netdev - Re: [RFC PATCH net-next v8 07/14] page

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <aafbbf09-a33d-4e73-99c8-9ddab5910657@kernel.dk>
Date: Tue, 30 Apr 2024 07:45:52 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Mina Almasry <almasrymina@...gle.com>, David Wei <dw@...idwei.uk>
Cc: 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>, 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>,
 David Ahern <dsahern@...nel.org>,
 Willem de Bruijn <willemdebruijn.kernel@...il.com>,
 Shuah Khan <shuah@...nel.org>, Sumit Semwal <sumit.semwal@...aro.org>,
 Christian König <christian.koenig@....com>,
 Amritha Nambiar <amritha.nambiar@...el.com>,
 Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
 Alexander Mikhalitsyn <alexander@...alicyn.com>,
 Kaiyuan Zhang <kaiyuanz@...gle.com>, Christian Brauner <brauner@...nel.org>,
 Simon Horman <horms@...nel.org>, David Howells <dhowells@...hat.com>,
 Florian Westphal <fw@...len.de>, Yunsheng Lin <linyunsheng@...wei.com>,
 Kuniyuki Iwashima <kuniyu@...zon.com>,
 Arseniy Krasnov <avkrasnov@...utedevices.com>,
 Aleksander Lobakin <aleksander.lobakin@...el.com>,
 Michael Lass <bevan@...co.net>, Jiri Pirko <jiri@...nulli.us>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Lorenzo Bianconi <lorenzo@...nel.org>,
 Richard Gobert <richardbgobert@...il.com>,
 Sridhar Samudrala <sridhar.samudrala@...el.com>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
 Johannes Berg <johannes.berg@...el.com>, Abel Wu <wuyun.abel@...edance.com>,
 Breno Leitao <leitao@...ian.org>, Pavel Begunkov <asml.silence@...il.com>,
 Jason Gunthorpe <jgg@...pe.ca>, 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>,
 linux-mm@...ck.org, Matthew Wilcox <willy@...radead.org>
Subject: Re: [RFC PATCH net-next v8 07/14] page_pool: devmem support

On 4/26/24 8:11 PM, Mina Almasry wrote:
> On Fri, Apr 26, 2024 at 5:18?PM David Wei <dw@...idwei.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.

In general, attempting to hide overhead behind config options is always
a losing proposition. It merely serves to say "look, if these things
aren't enabled, the overhead isn't there", while distros blindly enable
pretty much everything and then you're back where you started.

-- 
Jens Axboe