netdev - RE: [PATCH net-next] net: mana: Add page pool for RX buffers

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Date: Fri, 14 Jul 2023 12:51:41 +0000
From: Haiyang Zhang <haiyangz@...rosoft.com>
To: Jesper Dangaard Brouer <jbrouer@...hat.com>, Jakub Kicinski
	<kuba@...nel.org>
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	<bpf@...r.kernel.org>, "ast@...nel.org" <ast@...nel.org>, Ajay Sharma
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	<linux-kernel@...r.kernel.org>, Ilias Apalodimas
	<ilias.apalodimas@...aro.org>
Subject: RE: [PATCH net-next] net: mana: Add page pool for RX buffers



> -----Original Message-----
> From: Jesper Dangaard Brouer <jbrouer@...hat.com>
> On 14/07/2023 05.53, Jakub Kicinski wrote:
> > On Thu, 13 Jul 2023 14:48:45 +0000 Haiyang Zhang wrote:
> >> 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?

Thanks,
- Haiyang