On Tue, 6 Apr 2021 20:50:40 +0100 Vladimir Medvedkin <vladimir.medved...@intel.com> wrote:
> This patch series introduces predictable RSS feature. > It is based on the idea of searching for partial hash collisions > within Toeplitz hash. > > The Toeplitz hash function is a homomorphism between (G, ^) and (H, ^), > where (G, ^) - is a group of tuples and (H, ^) is a group of hashes > with respect to XOR operation. So tuples and hashes could be treated as > n-dimension and 32-dimension vector spaces over GF(2). > So, f(x ^ y) == f(x) ^ f(y) > where f - is the toeplitz hash function and x, y are tuples. > > The ability to predict partial collisions allows user to compute > input hash value with desired LSB values. > Usually number of LSB's are defined by the size of RSS Redirection Table. > > There could be number of use cases, for example: > 1) NAT. Using this library it is possible to select a new port number > on a translation in the way that rss hash for original tuple will have > the same LSB's as rss hash for reverse tuple. > 2) IPSec/MPLS/Vxlan. It is possible to choose tunnel id to be pinned to > a desired queue. > 3) TCP stack. It is possible to choose a source port number for outgoing > connections in the way that received replies will be assigned to > desired queue. > 4) RSS hash key generation. Hash key initialization with random values > does not guarantee an uniform distribution amongst queues. This library > uses mathematically proved algorithm to complete the rss hash key to > provide the best distribution. > > v2: > - added extra API rte_thash_adjust_tuple() > - added extra tests for rte_thash_adjust_tuple() > - added extra fields to rte_thash_subtuple_helper struct > - fixed typos > > Vladimir Medvedkin (3): > hash: add predictable RSS API > hash: add predictable RSS implementation > test/hash: add additional thash tests > > app/test/test_thash.c | 468 +++++++++++++++++++++++++++++++- > lib/librte_hash/meson.build | 3 +- > lib/librte_hash/rte_thash.c | 637 > ++++++++++++++++++++++++++++++++++++++++++++ > lib/librte_hash/rte_thash.h | 180 +++++++++++++ > lib/librte_hash/version.map | 8 + > 5 files changed, 1289 insertions(+), 7 deletions(-) > create mode 100644 lib/librte_hash/rte_thash.c > It would be good to show how this could be used in an application. Maybe yet another variant/flag to l3fwd example.