Re: [PATCH 2/2] io_uring: get rid of alloc cache init_once handling

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

On 1/23/25 14:21, Jens Axboe wrote:
> init_once is called when an object doesn't come from the cache, and
> hence needs initial clearing of certain members. While the whole
> struct could get cleared by memset() in that case, a few of the cache
> members are large enough that this may cause unnecessary overhead if
> the caches used aren't large enough to satisfy the workload. For those
> cases, some churn of kmalloc+kfree is to be expected.
> 
> Ensure that the 3 users that need clearing put the members they need
> cleared at the start of the struct, and place an empty placeholder
> 'init' member so that the cache initialization knows how much to
> clear.
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>   include/linux/io_uring/cmd.h   |  3 ++-
>   include/linux/io_uring_types.h |  3 ++-
>   io_uring/alloc_cache.h         | 30 +++++++++++++++++++++---------
>   io_uring/futex.c               |  4 ++--
>   io_uring/io_uring.c            | 13 ++++++++-----
>   io_uring/io_uring.h            |  5 ++---
>   io_uring/net.c                 | 11 +----------
>   io_uring/net.h                 |  7 +++++--
>   io_uring/poll.c                |  2 +-
>   io_uring/rw.c                  | 10 +---------
>   io_uring/rw.h                  |  5 ++++-
>   io_uring/uring_cmd.c           | 10 +---------
>   12 files changed, 50 insertions(+), 53 deletions(-)
> 
> diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
> index a3ce553413de..8d7746d9fd23 100644
> --- a/include/linux/io_uring/cmd.h
> +++ b/include/linux/io_uring/cmd.h
> @@ -19,8 +19,9 @@ struct io_uring_cmd {
>   };
>   
>   struct io_uring_cmd_data {
> -	struct io_uring_sqe	sqes[2];
>   	void			*op_data;
> +	int			init[0];

What do you think about using struct_group instead?

-- 
Pavel Begunkov