reflect: make Value an opaque struct
Making Value opaque means we can drop the interface kludges
in favor of a significantly simpler and faster representation.
v.Kind() will be a prime candidate for inlining too.
On a Thinkpad X201s using -benchtime 10:
benchmark old ns/op new ns/op delta
json.BenchmarkCodeEncoder
284391780 157415960 -44.65%
json.BenchmarkCodeMarshal
286979140 158992020 -44.60%
json.BenchmarkCodeDecoder
717175800 388288220 -45.86%
json.BenchmarkCodeUnmarshal
734470500 404548520 -44.92%
json.BenchmarkCodeUnmarshalReuse
707172280 385258720 -45.52%
json.BenchmarkSkipValue
24630036 18557062 -24.66%
benchmark old MB/s new MB/s speedup
json.BenchmarkCodeEncoder 6.82 12.33 1.81x
json.BenchmarkCodeMarshal 6.76 12.20 1.80x
json.BenchmarkCodeDecoder 2.71 5.00 1.85x
json.BenchmarkCodeUnmarshal 2.64 4.80 1.82x
json.BenchmarkCodeUnmarshalReuse 2.74 5.04 1.84x
json.BenchmarkSkipValue 77.92 103.42 1.33x
I cannot explain why BenchmarkSkipValue gets faster.
Maybe it is one of those code alignment things.
R=iant, r, gri, r
CC=golang-dev
https://golang.org/cl/
5373101