The RISC-V Zbc extension adds instructions for carry-less multiplication we can use to implement CRC in hardware. This patch set 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/ Whether these new implementations are enabled is controlled by new build-time and run-time detection of the RISC-V extensions present in the compiler and on the target system. 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. I have also run the hash_functions_autotest benchmark in dpdk_test, which measures the performance of the lib/hash implementation on small buffers, getting the following times: | Key Length | Time (ticks/op) | | (bytes) | Table | Hardware | |------------|----------|----------| | 1 | 0.47 | 0.85 | | 2 | 0.57 | 0.87 | | 4 | 0.99 | 0.88 | | 8 | 1.35 | 0.88 | | 9 | 1.20 | 1.09 | | 13 | 1.76 | 1.35 | | 16 | 1.87 | 1.02 | | 32 | 2.96 | 0.98 | | 37 | 3.35 | 1.45 | | 40 | 3.49 | 1.12 | | 48 | 4.02 | 1.25 | | 64 | 5.08 | 1.54 | v2: - replace compile flag with build-time (riscv extension macros) and run-time detection (linux hwprobe syscall) (Stephen Hemminger) - add qemu target that supports zbc (Stanislaw Kardach) - fix spelling error in commit message - fix a bug in the net/ implementation that would cause segfaults on small unaligned buffers - refactor net/ implemementation to move variable declarations to top of functions - enable the optimisation in a couple other places optimised crc is preferred to jhash - l3fwd-power - cuckoo-hash Daniel Gregory (9): config/riscv: detect presence of Zbc extension hash: implement crc using riscv carryless multiply net: implement crc using riscv carryless multiply config/riscv: add qemu crossbuild target examples/l3fwd: use accelerated crc on riscv ipfrag: use accelerated crc on riscv examples/l3fwd-power: use accelerated crc on riscv hash/cuckoo: use accelerated crc on riscv member: use accelerated crc on riscv MAINTAINERS | 2 + app/test/test_crc.c | 9 + app/test/test_hash.c | 7 + config/riscv/meson.build | 44 +++- config/riscv/riscv64_qemu_linux_gcc | 17 ++ .../linux_gsg/cross_build_dpdk_for_riscv.rst | 5 + examples/l3fwd-power/main.c | 2 +- examples/l3fwd/l3fwd_em.c | 2 +- lib/eal/riscv/include/rte_cpuflags.h | 2 + lib/eal/riscv/rte_cpuflags.c | 112 +++++++--- lib/hash/meson.build | 1 + lib/hash/rte_crc_riscv64.h | 89 ++++++++ lib/hash/rte_cuckoo_hash.c | 3 + lib/hash/rte_hash_crc.c | 13 +- lib/hash/rte_hash_crc.h | 6 +- lib/ip_frag/ip_frag_internal.c | 6 +- lib/member/rte_member.h | 2 +- lib/net/meson.build | 4 + lib/net/net_crc.h | 11 + lib/net/net_crc_zbc.c | 191 ++++++++++++++++++ lib/net/rte_net_crc.c | 40 ++++ lib/net/rte_net_crc.h | 2 + 22 files changed, 529 insertions(+), 41 deletions(-) create mode 100644 config/riscv/riscv64_qemu_linux_gcc create mode 100644 lib/hash/rte_crc_riscv64.h create mode 100644 lib/net/net_crc_zbc.c -- 2.39.2
