Re: [PATCH net-next v6 3/5] page_pool: Allow drivers to hint on SKB recycling

From: Tariq Toukan <ttoukan.linux@gmail.com>
To: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc: Matteo Croce <mcroce@linux.microsoft.com>,
	David Ahern <dsahern@gmail.com>,
	Yunsheng Lin <linyunsheng@huawei.com>,
	netdev@vger.kernel.org, linux-mm@kvack.org,
	Ayush Sawal <ayush.sawal@chelsio.com>,
	Vinay Kumar Yadav <vinay.yadav@chelsio.com>,
	Rohit Maheshwari <rohitm@chelsio.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Marcin Wojtas <mw@semihalf.com>,
	Russell King <linux@armlinux.org.uk>,
	Mirko Lindner <mlindner@marvell.com>,
	Stephen Hemminger <stephen@networkplumber.org>,
	Tariq Toukan <tariqt@nvidia.com>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
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	Andrew Morton <akpm@linux-foundation.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
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	Willem de Bruijn <willemb@google.com>,
	Miaohe Lin <linmiaohe@huawei.com>,
	Guillaume Nault <gnault@redhat.com>,
	linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
	bpf@vger.kernel.org, Matthew Wilcox <willy@infradead.org>,
	Eric Dumazet <edumazet@google.com>,
	Lorenzo Bianconi <lorenzo@kernel.org>,
	Saeed Mahameed <saeedm@nvidia.com>, Andrew Lunn <andrew@lunn.ch>,
	Paolo Abeni <pabeni@redhat.com>,
	Sven Auhagen <sven.auhagen@voleatech.de>
Subject: Re: [PATCH net-next v6 3/5] page_pool: Allow drivers to hint on SKB recycling
Date: Mon, 7 Jun 2021 14:14:09 +0300	[thread overview]
Message-ID: <cacde7b2-6bc4-bd30-8cd3-6f802c737ce5@gmail.com> (raw)
In-Reply-To: <YL2i0wcXcqluttNx@Iliass-MBP>


On 6/7/2021 7:38 AM, Ilias Apalodimas wrote:
> Hi Tariq,
> 
>>>>>
>>>>> Yes the comment is there to prohibit people (mlx5 only actually) to add the
>>>>> recycling bit on their driver.  Because if they do it will *probably* work
>>>>> but they might get random corrupted packets which will be hard to debug.
>>>>>
>>>>
>>>> What's the complexity for getting it to work with split page model?
>>>> Since 1500 is the default MTU, requiring a page per packet means a lot
>>>> of wasted memory.
>>>
>>> We could create a new memory model, e.g. MEM_TYPE_PAGE_SPLIT, and
>>> restore the behavior present in the previous versions of this serie,
>>> which is, save xdp_mem_info in struct page.
>>> As this could slightly impact the performances, this can be added in a
>>> future change when the drivers which are doing it want to use this
>>> recycling api.
>>>
>>
>> page-split model doesn't only help reduce memory waste, but increase
>> cache-locality, especially for aggregated GRO SKBs.
>>
>> I'm looking forward to integrating the page-pool SKB recycling API into
>> mlx5e datapath. For this we need it to support the page-split model.
>>
>> Let's see what's missing and how we can help making this happen.
> 
> Yes that's the final goal.  As I said I don't think adding the page split
> model will fundamentally change the current patchset.  So imho we should
> get this in first, make sure that everything is fine, and then add code for
> the mlx cards.
> 

Sounds good