Re: [PATCH] io_uring: don't iterate ctx list to update sq_thread_idle

[Pavel Begunkov <asml.silence@gmail.com>]

On 15/03/2021 08:56, Hao Xu wrote:
> sqd->sq_thread_idle can be updated by a simple max(), rather than
> iterating the whole ctx list to get the max one.

I left it as a more fool proof option. Do you have a performance issue
with it? E.g. dozens rings sharing a single SQPOLL and constantly adding
new ones.

> 
> Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
> ---
>  fs/io_uring.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index a4bce17af506..17697b9890e3 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -7871,7 +7871,7 @@ static int io_sq_offload_create(struct io_ring_ctx *ctx,
>  			ret = -ENXIO;
>  		} else {
>  			list_add(&ctx->sqd_list, &sqd->ctx_list);
> -			io_sqd_update_thread_idle(sqd);
> +			sqd->sq_thread_idle = max(sqd->sq_thread_idle, ctx->sq_thread_idle);
>  		}
>  		io_sq_thread_unpark(sqd);
>  
> 

-- 
Pavel Begunkov