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| author | Jens Axboe <axboe@kernel.dk> | 2023-08-01 08:42:37 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-08-11 12:08:08 +0200 |
| commit | c7920f992840779383cbff15a2e860515eec7644 (patch) | |
| tree | 71eae4122666e2acdfc51053b2161e6bc54f1380 /io_uring | |
| parent | 0a4a7855302d56a1d75cec3aa9a6914a3af9c6af (diff) | |
| download | linux-stable-c7920f992840779383cbff15a2e860515eec7644.tar.gz linux-stable-c7920f992840779383cbff15a2e860515eec7644.tar.bz2 linux-stable-c7920f992840779383cbff15a2e860515eec7644.zip | |
io_uring: gate iowait schedule on having pending requests
Commit 7b72d661f1f2f950ab8c12de7e2bc48bdac8ed69 upstream.
A previous commit made all cqring waits marked as iowait, as a way to
improve performance for short schedules with pending IO. However, for
use cases that have a special reaper thread that does nothing but
wait on events on the ring, this causes a cosmetic issue where we
know have one core marked as being "busy" with 100% iowait.
While this isn't a grave issue, it is confusing to users. Rather than
always mark us as being in iowait, gate setting of current->in_iowait
to 1 by whether or not the waiting task has pending requests.
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/io-uring/CAMEGJJ2RxopfNQ7GNLhr7X9=bHXKo+G5OOe0LUq=+UgLXsv1Xg@mail.gmail.com/
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217699
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217700
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Reported-by: Phil Elwell <phil@raspberrypi.com>
Tested-by: Andres Freund <andres@anarazel.de>
Fixes: 8a796565cec3 ("io_uring: Use io_schedule* in cqring wait")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'io_uring')
| -rw-r--r-- | io_uring/io_uring.c | 23 |
1 files changed, 17 insertions, 6 deletions
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index f091153bc854..ed8e9deae284 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2349,12 +2349,21 @@ int io_run_task_work_sig(struct io_ring_ctx *ctx) return 0; } +static bool current_pending_io(void) +{ + struct io_uring_task *tctx = current->io_uring; + + if (!tctx) + return false; + return percpu_counter_read_positive(&tctx->inflight); +} + /* when returns >0, the caller should retry */ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx, struct io_wait_queue *iowq, ktime_t *timeout) { - int token, ret; + int io_wait, ret; unsigned long check_cq; /* make sure we run task_work before checking for signals */ @@ -2372,15 +2381,17 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx, } /* - * Use io_schedule_prepare/finish, so cpufreq can take into account - * that the task is waiting for IO - turns out to be important for low - * QD IO. + * Mark us as being in io_wait if we have pending requests, so cpufreq + * can take into account that the task is waiting for IO - turns out + * to be important for low QD IO. */ - token = io_schedule_prepare(); + io_wait = current->in_iowait; + if (current_pending_io()) + current->in_iowait = 1; ret = 1; if (!schedule_hrtimeout(timeout, HRTIMER_MODE_ABS)) ret = -ETIME; - io_schedule_finish(token); + current->in_iowait = io_wait; return ret; } |