Received-SPF: pass (google.com: domain of linux-kernel+bounces-160868-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Precedence: bulk
MIME-Version: 1.0
References: <20240403002053.2376017-1-almasrymina@google.com>
 <20240403002053.2376017-8-almasrymina@google.com> <8357256a-f0e9-4640-8fec-23341fc607db@davidwei.uk>
In-Reply-To: <8357256a-f0e9-4640-8fec-23341fc607db@davidwei.uk>
From: Mina Almasry <almasrymina@google.com>
Date: Fri, 26 Apr 2024 19:11:07 -0700
Message-ID: <CAHS8izPeYryoLdCAQdGQU-wn7YVdtuofVKNvRFjFjhqTDsT7zA@mail.gmail.com>
Subject: Re: [RFC PATCH net-next v8 07/14] page_pool: devmem support
To: David Wei <dw@davidwei.uk>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, 
	linux-doc@vger.kernel.org, linux-alpha@vger.kernel.org, 
	linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, 
	sparclinux@vger.kernel.org, linux-trace-kernel@vger.kernel.org, 
	linux-arch@vger.kernel.org, bpf@vger.kernel.org, 
	linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org, 
	dri-devel@lists.freedesktop.org, "David S. Miller" <davem@davemloft.net>, 
	Eric Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>, 
	Jonathan Corbet <corbet@lwn.net>, Richard Henderson <richard.henderson@linaro.org>, 
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Matt Turner <mattst88@gmail.com>, 
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>, 
	"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>, Helge Deller <deller@gmx.de>, 
	Andreas Larsson <andreas@gaisler.com>, Jesper Dangaard Brouer <hawk@kernel.org>, 
	Ilias Apalodimas <ilias.apalodimas@linaro.org>, Steven Rostedt <rostedt@goodmis.org>, 
	Masami Hiramatsu <mhiramat@kernel.org>, Mathieu Desnoyers <mathieu.desnoyers@efficios.com>, 
	Arnd Bergmann <arnd@arndb.de>, Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, 
	Andrii Nakryiko <andrii@kernel.org>, Martin KaFai Lau <martin.lau@linux.dev>, 
	Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>, 
	Yonghong Song <yonghong.song@linux.dev>, John Fastabend <john.fastabend@gmail.com>, 
	KP Singh <kpsingh@kernel.org>, Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>, 
	Jiri Olsa <jolsa@kernel.org>, Steffen Klassert <steffen.klassert@secunet.com>, 
	Herbert Xu <herbert@gondor.apana.org.au>, David Ahern <dsahern@kernel.org>, 
	Willem de Bruijn <willemdebruijn.kernel@gmail.com>, Shuah Khan <shuah@kernel.org>, 
	Sumit Semwal <sumit.semwal@linaro.org>, =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>, 
	Amritha Nambiar <amritha.nambiar@intel.com>, 
	Maciej Fijalkowski <maciej.fijalkowski@intel.com>, 
	Alexander Mikhalitsyn <alexander@mihalicyn.com>, Kaiyuan Zhang <kaiyuanz@google.com>, 
	Christian Brauner <brauner@kernel.org>, Simon Horman <horms@kernel.org>, 
	David Howells <dhowells@redhat.com>, Florian Westphal <fw@strlen.de>, 
	Yunsheng Lin <linyunsheng@huawei.com>, Kuniyuki Iwashima <kuniyu@amazon.com>, Jens Axboe <axboe@kernel.dk>, 
	Arseniy Krasnov <avkrasnov@salutedevices.com>, 
	Aleksander Lobakin <aleksander.lobakin@intel.com>, Michael Lass <bevan@bi-co.net>, 
	Jiri Pirko <jiri@resnulli.us>, Sebastian Andrzej Siewior <bigeasy@linutronix.de>, 
	Lorenzo Bianconi <lorenzo@kernel.org>, Richard Gobert <richardbgobert@gmail.com>, 
	Sridhar Samudrala <sridhar.samudrala@intel.com>, Xuan Zhuo <xuanzhuo@linux.alibaba.com>, 
	Johannes Berg <johannes.berg@intel.com>, Abel Wu <wuyun.abel@bytedance.com>, 
	Breno Leitao <leitao@debian.org>, Pavel Begunkov <asml.silence@gmail.com>, 
	Jason Gunthorpe <jgg@ziepe.ca>, Shailend Chand <shailend@google.com>, 
	Harshitha Ramamurthy <hramamurthy@google.com>, Shakeel Butt <shakeel.butt@linux.dev>, 
	Jeroen de Borst <jeroendb@google.com>, Praveen Kaligineedi <pkaligineedi@google.com>, linux-mm@kvack.org, 
	Matthew Wilcox <willy@infradead.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Fri, Apr 26, 2024 at 5:18=E2=80=AFPM David Wei <dw@davidwei.uk> wrote:
>
> On 2024-04-02 5:20 pm, Mina Almasry wrote:
> > @@ -69,20 +106,26 @@ net_iov_binding(const struct net_iov *niov)
> >   */
> >  typedef unsigned long __bitwise netmem_ref;
> >
> > +static inline bool netmem_is_net_iov(const netmem_ref netmem)
> > +{
> > +#if defined(CONFIG_PAGE_POOL) && defined(CONFIG_DMA_SHARED_BUFFER)
>
> I am guessing you added this to try and speed up the fast path? It's
> overly restrictive for us since we do not need dmabuf necessarily. I
> spent a bit too much time wondering why things aren't working only to
> find this :(

My apologies, I'll try to put the changelog somewhere prominent, or
notify you when I do something that I think breaks you.

Yes, this is a by-product of a discussion with regards to the
page_pool benchmark regressions due to adding devmem. There is some
background on why this was added and the impact on the
bench_page_pool_simple tests in the cover letter.

For you, I imagine you want to change this to something like:

#if defined(CONFIG_PAGE_POOL)
#if defined(CONFIG_DMA_SHARED_BUFFER) || defined(CONFIG_IOURING)

or something like that, right? Not sure if this is something I should
do here or if something more appropriate to be in the patches you
apply on top.

I additionally think you may also need to run the
page_pool_benchmark_simple tests like I do in the cover letter to see
if you're affecting those.

--
Thanks,
Mina