linux-kernel - Re: [PATCH net-next v4 5/5] page_pool: update document about frag API

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Message-ID: <7b426283-09f7-a16f-61b8-43319cdab27f@huawei.com>
Date:   Thu, 15 Jun 2023 14:49:03 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     <davem@...emloft.net>, <pabeni@...hat.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        <linux-doc@...r.kernel.org>, <bpf@...r.kernel.org>
Subject: Re: [PATCH net-next v4 5/5] page_pool: update document about frag API

On 2023/6/15 0:56, Jakub Kicinski wrote:
> On Wed, 14 Jun 2023 20:04:39 +0800 Yunsheng Lin wrote:
>>> Seems like the semantics of page_pool_alloc() are always better than
>>> page_pool_alloc_frag(). Is there a reason to keep these two separate?  
>>
>> I am agree the semantics of page_pool_alloc() is better, I was thinking
>> about combining those two too.
>> The reason I am keeping it is about the nic hw with fixed buffer size for
>> each desc, and that buffer size is always smaller than or equal to half
>> of the page allocated from page pool, so it doesn't bother doing the
>> checking of 'size << 1 > max_size' and doesn't care about the actual
>> truesize.
> 
> I see. Let's reorg the documentation, then? Something along the lines
> of, maybe:

There is still one thing I am not sure about page_pool_alloc() API:
It use *size both as input and output, I am not sure if it is a general
pratice or not, or is there other better pratice than this.