 @@ struct io_uring_params { #define IORING_FEAT_RECVSEND_BUNDLE (1U << 14) #define IORING_FEAT_MIN_TIMEOUT (1U << 15) #define IORING_FEAT_RW_ATTR (1U << 16) +#define IORING_FEAT_NO_IOWAIT (1U << 17) /* * io_uring_register(2) opcodes and arguments diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 58003fa6b327..d975e68e91f2 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2485,8 +2485,18 @@ static int io_cqring_schedule_timeout(struct io_wait_queue *iowq, return READ_ONCE(iowq->hit_timeout) ? -ETIME : 0; } +struct ext_arg { + size_t argsz; + struct timespec64 ts; + const sigset_t __user *sig; + ktime_t min_time; + bool ts_set; + bool iowait; +}; + static int __io_cqring_wait_schedule(struct io_ring_ctx *ctx, struct io_wait_queue *iowq, + struct ext_arg *ext_arg, ktime_t start_time) { int ret = 0; @@ -2496,7 +2506,7 @@ static 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 (ext_arg->iowait && current_pending_io()) current->in_iowait = 1; if (iowq->timeout != KTIME_MAX || iowq->min_timeout) ret = io_cqring_schedule_timeout(iowq, ctx->clockid, start_time); @@ -2509,6 +2519,7 @@ static int __io_cqring_wait_schedule(struct io_ring_ctx *ctx, /* If this returns > 0, the caller should retry */ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx, struct io_wait_queue *iowq, + struct ext_arg *ext_arg, ktime_t start_time) { if (unlikely(READ_ONCE(ctx->check_cq))) @@ -2522,17 +2533,9 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx, if (unlikely(io_should_wake(iowq))) return 0; - return __io_cqring_wait_schedule(ctx, iowq, start_time); + return __io_cqring_wait_schedule(ctx, iowq, ext_arg, start_time); } -struct ext_arg { - size_t argsz; - struct timespec64 ts; - const sigset_t __user *sig; - ktime_t min_time; - bool ts_set; -}; - /* * Wait until events become available, if we don't already have some. The * application must reap them itself, as they reside on the shared cq ring. @@ -2610,7 +2613,7 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, u32 flags, TASK_INTERRUPTIBLE); } - ret = io_cqring_wait_schedule(ctx, &iowq, start_time); + ret = io_cqring_wait_schedule(ctx, &iowq, ext_arg, start_time); __set_current_state(TASK_RUNNING); atomic_set(&ctx->cq_wait_nr, IO_CQ_WAKE_INIT); @@ -3261,6 +3264,8 @@ static int io_get_ext_arg(struct io_ring_ctx *ctx, unsigned flags, const struct io_uring_getevents_arg __user *uarg = argp; struct io_uring_getevents_arg arg; + ext_arg->iowait = !(flags & IORING_ENTER_NO_IOWAIT); + /* * If EXT_ARG isn't set, then we have no timespec and the argp pointer * is just a pointer to the sigset_t. @@ -3338,7 +3343,8 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, IORING_ENTER_SQ_WAIT | IORING_ENTER_EXT_ARG | IORING_ENTER_REGISTERED_RING | IORING_ENTER_ABS_TIMER | - IORING_ENTER_EXT_ARG_REG))) + IORING_ENTER_EXT_ARG_REG | + IORING_ENTER_NO_IOWAIT))) return -EINVAL; /* @@ -3752,7 +3758,7 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p, IORING_FEAT_RSRC_TAGS | IORING_FEAT_CQE_SKIP | IORING_FEAT_LINKED_FILE | IORING_FEAT_REG_REG_RING | IORING_FEAT_RECVSEND_BUNDLE | IORING_FEAT_MIN_TIMEOUT | - IORING_FEAT_RW_ATTR; + IORING_FEAT_RW_ATTR | IORING_FEAT_NO_IOWAIT; if (copy_to_user(params, p, sizeof(*p))) { ret = -EFAULT; -- Jens Axboe
