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Message-ID: <a8df4459-30bf-4414-aeca-2f67c461adc4@gmail.com>
Date: Fri, 7 Jun 2024 16:46:57 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: David Ahern <dsahern@...nel.org>, Mina Almasry <almasrymina@...gle.com>
Cc: Christoph Hellwig <hch@...radead.org>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-alpha@...r.kernel.org, linux-mips@...r.kernel.org,
 linux-parisc@...r.kernel.org, sparclinux@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
 bpf@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Donald Hunter <donald.hunter@...il.com>, Jonathan Corbet <corbet@....net>,
 Richard Henderson <richard.henderson@...aro.org>,
 Ivan Kokshaysky <ink@...assic.park.msu.ru>, Matt Turner
 <mattst88@...il.com>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
 "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
 Helge Deller <deller@....de>, Andreas Larsson <andreas@...sler.com>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 Ilias Apalodimas <ilias.apalodimas@...aro.org>,
 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Arnd Bergmann <arnd@...db.de>, Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman
 <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Steffen Klassert
 <steffen.klassert@...unet.com>, Herbert Xu <herbert@...dor.apana.org.au>,
 Willem de Bruijn <willemdebruijn.kernel@...il.com>,
 Shuah Khan <shuah@...nel.org>, Sumit Semwal <sumit.semwal@...aro.org>,
 Christian König <christian.koenig@....com>,
 David Wei <dw@...idwei.uk>, Jason Gunthorpe <jgg@...pe.ca>,
 Yunsheng Lin <linyunsheng@...wei.com>, Shailend Chand <shailend@...gle.com>,
 Harshitha Ramamurthy <hramamurthy@...gle.com>,
 Shakeel Butt <shakeel.butt@...ux.dev>, Jeroen de Borst
 <jeroendb@...gle.com>, Praveen Kaligineedi <pkaligineedi@...gle.com>
Subject: Re: [PATCH net-next v10 02/14] net: page_pool: create hooks for
 custom page providers

On 6/7/24 16:42, Pavel Begunkov wrote:
> On 6/7/24 15:27, David Ahern wrote:
>> On 6/7/24 7:42 AM, Pavel Begunkov wrote:
>>> I haven't seen any arguments against from the (net) maintainers so
>>> far. Nor I see any objection against callbacks from them (considering
>>> that either option adds an if).
>>
>> I have said before I do not understand why the dmabuf paradigm is not
>> sufficient for both device memory and host memory. A less than ideal
>> control path to put hostmem in a dmabuf wrapper vs extra checks and
>> changes in the datapath. The former should always be preferred.
> 
> If we're talking about types of memory specifically, I'm not strictly
> against wrapping into dmabuf in kernel, but that just doesn't give
> anything.

And the reason I don't have too strong of an opinion on that is
mainly because it's just setup/cleanup path.

> But the main reason for allocations there is the difference in
> approaches to the api. With io_uring the allocation callback is
> responsible for getting buffers back from the user (via a shared
> ring). No locking for the ring, and buffers are already in the
> context (napi) where they would be consumed from. Removes some
> headaches for the user (like batching before returning buffers),
> and should go better with smaller buffers and such.
> 
>> I also do not understand why the ifq cache 
> 
> I'm not sure what you mean by ifq cache. Can you elaborate?
> 
>> and overloading xdp functions
> 
> Assuming it's about setup via xdp, it was marked for remaking in
> RFCs for longer than desired but it's gone now in our tree (but
> maybe not in the latest series).
> 
>> have stuck around; I always thought both were added by Jonathan to
>> simplify kernel ports during early POC days.
> 

-- 
Pavel Begunkov

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