On 2021/7/2 17:42, Jesper Dangaard Brouer wrote: > > On 30/06/2021 11.17, Yunsheng Lin wrote: >> Currently page pool only support page recycling only when >> refcnt of page is one, which means it can not support the >> split page recycling implemented in the most ethernet driver. > > Cc. Alex Duyck as I consider him an expert in this area. Thanks. > > >> So add elevated refcnt support in page pool, and support >> allocating page frag to enable multi-frames-per-page based >> on the elevated refcnt support. >> >> As the elevated refcnt is per page, and there is no space >> for that in "struct page" now, so add a dynamically allocated >> "struct page_pool_info" to record page pool ptr and refcnt >> corrsponding to a page for now. Later, we can recycle the >> "struct page_pool_info" too, or use part of page memory to >> record pp_info. > > I'm not happy with allocating a memory (slab) object "struct page_pool_info" per page. > > This also gives us an extra level of indirection. I'm not happy with that either, if there is better way to avoid that, I will be happy to change it:) > > > You are also adding a page "frag" API inside page pool, which I'm not 100% convinced belongs inside page_pool APIs. > > Please notice the APIs that Alex Duyck added in mm/page_alloc.c: Actually, that is where the idea of using "page frag" come from. Aside from the performance improvement, there is memory usage decrease for 64K page size kernel, which means a 64K page can be used by 32 description with 2k buffer size, and that is a lot of memory saving for 64 page size kernel comparing to the current split page reusing implemented in the driver. > > __page_frag_cache_refill() + __page_frag_cache_drain() + page_frag_alloc_align() > > [...]
