From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BC09212C490; Wed, 1 May 2024 13:59:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714571957; cv=none; b=J3nv4JNhCH3zr/s7JdeCsI2Z5LuWf1arbxDg7Qyw7WRs8NW/s+Ms+ZHv1rgylDWWOPIEg7X1kQ0Ich2HQzQ+nboY35WZXfcQc7sKgsxTfa8x/5sXx2f+pVpQnKr9XRTaacybTZNig9nm+QFiRTEg5LGAeJjQFINFafgtD1bON2E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714571957; c=relaxed/simple; bh=Fi4PvMRZrF9DXNpSOwwia/BblzTiRO6iyf1z/eVq1XU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NbchjvG3iRoD7tZsVbSHBC2VDA1pFY2cj3SWAp5gw7+QlIJJAkkhCxOyXperwsUU5+WmLLsJDxONdC8ykFbY6y9qB9qCS+FG6ugqs8QH6pC8ieafJ/cFNzvbEp2j2Hhzi3kO26lzjrgh3dVTN/naxrWwGNw4DCa+GCEq30m/AXM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sCbrUaES; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="sCbrUaES" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B3C7C072AA; Wed, 1 May 2024 13:59:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1714571956; bh=Fi4PvMRZrF9DXNpSOwwia/BblzTiRO6iyf1z/eVq1XU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=sCbrUaESax+zNwmTNdY7otL0UFOQLPT1tCLvxhS1E2UCWFKHW4CFOG8eHXGAPEzYV K59HSeGnESqWuVyypeDsfjxCGIwlrkTiIB8RtlSIeODJISpG+bjrjqgUZTNnVYoXFo 0nAjOD3kay/wsGxmwOPaAc5VD0eUhuiBlauj3Z2WQisvO7reiDxOn7qiXguQyswbXz eGzZQLUgdh76hRrtTEFJVQdEHnMA2UjgtwHVl2z9L4Tsb3ZTSE/wBE57PdTiTs8Ocp FhNUI+PSuIOyAwwjpVUsbAi1uNR+QWMI+7HqtFjSwPStPFYwbkZKYGKHcbZk0YZOQW CZlqUKG4oenXA== Message-ID: <779b9542-4170-483a-af54-ca0dd471f774@kernel.org> Date: Wed, 1 May 2024 15:58:59 +0200 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH net-next v8 07/14] page_pool: devmem support To: Jens Axboe , Mina Almasry Cc: David Wei , 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" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jonathan Corbet , Richard Henderson , Ivan Kokshaysky , Matt Turner , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Andreas Larsson , Ilias Apalodimas , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Arnd Bergmann , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Steffen Klassert , Herbert Xu , David Ahern , Willem de Bruijn , Shuah Khan , Sumit Semwal , =?UTF-8?Q?Christian_K=C3=B6nig?= , Amritha Nambiar , Maciej Fijalkowski , Alexander Mikhalitsyn , Kaiyuan Zhang , Christian Brauner , Simon Horman , David Howells , Florian Westphal , Yunsheng Lin , Kuniyuki Iwashima , Arseniy Krasnov , Aleksander Lobakin , Michael Lass , Jiri Pirko , Sebastian Andrzej Siewior , Lorenzo Bianconi , Richard Gobert , Sridhar Samudrala , Xuan Zhuo , Johannes Berg , Abel Wu , Breno Leitao , Pavel Begunkov , Jason Gunthorpe , Shailend Chand , Harshitha Ramamurthy , Shakeel Butt , Jeroen de Borst , Praveen Kaligineedi , linux-mm@kvack.org, Matthew Wilcox References: <20240403002053.2376017-1-almasrymina@google.com> <20240403002053.2376017-8-almasrymina@google.com> <8357256a-f0e9-4640-8fec-23341fc607db@davidwei.uk> <11f52113-7b67-4b45-ba1d-29b070050cec@kernel.dk> Content-Language: en-US From: Jesper Dangaard Brouer In-Reply-To: <11f52113-7b67-4b45-ba1d-29b070050cec@kernel.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 30/04/2024 20.55, Jens Axboe wrote: > On 4/30/24 12:29 PM, Mina Almasry wrote: >> On Tue, Apr 30, 2024 at 6:46?AM Jens Axboe wrote: [...] >>> 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. >>> >> The history there is that this check adds 1 cycle regression to the >> page_pool fast path benchmark. The regression last I measured is 8->9 >> cycles, so in % wise it's a quite significant 12.5% (more details in >> the cover letter[1]). I doubt I can do much better than that to be >> honest. > > I'm all for cycle counting, and do it myself too, but is that even > measurable in anything that isn't a super targeted microbenchmark? Or > even in that? The reason for page_pool fast path being critical is that it is used for the XDP_DROP use-case. E.g on Mellanox mlx5 driver we see 24 Mpps XDP_DROP, which is approx 42 nanosec per packet. Adding 9 nanosec will reduce this to 19.6 Mpps. 1/(42+9)*10^9 = 19607843 --Jesper p.s. Upstreaming my PP microbenchmark[1] is still at the bottom of my todo-list. [1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/lib/bench_page_pool_simple.c