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[0/5] riscv: implement accelerated crc using zbc

Message ID 20240618174133.33457-1-daniel.gregory@bytedance.com (mailing list archive)
Headers
Series riscv: implement accelerated crc using zbc |

Message

Daniel Gregory June 18, 2024, 5:41 p.m. UTC 
The RISC-V Zbc extension adds instructions for carry-less multiplication
we can use to implement CRC in hardware. This patchset contains two new
implementations:

- one in lib/hash/rte_crc_riscv64.h that uses a Barrett reduction to
  implement the four rte_hash_crc_* functions
- one in lib/net/net_crc_zbc.c that uses repeated single-folds to reduce
  the buffer until it is small enough for a Barrett reduction to
  implement rte_crc16_ccitt_zbc_handler and rte_crc32_eth_zbc_handler

My approach is largely based on the Intel's "Fast CRC Computation Using
PCLMULQDQ Instruction" white paper
https://www.researchgate.net/publication/263424619_Fast_CRC_computation
and a post about "Optimizing CRC32 for small payload sizes on x86"
https://mary.rs/lab/crc32/

These implementations are behind a new flag, RTE_RISCV_ZBC. Due to use
of bitmanip compiler intrinsics, a modern version of GCC (14+) or Clang
(18+) is required to compile with this flag enabled.

I have carried out some performance comparisons between the generic
table implementations and the new hardware implementations. Listed below
is the number of cycles it takes to compute the CRC hash for buffers of
various sizes (as reported by rte_get_timer_cycles()). These results
were collected on a Kendryte K230 and averaged over 20 samples:

|Buffer    | CRC32-ETH (lib/net) | CRC32C (lib/hash)   |
|Size (MB) | Table    | Hardware | Table    | Hardware |
|----------|----------|----------|----------|----------|
|        1 |   155168 |    11610 |    73026 |    18385 |
|        2 |   311203 |    22998 |   145586 |    35886 |
|        3 |   466744 |    34370 |   218536 |    53939 |
|        4 |   621843 |    45536 |   291574 |    71944 |
|        5 |   777908 |    56989 |   364152 |    89706 |
|        6 |   932736 |    68023 |   437016 |   107726 |
|        7 |  1088756 |    79236 |   510197 |   125426 |
|        8 |  1243794 |    90467 |   583231 |   143614 |

These results suggest a speed-up of lib/net by thirteen times, and of
lib/hash by four times.

Daniel Gregory (5):
  config/riscv: add flag for using Zbc extension
  hash: implement crc using riscv carryless multiply
  net: implement crc using riscv carryless multiply
  examples/l3fwd: use accelerated crc on riscv
  ipfrag: use accelerated crc on riscv

 MAINTAINERS                    |   2 +
 app/test/test_crc.c            |   9 ++
 app/test/test_hash.c           |   7 ++
 config/riscv/meson.build       |   7 ++
 examples/l3fwd/l3fwd_em.c      |   2 +-
 lib/hash/meson.build           |   1 +
 lib/hash/rte_crc_riscv64.h     |  89 +++++++++++++++
 lib/hash/rte_hash_crc.c        |  12 +-
 lib/hash/rte_hash_crc.h        |   6 +-
 lib/ip_frag/ip_frag_internal.c |   6 +-
 lib/net/meson.build            |   4 +
 lib/net/net_crc.h              |  11 ++
 lib/net/net_crc_zbc.c          | 202 +++++++++++++++++++++++++++++++++
 lib/net/rte_net_crc.c          |  35 ++++++
 lib/net/rte_net_crc.h          |   2 +
 15 files changed, 389 insertions(+), 6 deletions(-)
 create mode 100644 lib/hash/rte_crc_riscv64.h
 create mode 100644 lib/net/net_crc_zbc.c