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

[Haiyang Zhang]

> -----Original Message-----
> From: Jesper Dangaard Brouer <jbrouer@xxxxxxxxxx>
> Sent: Friday, July 14, 2023 9:13 AM
> To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; Jesper Dangaard Brouer
> <jbrouer@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>
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> Subject: Re: [PATCH net-next] net: mana: Add page pool for RX buffers
> 
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> 
> On 14/07/2023 14.51, Haiyang Zhang wrote:
> >
> >
> >> -----Original Message-----
> >> From: Jesper Dangaard Brouer <jbrouer@xxxxxxxxxx>
> >> 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?
> >
> 
> 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().

Will do. Thanks a lot!

- Haiyang