netdev - Re: [PATCH net-next v9 7/9] libeth: add Rx buffer management

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Message-ID: <61a952aa-1b3e-43c7-9f35-ab53e492305a@intel.com>
Date: Wed, 10 Apr 2024 15:01:32 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
CC: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, Alexander Duyck <alexanderduyck@...com>, Yunsheng Lin
	<linyunsheng@...wei.com>, Jesper Dangaard Brouer <hawk@...nel.org>, "Ilias
 Apalodimas" <ilias.apalodimas@...aro.org>, Christoph Lameter <cl@...ux.com>,
	Vlastimil Babka <vbabka@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>,
	<nex.sw.ncis.osdt.itp.upstreaming@...el.com>, <netdev@...r.kernel.org>,
	<intel-wired-lan@...ts.osuosl.org>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v9 7/9] libeth: add Rx buffer management

On 4/10/24 13:49, Alexander Lobakin wrote:
> From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
> Date: Tue, 9 Apr 2024 12:58:33 +0200
> 
>> On 4/8/24 11:09, Alexander Lobakin wrote:
>>> From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
>>> Date: Fri, 5 Apr 2024 12:32:55 +0200
>>>
>>>> On 4/4/24 17:44, Alexander Lobakin wrote:
>>>>> Add a couple intuitive helpers to hide Rx buffer implementation details
>>>
>>> [...]
>>>
>>>>> +struct libeth_fqe {
>>>>> +    struct page        *page;
>>>>> +    u32            offset;
>>>>> +    u32            truesize;
>>>>> +} __aligned_largest;
>>>>> +
>>>>> +/**
>>>>> + * struct libeth_fq - structure representing a buffer queue
>>>>> + * @fp: hotpath part of the structure
>>>>> + * @pp: &page_pool for buffer management
>>>>> + * @fqes: array of Rx buffers
>>>>> + * @truesize: size to allocate per buffer, w/overhead
>>>>> + * @count: number of descriptors/buffers the queue has
>>>>> + * @buf_len: HW-writeable length per each buffer
>>>>> + * @nid: ID of the closest NUMA node with memory
>>>>> + */
>>>>> +struct libeth_fq {
>>>>> +    struct_group_tagged(libeth_fq_fp, fp,
>>>>> +        struct page_pool    *pp;
>>>>> +        struct libeth_fqe    *fqes;
>>>>> +
>>>>> +        u32            truesize;
>>>>> +        u32            count;
>>>>> +    );
>>>>> +
>>>>> +    /* Cold fields */
>>>>> +    u32            buf_len;
>>>>> +    int            nid;
>>>>> +};
>>>>
>>>> [...]
>>>>
>>>> Could you please unpack the meaning of `fq` and `fqe` acronyms here?
>>>
>>> Rx:
>>>
>>> RQ -- receive queue, on which you get Rx DMA complete descriptors
>>> FQ -- fill queue, the one you fill with free buffers
>>>     FQE -- fill queue element, i.e. smth like "iavf_rx_buffer" or whatever
>>>
>>> Tx:
>>>
>>> SQ -- send queue, the one you fill with buffers to transmit
>>>     SQE -- send queue element, i.e. "iavf_tx_buffer"
>>> CQ -- completion queue, on which you get Tx DMA complete descriptors
>>>
>>> XDPSQ, XSkRQ etc. -- same as above, but for XDP / XSk
>>>
>>> I know that rxq, txq, bufq, complq is more common since it's been used
>>> for years, but I like these "new" ones more :>
>>>
>>
>> Thank you, that sounds right. If you happen to sent v10, a bit of code
>> comment with this info would be useful ;)
> 
> The current kdoc in front of each struct and function declaration is not
> enough? :D
> 
> Thanks,
> Olek

I've asked my initial question just after reading it thrice, without
your reply `FQE` was as meaningful as `ABC`