From ddad9b618cce0ed91d66f0470ddb3e12cfd7eeac Mon Sep 17 00:00:00 2001 From: korzhao Date: Fri, 11 Aug 2023 17:20:36 +0800 Subject: [PATCH] encoding/json: avoid allocation when decoding number types MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In CL 345488, we optimized strconv.ParseXXX for []byte arguments. That allows immediate casting of a []byte to a string that does not escape to be copied on the stack. Performance: goos: darwin goarch: arm64 pkg: encoding/json old sec/op new sec/op delta CodeUnmarshal-10 3.019m ± 6% 2.865m ± 10% -5.10% (p=0.043 n=10) CodeUnmarshalReuse-10 2.528m ± 4% 2.274m ± 13% -10.03% (p=0.009 n=10) geomean 2.762m 2.553m -7.60% old B/s new B/s delta CodeUnmarshal-10 613.1Mi ± 5% 646.0Mi ± 9% +5.37% (p=0.043 n=10) CodeUnmarshalReuse-10 732.1Mi ± 4% 813.7Mi ± 12% +11.15% (p=0.009 n=10) geomean 669.9Mi 725.0Mi +8.22% old B/op new B/op delta CodeUnmarshal-10 2.782Mi ± 0% 1.918Mi ± 0% -31.04% (p=0.000 n=10) CodeUnmarshalReuse-10 1600.8Ki ± 0% 713.3Ki ± 0% -55.44% (p=0.000 n=10) geomean 2.085Mi 1.156Mi -44.57% old allocs/op new allocs/op delta CodeUnmarshal-10 91.31k ± 0% 39.99k ± 0% -56.20% (p=0.000 n=10) CodeUnmarshalReuse-10 76.58k ± 0% 25.23k ± 0% -67.06% (p=0.000 n=10) geomean 83.62k 31.76k -62.02% Change-Id: I208c57089040daee0f9d979d1df725e3acf34f81 Reviewed-on: https://go-review.googlesource.com/c/go/+/518277 Reviewed-by: Dmitri Shuralyov TryBot-Result: Gopher Robot Reviewed-by: Michael Knyszek Reviewed-by: Joseph Tsai Run-TryBot: Joseph Tsai Reviewed-by: Daniel Martí --- src/encoding/json/decode.go | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/src/encoding/json/decode.go b/src/encoding/json/decode.go index 858a2ed41a..72188a66f6 100644 --- a/src/encoding/json/decode.go +++ b/src/encoding/json/decode.go @@ -962,13 +962,12 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool } panic(phasePanicMsg) } - s := string(item) switch v.Kind() { default: if v.Kind() == reflect.String && v.Type() == numberType { // s must be a valid number, because it's // already been tokenized. - v.SetString(s) + v.SetString(string(item)) break } if fromQuoted { @@ -976,7 +975,7 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool } d.saveError(&UnmarshalTypeError{Value: "number", Type: v.Type(), Offset: int64(d.readIndex())}) case reflect.Interface: - n, err := d.convertNumber(s) + n, err := d.convertNumber(string(item)) if err != nil { d.saveError(err) break @@ -988,25 +987,25 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool v.Set(reflect.ValueOf(n)) case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64: - n, err := strconv.ParseInt(s, 10, 64) + n, err := strconv.ParseInt(string(item), 10, 64) if err != nil || v.OverflowInt(n) { - d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: v.Type(), Offset: int64(d.readIndex())}) + d.saveError(&UnmarshalTypeError{Value: "number " + string(item), Type: v.Type(), Offset: int64(d.readIndex())}) break } v.SetInt(n) case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr: - n, err := strconv.ParseUint(s, 10, 64) + n, err := strconv.ParseUint(string(item), 10, 64) if err != nil || v.OverflowUint(n) { - d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: v.Type(), Offset: int64(d.readIndex())}) + d.saveError(&UnmarshalTypeError{Value: "number " + string(item), Type: v.Type(), Offset: int64(d.readIndex())}) break } v.SetUint(n) case reflect.Float32, reflect.Float64: - n, err := strconv.ParseFloat(s, v.Type().Bits()) + n, err := strconv.ParseFloat(string(item), v.Type().Bits()) if err != nil || v.OverflowFloat(n) { - d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: v.Type(), Offset: int64(d.readIndex())}) + d.saveError(&UnmarshalTypeError{Value: "number " + string(item), Type: v.Type(), Offset: int64(d.readIndex())}) break } v.SetFloat(n)