Re: [PATCH V7 net-next 0/6] ethtool: add support to set/get tx copybreak buf size and rx buf len

[Yunsheng Lin <linyunsheng@huawei.com>]

On 2022/10/27 17:03, Gal Pressman wrote:
> On 27/10/2022 03:49, Yunsheng Lin wrote:
>> On 2022/10/26 22:00, Gal Pressman wrote:
>>> On 18/11/2021 14:12, Guangbin Huang wrote:
>>>> From: Hao Chen <chenhao288@hisilicon.com>
>>>>
>>>> This series add support to set/get tx copybreak buf size and rx buf len via
>>>> ethtool and hns3 driver implements them.
>>>>
>>>> Tx copybreak buf size is used for tx copybreak feature which for small size
>>>> packet or frag. Use ethtool --get-tunable command to get it, and ethtool
>>>> --set-tunable command to set it, examples are as follow:
>>>>
>>>> 1. set tx spare buf size to 102400:
>>>> $ ethtool --set-tunable eth1 tx-buf-size 102400
>>>>
>>>> 2. get tx spare buf size:
>>>> $ ethtool --get-tunable eth1 tx-buf-size
>>>> tx-buf-size: 102400
>>> Hi Guangbin,
>>> Can you please clarify the difference between TX copybreak and TX
>>> copybreak buf size?
>> Hi Gal,
>> 'TX copybreak buf size' is the size of buffer allocated to a queue
>> in order to support copybreak handling when skb->len <= 'TX copybreak',
>>
>> see hns3_can_use_tx_bounce() for 'TX copybreak' and
>> hns3_init_tx_spare_buffer() for 'TX copybreak buf size'.
> 
> Thanks Yunsheng!
> IIUC, there's a single buffer per TX queue, not per TX packet, correct?

Yes.

> 
> One way to implement TX copybreak is using an inline WQE, where the WQE
> itself serves as the bounce buffer, sounds like 'TX copybreak buf size'
> cannot be used in such case?

If TX copybreak is using an inline WQE, I suppose 'TX copybreak buf size'
is not needed.

> .
>