Re: [PATCH v3 1/6] doc: add RSS hash algorithm feature

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 11/27/2023 1:12 PM, lihuisong (C) wrote:
> 
> 在 2023/11/27 20:19, Ferruh Yigit 写道:
>> On 11/25/2023 1:47 AM, Huisong Li wrote:
>>> Add hash algorithm feature introduced by 23.11 and fix some RSS features
>>> description.
>>>
>>> Fixes: 34ff088cc241 ("ethdev: set and query RSS hash algorithm")
>>>
>>> Signed-off-by: Huisong Li <lihuisong@huawei.com>
>>> Acked-by: Chengwen Feng <fengchengwen@huawei.com>
>>> ---
>>>   doc/guides/nics/features.rst | 26 ++++++++++++++++++++++----
>>>   1 file changed, 22 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/doc/guides/nics/features.rst b/doc/guides/nics/features.rst
>>> index 1a1dc16c1e..0d38c5c525 100644
>>> --- a/doc/guides/nics/features.rst
>>> +++ b/doc/guides/nics/features.rst
>>> @@ -277,10 +277,12 @@ RSS hash
>>>   Supports RSS hashing on RX.
>>>     * **[uses]     user config**: ``dev_conf.rxmode.mq_mode`` =
>>> ``RTE_ETH_MQ_RX_RSS_FLAG``.
>>> -* **[uses]     user config**: ``dev_conf.rx_adv_conf.rss_conf``.
>>> +* **[uses]     user config**: ``rss_conf.rss_hf``.
>>>
>> Feature title is "RSS hash", it can be two things,
>> 1. "Receive Side Scaling" support
>> 2. Provide RSS hash to application
>>
>> When this document first prepared RSS hash value was always provided to
>> the application when RSS enabled.
>> So intention with this feature was "Receive Side Scaling" support, hence
>> 'RTE_ETH_MQ_RX_RSS_FLAG' added.
>>
>> Later providing RSS has to the application separated as optimization,
>> 'RTE_ETH_RX_OFFLOAD_RSS_HASH' & 'RTE_MBUF_F_RX_RSS_HASH' added for this
>> support.
> What should I do for above two comments？
> To tell application how to use it?
>

Just tried to give some context.


>>
>> As the intention of this feature is "Receive Side Scaling" support, we
>> shouldn't reduce configuration struct to 'rss_conf.rss_hf'.
>>
>> Instead perhaps can expand to:
>> 'rte_eth_conf.rx_adv_conf.rss_conf', 'rte_eth_rss_conf'
> 
>  I just pick their common part.😁
> 
> ok, will fix it.
> 
>>
>>
>>>   * **[uses]     rte_eth_rxconf,rte_eth_rxmode**:
>>> ``offloads:RTE_ETH_RX_OFFLOAD_RSS_HASH``.
>>>   * **[provides] rte_eth_dev_info**: ``flow_type_rss_offloads``.
>>>   * **[provides] mbuf**: ``mbuf.ol_flags:RTE_MBUF_F_RX_RSS_HASH``,
>>> ``mbuf.rss``.
>>> +* **[related]  API**: ``rte_eth_dev_configure``,
>>> ``rte_eth_dev_rss_hash_update``
>>> +  ``rte_eth_dev_rss_hash_conf_get()``.
>>>   
>> ack
>>
>>>     .. _nic_features_inner_rss:
>>> @@ -288,7 +290,7 @@ Supports RSS hashing on RX.
>>>   Inner RSS
>>>   ---------
>>>   -Supports RX RSS hashing on Inner headers.
>>> +Supports RX RSS hashing on Inner headers by rte_flow API.
>>>   
>> This should be clarified with details below, not sure if it required to
>> limit description to rte_flow.
> But this block like rte_flow_action_rss is from rte_flow.
> And ethdev ops doesn't support inner RSS.
> So I think it is ok.
>

Yes it is supported by rte_flow, and '[uses]' information should already
clarify it.


>>
>>
>> And I guess similar confusion exist with the providing hash to user.
>> Need to check if rte_flow implementation puts hash to mbuf along with
>> doing the RSS, or if it checks 'RTE_ETH_RX_OFFLOAD_RSS_HASH' offload,
>> and update below items accordingly.
> Do we need to tell user how to use it here?
> I feel this document is a little simple and main to list interface for
> user.
> In addition, it is better that the more detail about RSS should be
> presented  in rte_flow features.
>

No, I am not suggesting to add more detail.

My concern is 'RTE_ETH_RX_OFFLOAD_RSS_HASH' information may not be
correct, ethdev APIs checks offload flags, but does rte_flow
implementation check it?

My suggestion is double check that piece of information and fix it if
required.


>>
>>
>>>   * **[uses]    rte_flow_action_rss**: ``level``.
>>>   * **[uses]    rte_eth_rxconf,rte_eth_rxmode**:
>>> ``offloads:RTE_ETH_RX_OFFLOAD_RSS_HASH``.
>>> @@ -303,9 +305,25 @@ RSS key update
>>>   Supports configuration of Receive Side Scaling (RSS) hash
>>> computation. Updating
>>>   Receive Side Scaling (RSS) hash key.
>>>   -* **[implements] eth_dev_ops**: ``rss_hash_update``,
>>> ``rss_hash_conf_get``.
>>> +* **[implements] eth_dev_ops**: ``dev_configure``,
>>> ``rss_hash_update``, ``rss_hash_conf_get``.
>>> +* **[uses]     user config**: ``rss_conf.rss_key``,
>>> ``rss_conf.rss_key_len``
>>>   * **[provides]   rte_eth_dev_info**: ``hash_key_size``.
>>> -* **[related]    API**: ``rte_eth_dev_rss_hash_update()``,
>>> +* **[related]    API**: ``rte_eth_dev_configure``,
>>> ``rte_eth_dev_rss_hash_update()``,
>>> +  ``rte_eth_dev_rss_hash_conf_get()``.
>>> +
>> ack
>>
>> There is an inconsistency in the documentation but I think it is good to
>> use '()' when documenting API, like: 'rte_eth_dev_configure()'
> +1 will fix it.
>>
>>
>>> +
>>> +.. _nic_features_rss_hash_algo_update:
>>> +
>>> +RSS hash algorithm update
>>> +-------------------------
>>> +
>>> +Supports configuration of Receive Side Scaling (RSS) hash algorithm.
>>> Updating
>>> +RSS hash algorithm.
>>> +
>>> +* **[implements] eth_dev_ops**: ``dev_configure``,
>>> ``rss_hash_update``, ``rss_hash_conf_get``.
>>> +* **[uses]     user config**: ``rss_conf.algorithm``
>>> +* **[provides]   rte_eth_dev_info**: ``rss_algo_capa``.
>>> +* **[related]    API**: ``rte_eth_dev_configure``,
>>> ``rte_eth_dev_rss_hash_update()``,
>>>     ``rte_eth_dev_rss_hash_conf_get()``.
>>>     
>>
>> This document describes features listed in the 'default.ini', so we
>> shouldn't have above.
>>
>> And I don't think RSS hash algorithm update is a big enough feature to
>> list in the feature list, perhaps it can be embedded in the RSS support
>> block, what do you think?
> Yes it is not a bit feature.
> so put it to RSS hash, right?
> 

Yes please.