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

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Message-ID: <cacde7b2-6bc4-bd30-8cd3-6f802c737ce5@gmail.com>
Date:   Mon, 7 Jun 2021 14:14:09 +0300
From:   Tariq Toukan <ttoukan.linux@...il.com>
To:     Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc:     Matteo Croce <mcroce@...ux.microsoft.com>,
        David Ahern <dsahern@...il.com>,
        Yunsheng Lin <linyunsheng@...wei.com>, netdev@...r.kernel.org,
        linux-mm@...ck.org, Ayush Sawal <ayush.sawal@...lsio.com>,
        Vinay Kumar Yadav <vinay.yadav@...lsio.com>,
        Rohit Maheshwari <rohitm@...lsio.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Russell King <linux@...linux.org.uk>,
        Mirko Lindner <mlindner@...vell.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Tariq Toukan <tariqt@...dia.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Boris Pismenny <borisp@...dia.com>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>, Yu Zhao <yuzhao@...gle.com>,
        Will Deacon <will@...nel.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Roman Gushchin <guro@...com>, Hugh Dickins <hughd@...gle.com>,
        Peter Xu <peterx@...hat.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexander Lobakin <alobakin@...me>,
        Cong Wang <cong.wang@...edance.com>, wenxu <wenxu@...oud.cn>,
        Kevin Hao <haokexin@...il.com>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Marco Elver <elver@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Guillaume Nault <gnault@...hat.com>,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        bpf@...r.kernel.org, Matthew Wilcox <willy@...radead.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Saeed Mahameed <saeedm@...dia.com>,
        Andrew Lunn <andrew@...n.ch>, Paolo Abeni <pabeni@...hat.com>,
        Sven Auhagen <sven.auhagen@...eatech.de>
Subject: Re: [PATCH net-next v6 3/5] page_pool: Allow drivers to hint on SKB
 recycling



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