Re: [PATCH] ethdev: add new symmetric hash function

[fengchengwen <fengchengwen@huawei.com>]

On 2023/8/8 6:32, Ivan Malov wrote:
> Hi,
> 
> Please see my notes below.
> 
> On Mon, 7 Aug 2023, Xueming Li wrote:
> 
>> The new symmetric hash function swap src/dst L3 address and
>> L4 ports automatically by sorting.
>>
>> Signed-off-by: Xueming Li <xuemingl@nvidia.com>
>> ---
>> lib/ethdev/rte_flow.h | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/lib/ethdev/rte_flow.h b/lib/ethdev/rte_flow.h
>> index 86ed98c562..ec6dd170b5 100644
>> --- a/lib/ethdev/rte_flow.h
>> +++ b/lib/ethdev/rte_flow.h
>> @@ -3204,6 +3204,11 @@ enum rte_eth_hash_function {
>>      * src or dst address will xor with zero pair.
>>      */
>>     RTE_ETH_HASH_FUNCTION_SYMMETRIC_TOEPLITZ,
>> +    /**
>> +     * Symmetric Toeplitz: src, dst will be swapped
>> +     * automatically by sorting.
> 
> This is very vague. Consider:
> 
> For symmetric Toeplitz, four inputs are prepared as follows:
> - src_addr | dst_addr
> - src_addr ^ dst_addr
> - src_port | dst_port
> - src_port ^ dst_port
> and then passed to the regular Toeplitz function.
> 
> It is important to be as specific as possible
> so that readers don't have to guess.

+1 for this, I try to understand and google it, but can't find useful info.

Also, how this new algo with src/dst only ?

> 
> Thank you.
> 
>> +     */
>> +    RTE_ETH_HASH_FUNCTION_SYMMETRIC_TOEPLITZ_SORT,
>>     RTE_ETH_HASH_FUNCTION_MAX,

The new value will break the definition of MAX (maybe ABI compatible).
but I found only hns3 drivers use RTE_ETH_HASH_FUNCTION_MAX, not sure the application will use it.

>> };
>>
>> -- 
>> 2.25.1
>>
>>
> 
> .