Re: [PATCH net-next 2/3] net: stmmac: Use pagepool instead of streaming buffers for Tx

On Mon, Aug 3, 2026 at 12:08 AM
<muhammad.nazim.amirul.nazle.asmade-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org> wrote:
>
> From: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org>
>
> Use page pool buffers instead of streaming skb buffers in stmmac_xmit
> when snps,pagepool-tx-buf-quirk is enabled. As page pool buffers are
> recycled, the overhead of dma map/unmap for each transmit can be
> avoided. There is a trade-off of copying from the skb into the page
> pool buffer, but this helps where the copy is cheaper than dma
> map/unmap (for example with IOMMU invalidate cost).
>
> Currently page pool buffers are only used for single-fragment transmit
> in the non-TSO path.
>
> Signed-off-by: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade-EIB2kfCEcldhl2p70BpVqQ@public.gmane.orgm>

Whoa!

I haven't looked at the patch deeply to be honest, but using the
page-pool for tx is a bit interesting. There is no other code that
uses it like that I think. I can't think of any blockers off the top
of my head, but I think there are places where we keep a global list
of created page_pools on the system/netdev and the code parses those
lists may be assuming it's a normal page-pool, which is a pp used for
rx and attached to the an rx queue.

Just Ccing the maintainers of pp to know about this use case. I can't
think of issues again, but I wonder if a more-expert has thoughts.

-- 
Thanks,
Mina