On 14/07/2023 14.51, Haiyang Zhang wrote:

quoted

-----Original Message-----
From: Jesper Dangaard Brouer <redacted>
On 14/07/2023 05.53, Jakub Kicinski wrote:

quoted

On Thu, 13 Jul 2023 14:48:45 +0000 Haiyang Zhang wrote:

quoted

Add page pool for RX buffers for faster buffer cycle and reduce CPU
usage.

Get an extra ref count of a page after allocation, so after upper
layers put the page, it's still referenced by the pool. We can reuse
it as RX buffer without alloc a new page.

Please use the real page_pool API from include/net/page_pool.h
We've moved past every driver reinventing the wheel, sorry.

+1

Quoting[1]: Documentation/networking/page_pool.rst

   Basic use involves replacing alloc_pages() calls with the
page_pool_alloc_pages() call.
   Drivers should use page_pool_dev_alloc_pages() replacing
dev_alloc_pages().

  
Thank Jakub and Jesper for the reviews.
I'm aware of the page_pool.rst doc, and actually tried it before this
patch, but I got lower perf. If I understand correctly, we should call
page_pool_release_page() before passing the SKB to napi_gro_receive().

I found the page_pool_dev_alloc_pages() goes through the slow path,
because the page_pool_release_page() let the page leave the pool.

Do we have to call page_pool_release_page() before passing the SKB
to napi_gro_receive()? Any better way to recycle the pages from the
upper layer of non-XDP case?

Today SKB "upper layers" can recycle page_pool backed packet data/page.

Just use skb_mark_for_recycle(skb), then you don't need 
page_pool_release_page().

I guess, we should update the documentation, mentioning this.

--Jesper