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

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Date: Tue, 9 Apr 2024 12:58:33 +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 4/8/24 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 ;)

>>
>> otherwise the whole series is very good for me, thank you very much!
>>
> 
> Thanks,
> Olek