Re: [PATCH v1 1/2] io-wq: add exit-on-idle mode

[Jens Axboe <axboe@kernel.dk>]

On 2/2/26 7:37 AM, Li Chen wrote:
> io-wq uses an idle timeout to shrink the pool, but keeps the last worker
> around indefinitely to avoid churn.
> 
> For tasks that used io_uring for file I/O and then stop using io_uring,
> this can leave an iou-wrk-* thread behind even after all io_uring instances
> are gone. This is unnecessary overhead and also gets in the way of process
> checkpoint/restore.
> 
> Add an exit-on-idle mode that makes all io-wq workers exit as soon as they
> become idle, and provide io_wq_set_exit_on_idle() to toggle it.

Was going to say, rather than add a mode for this, why not just have the
idle single worker exit when the last ring is closed? But that is indeed
exactly what these two patches do. So I think this is fine, I just don't
think using the word "mode" for it is correct. "state" would be a lot
better - if we have all rings exited, then that's a state change in
terms of yeah let's just dump that idle worker.

With that in mind, I think these two patches look fine. I'll give them a
closer look. Could you perhaps write a test case for this?

-- 
Jens Axboe