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 -- 2.39.2
