netdev - Re: [PATCH net-next] page_pool: Rename frag_users to frag

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Date: Fri, 15 Dec 2023 19:09:58 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Ilias Apalodimas <ilias.apalodimas@...aro.org>, <netdev@...r.kernel.org>
CC: Jesper Dangaard Brouer <hawk@...nel.org>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] page_pool: Rename frag_users to frag_cnt

On 2023/12/15 15:31, Ilias Apalodimas wrote:
> Since [0] got merged, it's clear that 'pp_ref_count' is used to track
> the number of users for each page. On struct_page though we have
> a member called 'frag_users'. Despite of what the name suggests this is
> not the number of users. It instead represents the number of fragments of
> the current page. When we have a single page this is set to one. When we
> split the page this is set to the actual number of frags and later used
> in page_pool_drain_frag() to infer the real number of users.
> 
> So let's rename it to something that matches the description above
> 
> [0]
> Link: https://lore.kernel.org/netdev/20231212044614.42733-2-liangchen.linux@gmail.com/
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> ---
>  include/net/page_pool.h | 2 +-
>  net/core/page_pool.c    | 8 ++++----
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/include/net/page_pool.h b/include/net/page_pool.h
> index 813c93499f20..957cd84bb3f4 100644
> --- a/include/net/page_pool.h
> +++ b/include/net/page_pool.h
> @@ -158,7 +158,7 @@ struct page_pool {
>  	u32 pages_state_hold_cnt;
>  	unsigned int frag_offset;
>  	struct page *frag_page;
> -	long frag_users;
> +	long frag_cnt;

I would rename it to something like refcnt_bais to mirror the pagecnt_bias
in struct page_frag_cache.

> 
>  #ifdef CONFIG_PAGE_POOL_STATS
>  	/* these stats are incremented while in softirq context */
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index 9b203d8660e4..19a56a52ac8f 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -659,7 +659,7 @@ EXPORT_SYMBOL(page_pool_put_page_bulk);
>  static struct page *page_pool_drain_frag(struct page_pool *pool,
>  					 struct page *page)
>  {
> -	long drain_count = BIAS_MAX - pool->frag_users;
> +	long drain_count = BIAS_MAX - pool->frag_cnt;

drain_count = pool->refcnt_bais;

or

remove it and use pool->refcnt_bais directly.

> 
>  	/* Some user is still using the page frag */
>  	if (likely(page_pool_defrag_page(page, drain_count)))
> @@ -678,7 +678,7 @@ static struct page *page_pool_drain_frag(struct page_pool *pool,
> 
>  static void page_pool_free_frag(struct page_pool *pool)
>  {
> -	long drain_count = BIAS_MAX - pool->frag_users;
> +	long drain_count = BIAS_MAX - pool->frag_cnt;

Same here.

>  	struct page *page = pool->frag_page;
> 
>  	pool->frag_page = NULL;
> @@ -721,14 +721,14 @@ struct page *page_pool_alloc_frag(struct page_pool *pool,
>  		pool->frag_page = page;
> 
>  frag_reset:
> -		pool->frag_users = 1;
> +		pool->frag_cnt = 1;

pool->refcnt_bais = BIAS_MAX - 1;

>  		*offset = 0;
>  		pool->frag_offset = size;
>  		page_pool_fragment_page(page, BIAS_MAX);
>  		return page;
>  	}
> 
> -	pool->frag_users++;
> +	pool->frag_cnt++;

pool->refcnt_bais--;

>  	pool->frag_offset = *offset + size;
>  	alloc_stat_inc(pool, fast);
>  	return page;
> --
> 2.37.2
> 
> .
>