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io_uring/napi: cap busy_poll_to 10 msec

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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: 8d0c12a80c ("io-uring: add napi busy poll support")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2026-04-27 14:42:18 -06:00
parent 7deba791ad
commit df8599ee18
1 changed files with 2 additions and 0 deletions
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io_uring/napi.c
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@ -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;