From ed8f207940c8787d344664a43071b235e2ce5c68 Mon Sep 17 00:00:00 2001 From: Kevin Burke Date: Sun, 26 Jun 2016 09:47:43 -0700 Subject: [PATCH] encoding/json: Use a lookup table for safe characters MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The previous check for characters inside of a JSON string that needed to be escaped performed seven different boolean comparisons before determining that a ASCII character did not need to be escaped. Most characters do not need to be escaped, so this check can be done in a more performant way. Use the same strategy as the unicode package for precomputing a range of characters that need to be escaped, then do a single lookup into a character array to determine whether the character needs escaping. On an AWS c4.large node: $ benchstat benchmarks/master-bench benchmarks/json-table-bench name old time/op new time/op delta CodeEncoder-2 19.0ms ± 0% 15.5ms ± 1% -18.16% (p=0.000 n=19+20) CodeMarshal-2 20.1ms ± 1% 16.8ms ± 2% -16.35% (p=0.000 n=20+21) CodeDecoder-2 49.3ms ± 1% 49.5ms ± 2% ~ (p=0.498 n=16+20) DecoderStream-2 416ns ± 0% 416ns ± 1% ~ (p=0.978 n=19+19) CodeUnmarshal-2 51.0ms ± 1% 50.9ms ± 1% ~ (p=0.490 n=19+17) CodeUnmarshalReuse-2 48.5ms ± 2% 48.5ms ± 2% ~ (p=0.989 n=20+19) UnmarshalString-2 541ns ± 1% 532ns ± 1% -1.75% (p=0.000 n=20+21) UnmarshalFloat64-2 485ns ± 1% 481ns ± 1% -0.92% (p=0.000 n=20+21) UnmarshalInt64-2 429ns ± 1% 427ns ± 1% -0.49% (p=0.000 n=19+20) Issue10335-2 631ns ± 1% 619ns ± 1% -1.84% (p=0.000 n=20+20) NumberIsValid-2 19.1ns ± 0% 19.1ns ± 0% ~ (all samples are equal) NumberIsValidRegexp-2 689ns ± 1% 690ns ± 0% ~ (p=0.150 n=20+20) SkipValue-2 14.0ms ± 0% 14.0ms ± 0% -0.05% (p=0.000 n=18+18) EncoderEncode-2 525ns ± 2% 512ns ± 1% -2.33% (p=0.000 n=20+18) name old speed new speed delta CodeEncoder-2 102MB/s ± 0% 125MB/s ± 1% +22.20% (p=0.000 n=19+20) CodeMarshal-2 96.6MB/s ± 1% 115.6MB/s ± 2% +19.56% (p=0.000 n=20+21) CodeDecoder-2 39.3MB/s ± 1% 39.2MB/s ± 2% ~ (p=0.464 n=16+20) CodeUnmarshal-2 38.1MB/s ± 1% 38.1MB/s ± 1% ~ (p=0.525 n=19+17) SkipValue-2 143MB/s ± 0% 143MB/s ± 0% +0.05% (p=0.000 n=18+18) I also took the data set reported in #5683 (browser telemetry data from Mozilla), added named structs for the data set, and turned it into a proper benchmark: https://github.com/kevinburke/jsonbench/blob/master/go/bench_test.go The results from that test are similarly encouraging. On a 64-bit Mac: $ benchstat benchmarks/master-benchmark benchmarks/json-table-benchmark name old time/op new time/op delta CodeMarshal-4 1.19ms ± 2% 1.08ms ± 2% -9.33% (p=0.000 n=21+17) Unmarshal-4 3.09ms ± 3% 3.06ms ± 1% -0.83% (p=0.027 n=22+17) UnmarshalReuse-4 3.04ms ± 1% 3.04ms ± 1% ~ (p=0.169 n=20+15) name old speed new speed delta CodeMarshal-4 80.3MB/s ± 1% 88.5MB/s ± 1% +10.29% (p=0.000 n=21+17) Unmarshal-4 31.0MB/s ± 2% 31.2MB/s ± 1% +0.83% (p=0.025 n=22+17) On the c4.large: $ benchstat benchmarks/master-bench benchmarks/json-table-bench name old time/op new time/op delta CodeMarshal-2 1.10ms ± 1% 0.98ms ± 1% -10.12% (p=0.000 n=20+54) Unmarshal-2 2.82ms ± 1% 2.79ms ± 0% -1.09% (p=0.000 n=20+51) UnmarshalReuse-2 2.80ms ± 0% 2.77ms ± 0% -1.03% (p=0.000 n=20+52) name old speed new speed delta CodeMarshal-2 87.3MB/s ± 1% 97.1MB/s ± 1% +11.27% (p=0.000 n=20+54) Unmarshal-2 33.9MB/s ± 1% 34.2MB/s ± 0% +1.10% (p=0.000 n=20+51) For what it's worth, I tried other heuristics - short circuiting the conditional for common ASCII characters, for example: if (b >= 63 && b != 92) || (b >= 39 && b <= 59) || (rest of the conditional) This offered a speedup around 7-9%, not as large as the submitted change. Change-Id: Idcf88f7b93bfcd1164cdd6a585160b7e407a0d9b Reviewed-on: https://go-review.googlesource.com/24466 Reviewed-by: Joe Tsai Run-TryBot: Joe Tsai TryBot-Result: Gobot Gobot --- src/encoding/json/encode.go | 6 +- src/encoding/json/tables.go | 218 ++++++++++++++++++++++++++++++++++++ 2 files changed, 220 insertions(+), 4 deletions(-) create mode 100644 src/encoding/json/tables.go diff --git a/src/encoding/json/encode.go b/src/encoding/json/encode.go index 6bb6de8f07..6ef4e45c1e 100644 --- a/src/encoding/json/encode.go +++ b/src/encoding/json/encode.go @@ -850,8 +850,7 @@ func (e *encodeState) string(s string, escapeHTML bool) int { start := 0 for i := 0; i < len(s); { if b := s[i]; b < utf8.RuneSelf { - if 0x20 <= b && b != '\\' && b != '"' && - (!escapeHTML || b != '<' && b != '>' && b != '&') { + if htmlSafeSet[b] || (!escapeHTML && safeSet[b]) { i++ continue } @@ -928,8 +927,7 @@ func (e *encodeState) stringBytes(s []byte, escapeHTML bool) int { start := 0 for i := 0; i < len(s); { if b := s[i]; b < utf8.RuneSelf { - if 0x20 <= b && b != '\\' && b != '"' && - (!escapeHTML || b != '<' && b != '>' && b != '&') { + if htmlSafeSet[b] || (!escapeHTML && safeSet[b]) { i++ continue } diff --git a/src/encoding/json/tables.go b/src/encoding/json/tables.go new file mode 100644 index 0000000000..10acdc18c6 --- /dev/null +++ b/src/encoding/json/tables.go @@ -0,0 +1,218 @@ +// Copyright 2016 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package json + +import "unicode/utf8" + +// safeSet holds the value true if the ASCII character with the given array +// position can be represented inside a JSON string without any further +// escaping. +// +// All values are true except for the ASCII control characters (0-31), the +// double quote ("), and the backslash character ("\"). +var safeSet = [utf8.RuneSelf]bool{ + ' ': true, + '!': true, + '"': false, + '#': true, + '$': true, + '%': true, + '&': true, + '\'': true, + '(': true, + ')': true, + '*': true, + '+': true, + ',': true, + '-': true, + '.': true, + '/': true, + '0': true, + '1': true, + '2': true, + '3': true, + '4': true, + '5': true, + '6': true, + '7': true, + '8': true, + '9': true, + ':': true, + ';': true, + '<': true, + '=': true, + '>': true, + '?': true, + '@': true, + 'A': true, + 'B': true, + 'C': true, + 'D': true, + 'E': true, + 'F': true, + 'G': true, + 'H': true, + 'I': true, + 'J': true, + 'K': true, + 'L': true, + 'M': true, + 'N': true, + 'O': true, + 'P': true, + 'Q': true, + 'R': true, + 'S': true, + 'T': true, + 'U': true, + 'V': true, + 'W': true, + 'X': true, + 'Y': true, + 'Z': true, + '[': true, + '\\': false, + ']': true, + '^': true, + '_': true, + '`': true, + 'a': true, + 'b': true, + 'c': true, + 'd': true, + 'e': true, + 'f': true, + 'g': true, + 'h': true, + 'i': true, + 'j': true, + 'k': true, + 'l': true, + 'm': true, + 'n': true, + 'o': true, + 'p': true, + 'q': true, + 'r': true, + 's': true, + 't': true, + 'u': true, + 'v': true, + 'w': true, + 'x': true, + 'y': true, + 'z': true, + '{': true, + '|': true, + '}': true, + '~': true, + '\u007f': true, +} + +// htmlSafeSet holds the value true if the ASCII character with the given +// array position can be safely represented inside a JSON string, embedded +// inside of HTML