Subject: Re: [PATCH net-next v4 5/5] page_pool: update document about frag API

From: Jakub Kicinski <[email-masked]>
Date: Tue, 13 Jun 2023 21:40:41 -0700

On Mon, 12 Jun 2023 21:02:56 +0800 Yunsheng Lin wrote:
> +2. page_pool_alloc_frag(): allocate memory with page splitting when driver knows
> +   that the memory it need is always smaller than or equal to half of the page
> +   allocated from page pool. Page splitting enables memory saving and thus avoid
> +   TLB/cache miss for data access, but there also is some cost to implement page
> +   splitting, mainly some cache line dirtying/bouncing for 'struct page' and
> +   atomic operation for page->pp_frag_count.
> +
> +3. page_pool_alloc(): allocate memory with or without page splitting depending
> +   on the requested memory size when driver doesn't know the size of memory it
> +   need beforehand. It is a mix of the above two case, so it is a wrapper of the
> +   above API to simplify driver's interface for memory allocation with least
> +   memory utilization and performance penalty.

Seems like the semantics of page_pool_alloc() are always better than
page_pool_alloc_frag(). Is there a reason to keep these two separate?