Re: [PATCH 2/6] net/hns3: fix inconsistent enabled RSS behavior

["lihuisong (C)" <lihuisong@huawei.com>]

Thanks, Stephen.

在 2022/3/3 0:59, Stephen Hemminger 写道:
> On Wed, 02 Mar 2022 15:46:37 +0100
> Thomas Monjalon <thomas@monjalon.net> wrote:
>
>> 02/03/2022 15:07, Ori Kam:
>>> From: lihuisong (C) <lihuisong@huawei.com>
>>>> 在 2022/3/1 0:42, Ferruh Yigit 写道:
>>>>> On 2/28/2022 3:21 AM, Min Hu (Connor) wrote:
>>>>>> From: Huisong Li <lihuisong@huawei.com>
>>>>>>
>>>>>> RSS will not be enabled if the RTE_ETH_MQ_RX_RSS_FLAG isn't be set in
>>>>>> dev_configure phase. However, if this flag isn't set, RSS can be enabled
>>>>>> through the ethdev ops and rte_flow API. This behavior is contrary to
>>>>>> each
>>>>>> other.
>>>>>>
>>>>>> Fixes: c37ca66f2b27 ("net/hns3: support RSS")
>>>>>> Cc: stable@dpdk.org
>>>>>>
>>>>>> Signed-off-by: Huisong Li <lihuisong@huawei.com>
>>>>>
>>>>> Hi Huisong, Connor,
>>>>>
>>>>> Let's get a little more feedback for this patch, cc'ed more people.
>>>>>
>>>>>
>>>>> To enable RSS, multi queue mode should be set to
>>>>> 'RTE_ETH_MQ_RX_RSS_FLAG'.
>>>>>
>>>>> But I wonder if it is required to configure RSS via flow API,
>>>> I do not know the original purpose of adding the RSS configuration in
>>>> flow API.
>>>>    
>>> The purpose is simple, this allow to create RSS per rule and not a global one.
>>> For example create RSS that sends TCP to some queues while othe RSS will send
>>> UDP traffic to different queues.
>>>    
>>>> However, as far as I know, the hash algorithm can be configured via this
>>>> API,
>>>>
>>>> but not via ethdev ops API.
>>>>    
>>>>> and if other PMDs check this configuration for flow API?
>>>> Some PMDs already have similar check in RSS releated ops or rte_flow API.
>>>>
>>>> For example, hinic, axbge, bnxt, cnxk, otx2, and ena.
>> I suggest removing these checks.
>>
>>>  From my view point those are two different settings.
>>> The RTE_ETH_MQ_RX_RSS_FLAG is global per port while
>>> rte_flow is per rule.
>>>
>>> I think, that if a PMD needs this flag, in order to enable it also for rte_flow then
>>> it should be documented in the release note of the PMD.
>>> It is a valid use case that the default traffic will not have RSS and only rules created by
>>> rte_flow will have the RSS, for matching traffc.
>> I think RTE_ETH_MQ_RX_RSS_FLAG should not be required by any PMD
>> for rte_flow RSS rules.
>>
>>
> Agreed.
>
> The ideal state around RSS would be:
>     - global settings affect the default started queues when device is started.
>       if RSS is enabled and 4 queues are started, then RSS would happen for received
>       packets across those 4 queues.
>     - when adding new flow related rx:
>        - new queues could be started - BUT not part of original RSS
How should I understand this? If do this, we have to increase queue numbers.
>        - new rte_flow rule can do RSS against the new flow:
>              example:
>                start queues 4,5,6,7
>                rte_flow match TCP port 80 and process on queues 4,5,6,7 with RSS
I think you have the same view as Ori. But some original RSS hash 
configuration
has been overwritten by a new rule, such as redirection table.
>
> This is a mess today, most devices work differently and there is no reference software
> implementation.  In an ideal state, there would be a reference software implementation
> that implements all of rte_flow, and all new hardware support would have to work the same
> as the reference implementation. And there would be a full CI test suite around rte_flow.
> .