linux-kernel - Re: Memory providers multiplexing (Was: [PATCH net-next v4 4/5] page_pool: remove PP_FLAG_PAGE

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Date:   Sun, 2 Jul 2023 22:20:11 -0600
From:   David Ahern <dsahern@...nel.org>
To:     Mina Almasry <almasrymina@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Jesper Dangaard Brouer <jbrouer@...hat.com>, brouer@...hat.com,
        Alexander Duyck <alexander.duyck@...il.com>,
        Yunsheng Lin <linyunsheng@...wei.com>, davem@...emloft.net,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Sunil Goutham <sgoutham@...vell.com>,
        Geetha sowjanya <gakula@...vell.com>,
        Subbaraya Sundeep <sbhatta@...vell.com>,
        hariprasad <hkelam@...vell.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        Felix Fietkau <nbd@....name>,
        Ryder Lee <ryder.lee@...iatek.com>,
        Shayne Chen <shayne.chen@...iatek.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Kalle Valo <kvalo@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        linux-rdma@...r.kernel.org, linux-wireless@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Jonathan Lemon <jonathan.lemon@...il.com>
Subject: Re: Memory providers multiplexing (Was: [PATCH net-next v4 4/5]
 page_pool: remove PP_FLAG_PAGE_FRAG flag)

On 6/29/23 8:27 PM, Mina Almasry wrote:
> 
> Hello Jakub, I'm looking into device memory (peer-to-peer) networking
> actually, and I plan to pursue using the page pool as a front end.
> 
> Quick description of what I have so far:
> current implementation uses device memory with struct pages; I am
> putting all those pages in a gen_pool, and we have written an
> allocator that allocates pages from the gen_pool. In the driver, we
> use this allocator instead of alloc_page() (the driver in question is
> gve which currently doesn't use the page pool). When the driver is
> done with the p2p page, it simply decrements the refcount on it and
> the page is freed back to the gen_pool.

I take it these are typical Linux networking applications using standard
socket APIs (not dpdk or xdp sockets or such)? If so, what does tcpdump
show for those skbs with pages for the device memory?