Re: [PATCH v2 1/2] ethdev: add new symmetric hash function

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

在 2023/8/30 16:38, Xueming(Steven) Li 写道:
>
>> -----Original Message-----
>> From: lihuisong (C) <lihuisong@huawei.com>
>> Sent: 8/30/2023 15:51
>> To: Xueming(Steven) Li <xuemingl@nvidia.com>; Ori Kam <orika@nvidia.com>
>> Cc: dev@dpdk.org; fengchengwen@huawei.com; Ivan Malov
>> <ivan.malov@arknetworks.am>
>> Subject: Re: [PATCH v2 1/2] ethdev: add new symmetric hash function
>>
>> Hi Xueming,
>>
>> 在 2023/8/27 16:17, Xueming Li 写道:
>>> 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 | 7 +++++++
>>>    1 file changed, 7 insertions(+)
>>>
>>> diff --git a/lib/ethdev/rte_flow.h b/lib/ethdev/rte_flow.h index
>>> 2ebb76dbc0..4f4421ca50 100644
>>> --- a/lib/ethdev/rte_flow.h
>>> +++ b/lib/ethdev/rte_flow.h
>>> @@ -3196,6 +3196,13 @@ enum rte_eth_hash_function {
>>>    	 * src or dst address will xor with zero pair.
>>>    	 */
>>>    	RTE_ETH_HASH_FUNCTION_SYMMETRIC_TOEPLITZ,
>>> +	/**
>>> +	 * Symmetric Toeplitz: L3 and L4 fields are sorted prior to
>>> +	 * the hash function.
>>> +	 *  If src_ip > dst_ip, swap src_ip and dst_ip.
>>> +	 *  If src_port > dst_port, swap src_port and dst_port.
>>> +	 */
>> If hash result are computed by the order: "src_ip+dst_ip+src_port+dst_port"
>> How to obtain the value of every L3 and L4 field obove?
>> I still cannot understand how to swap and set these values for these fields?
> Hash result is computed by order ""src_ip+dst_ip+src_port+dst_port"
> Here is a detailed explanation of standard hash and symmetric hash by key:
>    https://www.ndsl.kaist.edu/~kyoungsoo/papers/TR-symRSS.pdf
>
> If src_ip > dst_ip, swap them, then the input becomes:
>    "dst_ip+src_ip+src_port+dst_port" // please note src and dst IP are swapped.
> Same for L4 ports.
get it.
What are the advantages of the symmetric toeplitz sort?
Or why swap here?
>
>>> +	RTE_ETH_HASH_FUNCTION_SYMMETRIC_TOEPLITZ_SORT,
>>>    	RTE_ETH_HASH_FUNCTION_MAX,
>>>    };
>>>