netdev - Re: [RFC net-next 01/13] net: page_pool: split the page_pool

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Date: Thu, 17 Aug 2023 14:28:53 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, hawk@...nel.org, ilias.apalodimas@...aro.org, 
	aleksander.lobakin@...el.com, linyunsheng@...wei.com
Subject: Re: [RFC net-next 01/13] net: page_pool: split the page_pool_params
 into fast and slow

On Wed, Aug 16, 2023 at 4:43 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> struct page_pool is rather performance critical and we use
> 16B of the first cache line to store 2 pointers used only
> by test code. Future patches will add more informational
> (non-fast path) attributes.
>
> It's convenient for the user of the API to not have to worry
> which fields are fast and which are slow path. Use struct
> groups to split the params into the two categories internally.
>
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>

Reviewed-by: Mina Almasry <almasrymina@...gle.com>

> ---
>  include/net/page_pool/types.h | 31 +++++++++++++++++++------------
>  net/core/page_pool.c          |  7 ++++---
>  2 files changed, 23 insertions(+), 15 deletions(-)
>
> diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
> index 887e7946a597..1c16b95de62f 100644
> --- a/include/net/page_pool/types.h
> +++ b/include/net/page_pool/types.h
> @@ -56,18 +56,22 @@ struct pp_alloc_cache {
>   * @offset:    DMA sync address offset for PP_FLAG_DMA_SYNC_DEV
>   */
>  struct page_pool_params {
> -       unsigned int    flags;
> -       unsigned int    order;
> -       unsigned int    pool_size;
> -       int             nid;
> -       struct device   *dev;
> -       struct napi_struct *napi;
> -       enum dma_data_direction dma_dir;
> -       unsigned int    max_len;
> -       unsigned int    offset;
> +       struct_group_tagged(page_pool_params_fast, fast,
> +               unsigned int    flags;
> +               unsigned int    order;
> +               unsigned int    pool_size;
> +               int             nid;
> +               struct device   *dev;
> +               struct napi_struct *napi;
> +               enum dma_data_direction dma_dir;
> +               unsigned int    max_len;
> +               unsigned int    offset;
> +       );
> +       struct_group_tagged(page_pool_params_slow, slow,
>  /* private: used by test code only */
> -       void (*init_callback)(struct page *page, void *arg);
> -       void *init_arg;
> +               void (*init_callback)(struct page *page, void *arg);
> +               void *init_arg;
> +       );
>  };
>
>  #ifdef CONFIG_PAGE_POOL_STATS
> @@ -121,7 +125,7 @@ struct page_pool_stats {
>  #endif
>
>  struct page_pool {
> -       struct page_pool_params p;
> +       struct page_pool_params_fast p;
>
>         long frag_users;
>         struct page *frag_page;
> @@ -180,6 +184,9 @@ struct page_pool {
>         refcount_t user_cnt;
>
>         u64 destroy_cnt;
> +
> +       /* Slow/Control-path information follows */
> +       struct page_pool_params_slow slow;
>  };
>
>  struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp);
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index 77cb75e63aca..ffe7782d7fc0 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -173,7 +173,8 @@ static int page_pool_init(struct page_pool *pool,
>  {
>         unsigned int ring_qsize = 1024; /* Default */
>
> -       memcpy(&pool->p, params, sizeof(pool->p));
> +       memcpy(&pool->p, &params->fast, sizeof(pool->p));
> +       memcpy(&pool->slow, &params->slow, sizeof(pool->slow));
>
>         /* Validate only known flags were used */
>         if (pool->p.flags & ~(PP_FLAG_ALL))
> @@ -372,8 +373,8 @@ static void page_pool_set_pp_info(struct page_pool *pool,
>  {
>         page->pp = pool;
>         page->pp_magic |= PP_SIGNATURE;
> -       if (pool->p.init_callback)
> -               pool->p.init_callback(page, pool->p.init_arg);
> +       if (pool->slow.init_callback)
> +               pool->slow.init_callback(page, pool->slow.init_arg);
>  }
>
>  static void page_pool_clear_pp_info(struct page *page)
> --
> 2.41.0
>


-- 
Thanks,
Mina