code review 7231058: encoding/json: improve performance of Unmarshal on prim...

encoding/json: improve performance of Unmarshal on primitive types

Attempt 2. The first fix was much faster but ignored syntax errors.

benchmark                      old ns/op    new ns/op    delta
BenchmarkCodeEncoder            74993543     72982390   -2.68%
BenchmarkCodeMarshal            77811181     75610637   -2.83%
BenchmarkCodeDecoder           213337123    190144982  -10.87%
BenchmarkCodeUnmarshal         212180972    190394852  -10.27%
BenchmarkCodeUnmarshalReuse    202113428    182106660   -9.90%
BenchmarkUnmarshalString            1343          919  -31.57%
BenchmarkUnmarshalFloat64           1149          908  -20.97%
BenchmarkUnmarshalInt64              967          778  -19.54%
BenchmarkSkipValue              28851581     28414125   -1.52%

benchmark                       old MB/s     new MB/s  speedup
BenchmarkCodeEncoder               25.88        26.59    1.03x
BenchmarkCodeMarshal               24.94        25.66    1.03x
BenchmarkCodeDecoder                9.10        10.21    1.12x
BenchmarkCodeUnmarshal              9.15        10.19    1.11x
BenchmarkSkipValue                 69.05        70.11    1.02x

Fixes issue 3949.

[rick, 2013-01-29 22:55:39]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go

[rsc, 2013-01-30 17:23:01]

https://codereview.appspot.com/7231058/diff/4001/src/pkg/encoding/json/decode.go
File src/pkg/encoding/json/decode.go (right):

https://codereview.appspot.com/7231058/diff/4001/src/pkg/encoding/json/decode...
src/pkg/encoding/json/decode.go:78: d := new(decodeState).init(data)
Too much duplicated code. Please move all this (except the return statement) up
to the top of the function and then drop the duplication in the new chunk.

[rick, 2013-01-30 22:49:13]

PTAL

Benchmark numbers are within 2% of the previous patchset.

https://codereview.appspot.com/7231058/diff/4001/src/pkg/encoding/json/decode.go
File src/pkg/encoding/json/decode.go (right):

https://codereview.appspot.com/7231058/diff/4001/src/pkg/encoding/json/decode...
src/pkg/encoding/json/decode.go:78: d := new(decodeState).init(data)
On 2013/01/30 17:23:02, rsc wrote:
> Too much duplicated code. Please move all this (except the return statement)
up
> to the top of the function and then drop the duplication in the new chunk.

Done. Sorry, this was left over from my attempts to skip the checkValid call by
first doing some simple checks for "null", "true", "false", and obviously bad
strings and numbers. Turns out all that extra work didn't improve the speed.

[rsc, 2013-01-31 01:34:42]

https://codereview.appspot.com/7231058/diff/7001/src/pkg/encoding/json/decode.go
File src/pkg/encoding/json/decode.go (right):

https://codereview.appspot.com/7231058/diff/7001/src/pkg/encoding/json/decode...
src/pkg/encoding/json/decode.go:82: dp := new(decodeState).init(data)
There's already one above: let's use it.

d.init(data)
return d.unmarshal(v)

[rick, 2013-01-31 01:50:51]

PTAL

https://codereview.appspot.com/7231058/diff/7001/src/pkg/encoding/json/decode.go
File src/pkg/encoding/json/decode.go (right):

https://codereview.appspot.com/7231058/diff/7001/src/pkg/encoding/json/decode...
src/pkg/encoding/json/decode.go:82: dp := new(decodeState).init(data)
On 2013/01/31 01:34:43, rsc wrote:
> There's already one above: let's use it.
> 
> d.init(data)
> return d.unmarshal(v)

Done.

[rsc, 2013-01-31 01:52:01]

LGTM

[rsc, 2013-01-31 01:53:51]

*** Submitted as https://code.google.com/p/go/source/detail?r=de89928ea00f ***

encoding/json: improve performance of Unmarshal on primitive types

Attempt 2. The first fix was much faster but ignored syntax errors.

benchmark                      old ns/op    new ns/op    delta
BenchmarkCodeEncoder            74993543     72982390   -2.68%
BenchmarkCodeMarshal            77811181     75610637   -2.83%
BenchmarkCodeDecoder           213337123    190144982  -10.87%
BenchmarkCodeUnmarshal         212180972    190394852  -10.27%
BenchmarkCodeUnmarshalReuse    202113428    182106660   -9.90%
BenchmarkUnmarshalString            1343          919  -31.57%
BenchmarkUnmarshalFloat64           1149          908  -20.97%
BenchmarkUnmarshalInt64              967          778  -19.54%
BenchmarkSkipValue              28851581     28414125   -1.52%

benchmark                       old MB/s     new MB/s  speedup
BenchmarkCodeEncoder               25.88        26.59    1.03x
BenchmarkCodeMarshal               24.94        25.66    1.03x
BenchmarkCodeDecoder                9.10        10.21    1.12x
BenchmarkCodeUnmarshal              9.15        10.19    1.11x
BenchmarkSkipValue                 69.05        70.11    1.02x

Fixes issue 3949.

R=rsc
CC=golang-dev
https://codereview.appspot.com/7231058

Committer: Russ Cox <rsc@golang.org>