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| author | Meng Zhuo <mzh@golangcn.org> | 2021-09-30 22:46:09 +0800 |
|---|---|---|
| committer | Meng Zhuo <mzh@golangcn.org> | 2021-10-07 14:01:52 +0000 |
| commit | ecb2f231fa41b581319505139f8d5ac779763bee (patch) | |
| tree | 9892a8ece179edd0a1a88273e271255d18295b62 /src/runtime/malloc.go | |
| parent | 6f74ed06c5b0e1d69fb70e89f31f002f18554c79 (diff) | |
| download | go-ecb2f231fa41b581319505139f8d5ac779763bee.tar.xz | |
runtime,sync: using fastrandn instead of modulo reduction
fastrandn is ~50% faster than fastrand() % n.
`ack -v 'fastrand\(\)\s?\%'` finds all modulo on fastrand()
name old time/op new time/op delta
Fastrandn/2 2.86ns ± 0% 1.59ns ± 0% -44.35% (p=0.000 n=9+10)
Fastrandn/3 2.87ns ± 1% 1.59ns ± 0% -44.41% (p=0.000 n=10+9)
Fastrandn/4 2.87ns ± 1% 1.58ns ± 1% -45.10% (p=0.000 n=10+10)
Fastrandn/5 2.86ns ± 1% 1.58ns ± 1% -44.84% (p=0.000 n=10+10)
Change-Id: Ic91f5ca9b9e3b65127bc34792b62fd64fbd13b5c
Reviewed-on: https://go-review.googlesource.com/c/go/+/353269
Trust: Meng Zhuo <mzh@golangcn.org>
Run-TryBot: Meng Zhuo <mzh@golangcn.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Diffstat (limited to 'src/runtime/malloc.go')
| -rw-r--r-- | src/runtime/malloc.go | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go index 7affe244a2..c389cb1e45 100644 --- a/src/runtime/malloc.go +++ b/src/runtime/malloc.go @@ -1301,7 +1301,7 @@ func fastexprand(mean int) int32 { // x = -log_e(q) * mean // x = log_2(q) * (-log_e(2)) * mean ; Using log_2 for efficiency const randomBitCount = 26 - q := fastrand()%(1<<randomBitCount) + 1 + q := fastrandn(1<<randomBitCount) + 1 qlog := fastlog2(float64(q)) - randomBitCount if qlog > 0 { qlog = 0 @@ -1319,7 +1319,7 @@ func nextSampleNoFP() uintptr { rate = 0x3fffffff } if rate != 0 { - return uintptr(fastrand() % uint32(2*rate)) + return uintptr(fastrandn(uint32(2 * rate))) } return 0 } |