Re: [Intel-wired-lan] [PATCH net-next v2 1/6] net: ethtool: allow symmetric RSS hash for any flow type

[Ahmed Zaki <ahmed.zaki@intel.com>]

On 2023-10-07 03:01, Willem de Bruijn wrote:
> On Fri, Oct 6, 2023 at 7:22 PM Jakub Kicinski <kuba@kernel.org> wrote:
>> On Fri,  6 Oct 2023 16:47:21 -0600 Ahmed Zaki wrote:
>>> Symmetric RSS hash functions are beneficial in applications that monitor
>>> both Tx and Rx packets of the same flow (IDS, software firewalls, ..etc).
>>> Getting all traffic of the same flow on the same RX queue results in
>>> higher CPU cache efficiency.
>>>
>>> Only fields that has counterparts in the other direction can be
>>> accepted; IP src/dst and L4 src/dst ports.
>>>
>>> The user may request RSS hash symmetry for a specific flow type, via:
>>>
>>>      # ethtool -N|-U eth0 rx-flow-hash <flow_type> s|d|f|n symmetric
>>>
>>> or turn symmetry off (asymmetric) by:
>>>
>>>      # ethtool -N|-U eth0 rx-flow-hash <flow_type> s|d|f|n
>> Thanks for the changes, code looks good!
>>
>> The question left unanswered is whether we should care about the exact
>> implementation of the symmetry (xor, xor duplicate, sort fields).
>> Toeplitz-based RSS is very precisely specified, so we may want to carry
>> that precision into the symmetric behavior. I have a weak preference
>> to do so... but no willingness to argue with you, so let me put Willem
>> on the spot and have him make a decision :)
> I do have a stronger willingness to argue, thanks ;-)
>
> Can we give a more precise name, such as symmetric-xor? In case
> another device would implement another mode, such as the symmetric
> toeplitz of __flow_hash_consistentify, it would be good to be able to
> discern the modes.

I agree that implementation matters. I changed "symmetric" to 
"symmetric-xor" in v3.

Thanks for the review.


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