From e53cc7ae931eeec0863d066d98972fc52fcd09f0 Mon Sep 17 00:00:00 2001 From: Ilya Tocar Date: Fri, 23 Mar 2018 15:45:03 -0500 Subject: runtime: avoid division in growslice MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add a special case for power-of-2 sized elements. We can replace div/mul with left/right shift and avoid expensive operation. growslice is hotter for short slices of small elements, such as int16, so add an int16 version for GrowSlice benchmark. name old time/op new time/op delta GrowSlice/Byte-6 61.3ns ± 3% 60.5ns ± 4% -1.33% (p=0.002 n=30+30) GrowSlice/Int16-6 94.0ns ± 4% 84.7ns ± 2% -9.82% (p=0.000 n=30+30) GrowSlice/Int-6 100ns ± 1% 99ns ± 1% -0.25% (p=0.032 n=29+28) GrowSlice/Ptr-6 197ns ± 2% 195ns ± 2% -0.94% (p=0.001 n=30+29) GrowSlice/Struct/24-6 168ns ± 1% 166ns ± 2% -1.09% (p=0.000 n=25+30) GrowSlice/Struct/32-6 187ns ± 2% 180ns ± 1% -3.59% (p=0.000 n=30+30) GrowSlice/Struct/40-6 241ns ± 2% 238ns ± 2% -1.41% (p=0.000 n=30+30) Change-Id: I31e8388d73fd9356e2dcc091d8d92eef3e3ccdbc Reviewed-on: https://go-review.googlesource.com/102279 Run-TryBot: Ilya Tocar TryBot-Result: Gobot Gobot Reviewed-by: Josh Bleecher Snyder --- src/runtime/slice_test.go | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'src/runtime/slice_test.go') diff --git a/src/runtime/slice_test.go b/src/runtime/slice_test.go index ef1e812c0d..46db071ebe 100644 --- a/src/runtime/slice_test.go +++ b/src/runtime/slice_test.go @@ -31,6 +31,12 @@ func BenchmarkGrowSlice(b *testing.B) { _ = append([]byte(nil), x...) } }) + b.Run("Int16", func(b *testing.B) { + x := make([]int16, 9) + for i := 0; i < b.N; i++ { + _ = append([]int16(nil), x...) + } + }) b.Run("Int", func(b *testing.B) { x := make([]int, 9) for i := 0; i < b.N; i++ { -- cgit v1.3-5-g9baa