Re: [PATCHv5 11/11] io_uring: cache nodes and mapped buffers

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

On 2/24/25 21:31, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> Frequent alloc/free cycles on these is pretty costly. Use an io cache to
> more efficiently reuse these buffers.
> 
> Signed-off-by: Keith Busch <kbusch@kernel.org>
> ---
>   include/linux/io_uring_types.h |  18 ++---
>   io_uring/filetable.c           |   2 +-
>   io_uring/rsrc.c                | 120 +++++++++++++++++++++++++--------
>   io_uring/rsrc.h                |   2 +-
>   4 files changed, 104 insertions(+), 38 deletions(-)
> 
...
> +static __cold int io_rsrc_buffer_alloc(struct io_buf_table *table, unsigned nr)
> +{
> +	const int imu_cache_size = struct_size_t(struct io_mapped_ubuf, bvec,
> +						 IO_CACHED_BVECS_SEGS);
> +	const int node_size = sizeof(struct io_rsrc_node);
> +	int ret;
> +
> +	ret = io_rsrc_data_alloc(&table->data, nr);
> +	if (ret)
> +		return ret;
> +
> +	if (io_alloc_cache_init(&table->node_cache, nr, node_size, 0))

We shouldn't use nr for the cache size, that could be unreasonably
huge for a cache. Let's use a constant for now and that should be
good enough, at least for now. 64 would be a good default. Same for
the imu cache.

-- 
Pavel Begunkov