Microbenchmark of the checksum function vs C version at different buffer sizes:
Results (GB/s, higher is better; speedup = VSX / scalar):
64B: VSX 4.61 vs scalar 5.91 -> 0.78x (VSX slower for tiny buffers)
256B: VSX 10.91 vs scalar 7.57 -> 1.44x
1500B: VSX 13.88 vs scalar 6.89 -> 2.02x
16KB: VSX 14.53 vs scalar 6.96 -> 2.09x
64KB: VSX 15.15 vs scalar 6.85 -> 2.21x
On Friday, February 6th, 2026 at 3:17 PM, Laurent Vivier
On Thu, 05 Feb 2026 06:14:40 +0000, jfiusdq jfiusdq@proton.me wrote:
Tested with podman on Debian 13 for a while and works ok. It's difficult to run all the tests on POWER but 505-networking-pasta.bats test suite passes. --- checksum.c | 110 +++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 107 insertions(+), 3 deletions(-)
diff --git a/checksum.c b/checksum.c index 0c3837c..828f9ec 100644 --- a/checksum.c +++ b/checksum.c @@ -281,7 +281,7 @@ void csum_icmp6(struct icmp6hdr *icmp6hr, icmp6hr->icmp6_cksum = csum(payload, dlen, psum); }
-#ifdef AVX2 +#if defined(AVX2) #include
/** @@ -479,7 +479,111 @@ uint32_t csum_unfolded(const void *buf, size_t len, uint32_t init)
return init; } -#else /* AVX2 / +#elif defined(POWER9_VECTOR) || defined(POWER8_VECTOR) +#include
+ +/* + * csum_vsx() - Compute 32-bit checksum using VSX SIMD instructions + * @buf: Input buffer + * @len: Input length + * @init: Initial 32-bit checksum, 0 for no pre-computed checksum + * + * Return: 32-bit checksum, not complemented, not folded + / +/ NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) / +attribute((optimize("-fno-strict-aliasing"))) / See csum_16b() */ +static uint32_t csum_vsx(const void buf, size_t len, uint32_t init) +{ + const uint8_t p = buf; + vector unsigned int sum_even = vec_splat_u32(0); + vector unsigned int sum_odd = vec_splat_u32(0); + const vector unsigned short ones = vec_splat_u16(1); + uint64_t sum64 = init; + +#ifdef POWER9_VECTOR + while (len >= 64) { + vector unsigned char v0b = vec_vsx_ld(0, p); + vector unsigned char v1b = vec_vsx_ld(16, p); + vector unsigned char v2b = vec_vsx_ld(32, p); + vector unsigned char v3b = vec_vsx_ld(48, p); + vector unsigned short v0 = (vector unsigned short)v0b; + vector unsigned short v1 = (vector unsigned short)v1b; + vector unsigned short v2 = (vector unsigned short)v2b; + vector unsigned short v3 = (vector unsigned short)v3b; + + sum_even = vec_add(sum_even, vec_mule(v0, ones)); + sum_odd = vec_add(sum_odd, vec_mulo(v0, ones)); + sum_even = vec_add(sum_even, vec_mule(v1, ones)); + sum_odd = vec_add(sum_odd, vec_mulo(v1, ones)); + sum_even = vec_add(sum_even, vec_mule(v2, ones)); + sum_odd = vec_add(sum_odd, vec_mulo(v2, ones)); + sum_even = vec_add(sum_even, vec_mule(v3, ones)); + sum_odd = vec_add(sum_odd, vec_mulo(v3, ones)); + + p += 64; + len -= 64; + } +#endif + + while (len >= 32) { + vector unsigned char v0b = vec_vsx_ld(0, p); + vector unsigned char v1b = vec_vsx_ld(16, p); + vector unsigned short v0 = (vector unsigned short)v0b; + vector unsigned short v1 = (vector unsigned short)v1b; + + sum_even = vec_add(sum_even, vec_mule(v0, ones)); + sum_odd = vec_add(sum_odd, vec_mulo(v0, ones)); + sum_even = vec_add(sum_even, vec_mule(v1, ones)); + sum_odd = vec_add(sum_odd, vec_mulo(v1, ones)); + + p += 32; + len -= 32; + } + + while (len >= 16) { + vector unsigned char v0b = vec_vsx_ld(0, p); + vector unsigned short v0 = (vector unsigned short)v0b; + + sum_even = vec_add(sum_even, vec_mule(v0, ones)); + sum_odd = vec_add(sum_odd, vec_mulo(v0, ones)); + + p += 16; + len -= 16; + } + + { + vector unsigned int sum32 = vec_add(sum_even, sum_odd); + uint32_t partial[4] attribute((aligned(16))); + + vec_st(sum32, 0, partial); + sum64 += (uint64_t)partial[0] + partial[1] + + partial[2] + partial[3]; + } + + sum64 += sum_16b(p, len); + + sum64 = (sum64 >> 32) + (sum64 & 0xffffffff); + sum64 += sum64 >> 32; + + return (uint32_t)sum64; +} + +/ + * csum_unfolded() - Calculate the unfolded checksum of a data buffer. + * + * @buf: Input buffer + * @len: Input length + * @init: Initial 32-bit checksum, 0 for no pre-computed checksum + * + * Return: 32-bit unfolded checksum + / +/ NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) / +attribute((optimize("-fno-strict-aliasing"))) / See csum_16b() / +uint32_t csum_unfolded(const void buf, size_t len, uint32_t init) +{ + return csum_vsx(buf, len, init); +} +#else / !AVX2 && !POWER9_VECTOR && !POWER8_VECTOR / / * csum_unfolded() - Calculate the unfolded checksum of a data buffer. * @@ -495,7 +599,7 @@ uint32_t csum_unfolded(const void buf, size_t len, uint32_t init) { return sum_16b(buf, len) + init; } -#endif / !AVX2 / +#endif / !AVX2 && !POWER9_VECTOR && !POWER8_VECTOR */
/** * csum_iov_tail() - Calculate unfolded checksum for the tail of an IO vector -- 2.52.0
Reviewed-by: Laurent Vivier lvivier@redhat.com