parser.rl: parse_string implement a fast path

[casperisfine]

If we assume most string don't contain any escape sequence we can avoid a lot of costly operations when it holds true.

Before:

== Parsing activitypub.json (58160 bytes)
ruby 3.4.0dev (2024-11-06T07:59:09Z precompute-hash-wh.. 7943f98a8a) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
                json   884.000 i/100ms
                  oj   789.000 i/100ms
          Oj::Parser   943.000 i/100ms
           rapidjson   584.000 i/100ms
Calculating -------------------------------------
                json      8.897k (± 1.3%) i/s  (112.40 μs/i) -     45.084k in   5.068520s
                  oj      7.967k (± 1.5%) i/s  (125.52 μs/i) -     40.239k in   5.051985s
          Oj::Parser      9.564k (± 1.4%) i/s  (104.56 μs/i) -     48.093k in   5.029626s
           rapidjson      5.947k (± 1.4%) i/s  (168.16 μs/i) -     29.784k in   5.009437s

Comparison:
                json:     8896.5 i/s
          Oj::Parser:     9563.8 i/s - 1.08x  faster
                  oj:     7966.8 i/s - 1.12x  slower
           rapidjson:     5946.7 i/s - 1.50x  slower

== Parsing twitter.json (567916 bytes)
ruby 3.4.0dev (2024-11-06T07:59:09Z precompute-hash-wh.. 7943f98a8a) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
                json    83.000 i/100ms
                  oj    64.000 i/100ms
          Oj::Parser    77.000 i/100ms
           rapidjson    54.000 i/100ms
Calculating -------------------------------------
                json    823.083 (± 1.8%) i/s    (1.21 ms/i) -      4.150k in   5.043805s
                  oj    632.538 (± 1.4%) i/s    (1.58 ms/i) -      3.200k in   5.060073s
          Oj::Parser    769.122 (± 1.8%) i/s    (1.30 ms/i) -      3.850k in   5.007501s
           rapidjson    548.494 (± 1.5%) i/s    (1.82 ms/i) -      2.754k in   5.022153s

Comparison:
                json:      823.1 i/s
          Oj::Parser:      769.1 i/s - 1.07x  slower
                  oj:      632.5 i/s - 1.30x  slower
           rapidjson:      548.5 i/s - 1.50x  slower

== Parsing citm_catalog.json (1727030 bytes)
ruby 3.4.0dev (2024-11-06T07:59:09Z precompute-hash-wh.. 7943f98a8a) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
                json    41.000 i/100ms
                  oj    34.000 i/100ms
          Oj::Parser    45.000 i/100ms
           rapidjson    39.000 i/100ms
Calculating -------------------------------------
                json    427.162 (± 1.2%) i/s    (2.34 ms/i) -      2.173k in   5.087666s
                  oj    351.463 (± 2.8%) i/s    (2.85 ms/i) -      1.768k in   5.035149s
          Oj::Parser    461.849 (± 3.7%) i/s    (2.17 ms/i) -      2.340k in   5.074461s
           rapidjson    395.155 (± 1.8%) i/s    (2.53 ms/i) -      1.989k in   5.034927s

Comparison:
                json:      427.2 i/s
          Oj::Parser:      461.8 i/s - 1.08x  faster
           rapidjson:      395.2 i/s - 1.08x  slower
                  oj:      351.5 i/s - 1.22x  slower

After:

== Parsing activitypub.json (58160 bytes)
ruby 3.4.0dev (2024-11-06T07:59:09Z precompute-hash-wh.. 7943f98a8a) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
                json   953.000 i/100ms
                  oj   813.000 i/100ms
          Oj::Parser   956.000 i/100ms
           rapidjson   563.000 i/100ms
Calculating -------------------------------------
                json      9.525k (± 1.2%) i/s  (104.98 μs/i) -     47.650k in   5.003252s
                  oj      8.117k (± 0.5%) i/s  (123.20 μs/i) -     40.650k in   5.008283s
          Oj::Parser      9.590k (± 3.2%) i/s  (104.27 μs/i) -     48.756k in   5.089794s
           rapidjson      6.020k (± 0.9%) i/s  (166.10 μs/i) -     30.402k in   5.050155s

Comparison:
                json:     9525.3 i/s
          Oj::Parser:     9590.1 i/s - same-ish: difference falls within error
                  oj:     8116.7 i/s - 1.17x  slower
           rapidjson:     6020.5 i/s - 1.58x  slower

== Parsing twitter.json (567916 bytes)
ruby 3.4.0dev (2024-11-06T07:59:09Z precompute-hash-wh.. 7943f98a8a) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
                json    87.000 i/100ms
                  oj    64.000 i/100ms
          Oj::Parser    75.000 i/100ms
           rapidjson    55.000 i/100ms
Calculating -------------------------------------
                json    866.563 (± 0.8%) i/s    (1.15 ms/i) -      4.350k in   5.020138s
                  oj    643.567 (± 0.8%) i/s    (1.55 ms/i) -      3.264k in   5.072101s
          Oj::Parser    777.346 (± 3.5%) i/s    (1.29 ms/i) -      3.900k in   5.023933s
           rapidjson    557.158 (± 0.7%) i/s    (1.79 ms/i) -      2.805k in   5.034731s

Comparison:
                json:      866.6 i/s
          Oj::Parser:      777.3 i/s - 1.11x  slower
                  oj:      643.6 i/s - 1.35x  slower
           rapidjson:      557.2 i/s - 1.56x  slower

== Parsing citm_catalog.json (1727030 bytes)
ruby 3.4.0dev (2024-11-06T07:59:09Z precompute-hash-wh.. 7943f98a8a) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
                json    41.000 i/100ms
                  oj    35.000 i/100ms
          Oj::Parser    40.000 i/100ms
           rapidjson    39.000 i/100ms
Calculating -------------------------------------
                json    429.216 (± 1.2%) i/s    (2.33 ms/i) -      2.173k in   5.063351s
                  oj    354.755 (± 1.1%) i/s    (2.82 ms/i) -      1.785k in   5.032374s
          Oj::Parser    465.114 (± 3.7%) i/s    (2.15 ms/i) -      2.360k in   5.081634s
           rapidjson    387.135 (± 1.3%) i/s    (2.58 ms/i) -      1.950k in   5.037787s

Comparison:
                json:      429.2 i/s
          Oj::Parser:      465.1 i/s - 1.08x  faster
           rapidjson:      387.1 i/s - 1.11x  slower
                  oj:      354.8 i/s - 1.21x  slower

[casperisfine]

Not too sure why it helps quite a lot on activitypub, but less on twitter and almost not on ctim_catalog.

[casperisfine]

Not too sure why it helps quite a lot on activitypub, but less on twitter and almost not on ctim_catalog.

Alright, after instrumenting:

citm_catalog.json:

• cache_hit: 25576
• fastpath: 1027
• slowpath: 1

twitter.json:

• cache_hit: 13345
• fastpath: 4442
• slowpath: 312

activitypub.json:

• cache_hit: 878
• fastpath: 598
• slowpath: 59

So that explain why they don't all benefit the same from this.