0c819b654f
This commit improves the processing of the final few bytes in castagnoliSSE42: instead of processing one byte at a time, we use all versions of the CRC32 instruction to process 4 bytes, then 2, then 1. The difference is only noticeable for small "odd" sized buffers. We do the similar improvement for processing the first few bytes in the case of unaligned buffer. Fixing the test which was not actually verifying the results for misaligned buffers (WriteString was creating an internal copy which was aligned). Adding benchmarks for length 15 (aligned and misaligned), results below. name old time/op new time/op delta CastagnoliCrc15B-4 25.1ns ± 0% 22.1ns ± 1% -12.14% CastagnoliCrc15BMisaligned-4 25.2ns ± 0% 22.9ns ± 1% -9.03% CastagnoliCrc40B-4 23.1ns ± 0% 23.4ns ± 0% +1.08% CastagnoliCrc1KB-4 127ns ± 0% 128ns ± 0% +1.18% CastagnoliCrc4KB-4 462ns ± 0% 464ns ± 0% ~ CastagnoliCrc32KB-4 3.58µs ± 0% 3.60µs ± 0% +0.58% name old speed new speed delta CastagnoliCrc15B-4 597MB/s ± 0% 679MB/s ± 1% +13.77% CastagnoliCrc15BMisaligned-4 596MB/s ± 0% 655MB/s ± 1% +9.94% CastagnoliCrc40B-4 1.73GB/s ± 0% 1.71GB/s ± 0% -1.14% CastagnoliCrc1KB-4 8.01GB/s ± 0% 7.93GB/s ± 1% -1.06% CastagnoliCrc4KB-4 8.86GB/s ± 0% 8.83GB/s ± 0% ~ CastagnoliCrc32KB-4 9.14GB/s ± 0% 9.09GB/s ± 0% -0.58% Change-Id: I499e37af2241d28e3e5d522bbab836c1a718430a Reviewed-on: https://go-review.googlesource.com/24470 Reviewed-by: Keith Randall <khr@golang.org> |
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