netdev - 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.