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

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Message-ID: <20230711090047.37d7fe06@kernel.org>
Date:   Tue, 11 Jul 2023 09:00:47 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Jason Gunthorpe <jgg@...pe.ca>, Christoph Hellwig <hch@....de>
Cc:     Mina Almasry <almasrymina@...gle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Ahern <dsahern@...nel.org>,
        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 Tue, 11 Jul 2023 09:05:02 -0300 Jason Gunthorpe wrote:
> On Tue, Jul 11, 2023 at 07:04:45AM +0200, Christoph Hellwig wrote:
> > On Mon, Jul 10, 2023 at 09:59:06PM -0700, Jakub Kicinski wrote:  
> > > Noob question - how does RDMA integrate with the out of tree junk?
> > > AFAIU it's possible to run the "in-tree" RDMA stack and get "GPU
> > > direct".  
> > 
> > I don't care and it has absolutel no business being discussed here.

My question was genuine. If you think the code is dog shit I will 
make no argument for merging it. I just get hives from looking at
proprietary code so I was hoping someone could explain how the
proprietary stacks get it done.

> > FYI at leat iWarp is a totally open standard.  

And I'm sure someone cares about that. I care about open source.

I think people in the networking world have a deeper understanding 
of standardization processes, and their practical implication for
open source and hack-ability. If all usable implementations are
proprietary the standard could as well not exist.

That may be a little hard to understand for folks coming from storage
and fabric worlds where the interesting bits of the implementation was
pretty much always closed.

> So is Infiniband, Jakub has a unique definition of "proprietary".

For IB AFAIU there's only one practically usable vendor, such an
impressive ecosystem!!

> RDMA works with the AMD and Intel intree drivers using DMABUF without
> requiring struct pages using the DRM hacky scatterlist approach.

I see, thanks. We need pages primarily for refcounting. Avoiding all
the infamous problems with memory pins. Oh well.