On Fri, Oct 6, 2023 at 7:22 PM Jakub Kicinski <kuba@xxxxxxxxxx> 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.
