Re: [PATCH 0/4] RISC-V CRC optimizations

["Björn Töpel" <bjorn@kernel.org>]

Eric!

Eric Biggers <ebiggers@kernel.org> writes:

> On Sun, Feb 16, 2025 at 02:55:26PM -0800, Eric Biggers wrote:
>> This patchset is a replacement for
>> "[PATCH v4] riscv: Optimize crct10dif with Zbc extension"
>> (https://lore.kernel.org/r/20250211071101.181652-1-zhihang.shao.iscas@gmail.com/).
>> It adopts the approach that I'm taking for x86 where code is shared
>> among CRC variants.  It replaces the existing Zbc optimized CRC32
>> functions, then adds Zbc optimized CRC-T10DIF and CRC64 functions.
>> 
>> This new code should be significantly faster than the current Zbc
>> optimized CRC32 code and the previously proposed CRC-T10DIF code.  It
>> uses "folding" instead of just Barrett reduction, and it also implements
>> Barrett reduction more efficiently.
>> 
>> This applies to crc-next at
>> https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=crc-next.
>> It depends on other patches that are queued there for 6.15, so I plan to
>> take it through there if there are no objections.
>> 
>> Tested with crc_kunit in QEMU (set CONFIG_CRC_KUNIT_TEST=y and
>> CONFIG_CRC_BENCHMARK=y), both 32-bit and 64-bit.  I don't have real Zbc
>> capable hardware to benchmark this on, but the new code should work very
>> well; similar optimizations work very well on other architectures.
>
> Any feedback on this series from the RISC-V side?

I have not reviewed your series, but I did a testrun the Milk-V Jupiter
which sports a Spacemit K1 that has Zbc.

I based the run on commit 1973160c90d7 ("Merge tag
'gpio-fixes-for-v6.14-rc5' of
git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux"), plus your
crc-next branch (commit a0bd462f3a13 ("x86/crc: add ANNOTATE_NOENDBR to
suppress objtool warnings")) merged:

  | --- base1.txt	2025-03-02 18:31:16.169438876 +0000
  | +++ eric.txt	2025-03-02 18:35:58.683017223 +0000
  | @@ -11,7 +11,7 @@
  |      # crc16_benchmark: len=127: 153 MB/s
  |      # crc16_benchmark: len=128: 153 MB/s
  |      # crc16_benchmark: len=200: 153 MB/s
  | -    # crc16_benchmark: len=256: 153 MB/s
  | +    # crc16_benchmark: len=256: 154 MB/s
  |      # crc16_benchmark: len=511: 154 MB/s
  |      # crc16_benchmark: len=512: 154 MB/s
  |      # crc16_benchmark: len=1024: 155 MB/s
  | @@ -20,94 +20,94 @@
  |      # crc16_benchmark: len=16384: 155 MB/s
  |      ok 2 crc16_benchmark
  |      ok 3 crc_t10dif_test
  | -    # crc_t10dif_benchmark: len=1: 48 MB/s
  | -    # crc_t10dif_benchmark: len=16: 125 MB/s
  | -    # crc_t10dif_benchmark: len=64: 136 MB/s
  | -    # crc_t10dif_benchmark: len=127: 138 MB/s
  | -    # crc_t10dif_benchmark: len=128: 138 MB/s
  | -    # crc_t10dif_benchmark: len=200: 138 MB/s
  | -    # crc_t10dif_benchmark: len=256: 138 MB/s
  | -    # crc_t10dif_benchmark: len=511: 139 MB/s
  | -    # crc_t10dif_benchmark: len=512: 139 MB/s
  | -    # crc_t10dif_benchmark: len=1024: 139 MB/s
  | -    # crc_t10dif_benchmark: len=3173: 140 MB/s
  | -    # crc_t10dif_benchmark: len=4096: 140 MB/s
  | -    # crc_t10dif_benchmark: len=16384: 140 MB/s
  | +    # crc_t10dif_benchmark: len=1: 28 MB/s
  | +    # crc_t10dif_benchmark: len=16: 236 MB/s
  | +    # crc_t10dif_benchmark: len=64: 450 MB/s
  | +    # crc_t10dif_benchmark: len=127: 480 MB/s
  | +    # crc_t10dif_benchmark: len=128: 540 MB/s
  | +    # crc_t10dif_benchmark: len=200: 559 MB/s
  | +    # crc_t10dif_benchmark: len=256: 600 MB/s
  | +    # crc_t10dif_benchmark: len=511: 613 MB/s
  | +    # crc_t10dif_benchmark: len=512: 635 MB/s
  | +    # crc_t10dif_benchmark: len=1024: 654 MB/s
  | +    # crc_t10dif_benchmark: len=3173: 665 MB/s
  | +    # crc_t10dif_benchmark: len=4096: 669 MB/s
  | +    # crc_t10dif_benchmark: len=16384: 673 MB/s
  |      ok 4 crc_t10dif_benchmark
  |      ok 5 crc32_le_test
  |      # crc32_le_benchmark: len=1: 31 MB/s
  | -    # crc32_le_benchmark: len=16: 456 MB/s
  | -    # crc32_le_benchmark: len=64: 682 MB/s
  | -    # crc32_le_benchmark: len=127: 620 MB/s
  | -    # crc32_le_benchmark: len=128: 744 MB/s
  | -    # crc32_le_benchmark: len=200: 768 MB/s
  | -    # crc32_le_benchmark: len=256: 777 MB/s
  | -    # crc32_le_benchmark: len=511: 758 MB/s
  | -    # crc32_le_benchmark: len=512: 798 MB/s
  | -    # crc32_le_benchmark: len=1024: 807 MB/s
  | -    # crc32_le_benchmark: len=3173: 807 MB/s
  | -    # crc32_le_benchmark: len=4096: 814 MB/s
  | -    # crc32_le_benchmark: len=16384: 816 MB/s
  | +    # crc32_le_benchmark: len=16: 439 MB/s
  | +    # crc32_le_benchmark: len=64: 1209 MB/s
  | +    # crc32_le_benchmark: len=127: 1067 MB/s
  | +    # crc32_le_benchmark: len=128: 1616 MB/s
  | +    # crc32_le_benchmark: len=200: 1739 MB/s
  | +    # crc32_le_benchmark: len=256: 1951 MB/s
  | +    # crc32_le_benchmark: len=511: 1855 MB/s
  | +    # crc32_le_benchmark: len=512: 2174 MB/s
  | +    # crc32_le_benchmark: len=1024: 2301 MB/s
  | +    # crc32_le_benchmark: len=3173: 2347 MB/s
  | +    # crc32_le_benchmark: len=4096: 2407 MB/s
  | +    # crc32_le_benchmark: len=16384: 2440 MB/s
  |      ok 6 crc32_le_benchmark
  |      ok 7 crc32_be_test
  | -    # crc32_be_benchmark: len=1: 27 MB/s
  | -    # crc32_be_benchmark: len=16: 258 MB/s
  | -    # crc32_be_benchmark: len=64: 388 MB/s
  | -    # crc32_be_benchmark: len=127: 402 MB/s
  | -    # crc32_be_benchmark: len=128: 424 MB/s
  | -    # crc32_be_benchmark: len=200: 438 MB/s
  | -    # crc32_be_benchmark: len=256: 444 MB/s
  | -    # crc32_be_benchmark: len=511: 449 MB/s
  | -    # crc32_be_benchmark: len=512: 455 MB/s
  | -    # crc32_be_benchmark: len=1024: 461 MB/s
  | -    # crc32_be_benchmark: len=3173: 463 MB/s
  | -    # crc32_be_benchmark: len=4096: 465 MB/s
  | -    # crc32_be_benchmark: len=16384: 466 MB/s
  | +    # crc32_be_benchmark: len=1: 25 MB/s
  | +    # crc32_be_benchmark: len=16: 251 MB/s
  | +    # crc32_be_benchmark: len=64: 458 MB/s
  | +    # crc32_be_benchmark: len=127: 496 MB/s
  | +    # crc32_be_benchmark: len=128: 547 MB/s
  | +    # crc32_be_benchmark: len=200: 569 MB/s
  | +    # crc32_be_benchmark: len=256: 605 MB/s
  | +    # crc32_be_benchmark: len=511: 621 MB/s
  | +    # crc32_be_benchmark: len=512: 637 MB/s
  | +    # crc32_be_benchmark: len=1024: 657 MB/s
  | +    # crc32_be_benchmark: len=3173: 668 MB/s
  | +    # crc32_be_benchmark: len=4096: 671 MB/s
  | +    # crc32_be_benchmark: len=16384: 674 MB/s
  |      ok 8 crc32_be_benchmark
  |      ok 9 crc32c_test
  |      # crc32c_benchmark: len=1: 31 MB/s
  | -    # crc32c_benchmark: len=16: 457 MB/s
  | -    # crc32c_benchmark: len=64: 682 MB/s
  | -    # crc32c_benchmark: len=127: 620 MB/s
  | -    # crc32c_benchmark: len=128: 744 MB/s
  | -    # crc32c_benchmark: len=200: 769 MB/s
  | -    # crc32c_benchmark: len=256: 779 MB/s
  | -    # crc32c_benchmark: len=511: 758 MB/s
  | -    # crc32c_benchmark: len=512: 797 MB/s
  | -    # crc32c_benchmark: len=1024: 807 MB/s
  | -    # crc32c_benchmark: len=3173: 806 MB/s
  | -    # crc32c_benchmark: len=4096: 813 MB/s
  | -    # crc32c_benchmark: len=16384: 816 MB/s
  | +    # crc32c_benchmark: len=16: 446 MB/s
  | +    # crc32c_benchmark: len=64: 1188 MB/s
  | +    # crc32c_benchmark: len=127: 1066 MB/s
  | +    # crc32c_benchmark: len=128: 1600 MB/s
  | +    # crc32c_benchmark: len=200: 1727 MB/s
  | +    # crc32c_benchmark: len=256: 1941 MB/s
  | +    # crc32c_benchmark: len=511: 1854 MB/s
  | +    # crc32c_benchmark: len=512: 2164 MB/s
  | +    # crc32c_benchmark: len=1024: 2300 MB/s
  | +    # crc32c_benchmark: len=3173: 2345 MB/s
  | +    # crc32c_benchmark: len=4096: 2402 MB/s
  | +    # crc32c_benchmark: len=16384: 2437 MB/s
  |      ok 10 crc32c_benchmark
  |      ok 11 crc64_be_test
  | -    # crc64_be_benchmark: len=1: 64 MB/s
  | -    # crc64_be_benchmark: len=16: 144 MB/s
  | -    # crc64_be_benchmark: len=64: 154 MB/s
  | -    # crc64_be_benchmark: len=127: 156 MB/s
  | -    # crc64_be_benchmark: len=128: 156 MB/s
  | -    # crc64_be_benchmark: len=200: 156 MB/s
  | -    # crc64_be_benchmark: len=256: 156 MB/s
  | -    # crc64_be_benchmark: len=511: 157 MB/s
  | -    # crc64_be_benchmark: len=512: 157 MB/s
  | -    # crc64_be_benchmark: len=1024: 157 MB/s
  | -    # crc64_be_benchmark: len=3173: 158 MB/s
  | -    # crc64_be_benchmark: len=4096: 158 MB/s
  | -    # crc64_be_benchmark: len=16384: 158 MB/s
  | +    # crc64_be_benchmark: len=1: 29 MB/s
  | +    # crc64_be_benchmark: len=16: 264 MB/s
  | +    # crc64_be_benchmark: len=64: 476 MB/s
  | +    # crc64_be_benchmark: len=127: 499 MB/s
  | +    # crc64_be_benchmark: len=128: 558 MB/s
  | +    # crc64_be_benchmark: len=200: 576 MB/s
  | +    # crc64_be_benchmark: len=256: 611 MB/s
  | +    # crc64_be_benchmark: len=511: 621 MB/s
  | +    # crc64_be_benchmark: len=512: 638 MB/s
  | +    # crc64_be_benchmark: len=1024: 659 MB/s
  | +    # crc64_be_benchmark: len=3173: 667 MB/s
  | +    # crc64_be_benchmark: len=4096: 671 MB/s
  | +    # crc64_be_benchmark: len=16384: 674 MB/s
  |      ok 12 crc64_be_benchmark
  |      ok 13 crc64_nvme_test
  | -    # crc64_nvme_benchmark: len=1: 64 MB/s
  | -    # crc64_nvme_benchmark: len=16: 144 MB/s
  | -    # crc64_nvme_benchmark: len=64: 154 MB/s
  | -    # crc64_nvme_benchmark: len=127: 156 MB/s
  | -    # crc64_nvme_benchmark: len=128: 156 MB/s
  | -    # crc64_nvme_benchmark: len=200: 156 MB/s
  | -    # crc64_nvme_benchmark: len=256: 156 MB/s
  | -    # crc64_nvme_benchmark: len=511: 157 MB/s
  | -    # crc64_nvme_benchmark: len=512: 157 MB/s
  | -    # crc64_nvme_benchmark: len=1024: 157 MB/s
  | -    # crc64_nvme_benchmark: len=3173: 158 MB/s
  | -    # crc64_nvme_benchmark: len=4096: 158 MB/s
  | -    # crc64_nvme_benchmark: len=16384: 158 MB/s
  | +    # crc64_nvme_benchmark: len=1: 36 MB/s
  | +    # crc64_nvme_benchmark: len=16: 479 MB/s
  | +    # crc64_nvme_benchmark: len=64: 1340 MB/s
  | +    # crc64_nvme_benchmark: len=127: 1179 MB/s
  | +    # crc64_nvme_benchmark: len=128: 1766 MB/s
  | +    # crc64_nvme_benchmark: len=200: 1965 MB/s
  | +    # crc64_nvme_benchmark: len=256: 2201 MB/s
  | +    # crc64_nvme_benchmark: len=511: 2087 MB/s
  | +    # crc64_nvme_benchmark: len=512: 2464 MB/s
  | +    # crc64_nvme_benchmark: len=1024: 2331 MB/s
  | +    # crc64_nvme_benchmark: len=3173: 2673 MB/s
  | +    # crc64_nvme_benchmark: len=4096: 2745 MB/s
  | +    # crc64_nvme_benchmark: len=16384: 2782 MB/s
  |      ok 14 crc64_nvme_benchmark
  |  # crc: pass:14 fail:0 skip:0 total:14
  |  # Totals: pass:14 fail:0 skip:0 total:14

That's a significant speed up for this popular SoC, and it would be
great to get this series in for the next merge window! Thank you!

Tested-by: Björn Töpel <bjorn@rivosinc.com>


Björn

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