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Subject: Re: [PATCH net-next v6 3/5] page_pool: Allow drivers to hint on SKB
 recycling
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>,
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        Russell King <linux@armlinux.org.uk>,
        Mirko Lindner <mlindner@marvell.com>,
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        Tariq Toukan <tariqt@nvidia.com>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
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 <63a4ea45-9938-3106-9eda-0f7e8fe079ce@gmail.com>
 <YL2i0wcXcqluttNx@Iliass-MBP>
From:   Tariq Toukan <ttoukan.linux@gmail.com>
Message-ID: <cacde7b2-6bc4-bd30-8cd3-6f802c737ce5@gmail.com>
Date:   Mon, 7 Jun 2021 14:14:09 +0300
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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