Wednesday, July 31, 2019 3:31 PM, Adrien Mazarguil: > Subject: Re: [dpdk-dev] [PATCH 1/2] ethdev: add symmetric toeplitz hash > support > > On Wed, Jul 31, 2019 at 03:08:19PM +0300, Andrew Rybchenko wrote: > > On 7/25/19 7:57 AM, simei wrote: > > > From: Simei Su <simei...@intel.com> > > > > > > Currently, there are DEFAULT,TOEPLITZ and SIMPLE_XOR hash funtion. > > > To support symmetric hash by rte_flow RSS action, this patch adds > > > new hash function "Symmetric Toeplitz" which is supported by some > hardware. > > > > Isn't it a question of key to achieve symmetry? > > I.e. hash algorithm (function) is still the same - Toeplitz, but hash > > key makes the result symmetric (i.e. equal for flows in both > > directions - swap transport ports and IPv4/6 addresses). > > This is only an option when src/dst are known in advance. > > When doing RSS, HW implementations (such as Mellanox's) implement a > modified Toeplitz XOR'ing src with dst resulting in the same hash both ways > regardless of the key.
Just to stand correct it was a bug on Mellanox kernel driver that was fixed. Now the RSS is spec complaint (non-symmetric). Andrew is correct one can have a special key that will make the RSS symmetric, however it is good to have this option for the user to explicitly request symmetric function (w/o any restriction on the key). > > -- > Adrien Mazarguil > 6WIND
