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

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Message-ID: <b1438638-a6f9-4a88-b8fe-7bec28ba124f@intel.com>
Date: Wed, 10 Apr 2024 15:01:26 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Przemek Kitszel <przemyslaw.kitszel@...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

From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
Date: Wed, 10 Apr 2024 15:01:32 +0200

> 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`

In the commit:

+ * struct libeth_fqe - structure representing an Rx buffer

:z

or you want me to expand FQ, FQE etc. abbrevs in the kdoc?

Thanks,
Olek