cyb70289 commented on PR #49756:
URL: https://github.com/apache/arrow/pull/49756#issuecomment-4310376121
> But it's impressive that SVE128 is always significantly better than NEON.
That's rather good news, given that most SVE implementations have 128-bit
vectors. @cyb70289
Interesting. It should not happen if both using equivalent simd operations.
I tested one case `BM_UnpackBool/{Neon,Sve128}Unaligned/1/32` on an Neoverse
N2 server, SVE shows double performance than Neon. But from profile result,
looks Neon code does not inline frequently called functions like `load_val_as`
and introduces high overhead.
**Benchmark**
```
BM_UnpackBool/NeonUnaligned/1/32 11.1 ns 11.0 ns
63329847 items_per_second=2.89667G/s
BM_UnpackBool/Sve128Unaligned/1/32 7.02 ns 7.02 ns
99743767 items_per_second=4.55851G/s
```
**Neon hotspot shows load_val_as is not inlined**
```
+ 45.20% arrow-bpacking- libarrow.so.2500.0.0 [.] void
arrow::internal::bpacking::unpack_width<1,
arrow::internal::bpacking::KernelNeon, bool>(unsigned char const
+ 31.03% arrow-bpacking- libarrow.so.2500.0.0 [.]
xsimd::batch<unsigned char, xsimd::neon64>
arrow::internal::bpacking::load_val_as<unsigned int, xsimd::neon64>(u
+ 7.08% arrow-bpacking- libarrow.so.2500.0.0 [.] void
arrow::internal::bpacking::MediumKernel<arrow::internal::bpacking::KernelTraits<bool,
1, xsimd::neon64>, ar
+ 6.38% arrow-bpacking- libarrow.so.2500.0.0 [.] void
arrow::internal::bpacking::MediumKernel<arrow::internal::bpacking::KernelTraits<bool,
1, xsimd::neon64>, ar
+ 2.63% arrow-bpacking- libarrow.so.2500.0.0 [.] void
arrow::internal::bpacking::unpack_neon<bool>(unsigned char const*, bool*,
arrow::internal::UnpackOptions co
+ 1.95% arrow-bpacking- arrow-bpacking-benchmark [.]
arrow::internal::(anonymous namespace)::BM_UnpackBool(benchmark::State&, bool,
void (*)(unsigned char const*, bo
+ 1.82% arrow-bpacking- libarrow.so.2500.0.0 [.]
xsimd::batch<unsigned char, xsimd::neon64>
arrow::internal::bpacking::load_val_as<unsigned int, xsimd::neon64>(u
+ 1.37% arrow-bpacking- libarrow.so.2500.0.0 [.] void
arrow::internal::bpacking::unpack_width<1,
arrow::internal::bpacking::KernelNeon, bool>(unsigned char const
```
**No such issue in sve128 code path**
```
+ 89.89% arrow-bpacking- libarrow.so.2500.0.0 [.] void
arrow::internal::bpacking::unpack_width<1, arrow::int◆
+ 4.18% arrow-bpacking- libarrow.so.2500.0.0 [.] void
arrow::internal::bpacking::unpack_sve128<bool>(unsign▒
+ 3.11% arrow-bpacking- arrow-bpacking-benchmark [.]
arrow::internal::(anonymous namespace)::BM_UnpackBool(benc▒
+ 1.47% arrow-bpacking- libarrow.so.2500.0.0 [.] void
arrow::internal::bpacking::unpack_width<1, arrow::int▒
```
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