Commit df8599ee authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring/napi: cap busy_poll_to 10 msec 



Currently there's no cap on the maximum amount of time that napi is
allowed to poll if no events are found, which can lead to kernel
complaints on a task being stuck as there's no conditional rescheduling
done within that loop.

Just cap it to 10 msec in total, that's already way above any kind of
sane value that will reap any benefits, yet low enough that it's
nowhere near being able to trigger preemption complaints.

Fixes: 8d0c12a8 ("io-uring: add napi busy poll support")
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 7deba791

io_uring/napi.c

+2 −0
Original line number Diff line number Diff line
@@ -276,6 +276,8 @@ static int io_napi_register_napi(struct io_ring_ctx *ctx, 
	/* clean the napi list for new settings */

	io_napi_free(ctx);

	WRITE_ONCE(ctx->napi_track_mode, napi->op_param);

	/* cap NAPI at 10 msec of spin time */

	napi->busy_poll_to = min(10000, napi->busy_poll_to);

	WRITE_ONCE(ctx->napi_busy_poll_dt, napi->busy_poll_to * NSEC_PER_USEC);

	WRITE_ONCE(ctx->napi_prefer_busy_poll, !!napi->prefer_busy_poll);

	return 0;