[dpdk-dev] [PATCH v1 0/3] Predictable RSS feature

Vladimir Medvedkin vladimir.medvedkin at intel.com
Tue Mar 16 19:24:34 CET 2021


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.

Vladimir Medvedkin (3):
  hash: add predictable RSS API
  hash: add predictable RSS implementation
  test/hash: add additional thash tests

 app/test/test_thash.c       | 383 +++++++++++++++++++++++++++-
 lib/librte_hash/meson.build |   3 +-
 lib/librte_hash/rte_thash.c | 596 ++++++++++++++++++++++++++++++++++++++++++++
 lib/librte_hash/rte_thash.h | 138 ++++++++++
 lib/librte_hash/version.map |   7 +
 5 files changed, 1120 insertions(+), 7 deletions(-)
 create mode 100644 lib/librte_hash/rte_thash.c

-- 
2.7.4



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