json-escape-simd

Optimized SIMD routines for escaping JSON strings. This repository contains the json-escape-simd crate, comparison fixtures, and Criterion benches against commonly used alternatives.

Important

On aarch64 NEON hosts the available register width is 128 bits, which is narrower than the lookup table this implementation prefers. As a result the SIMD path may not outperform the generic fallback, which is reflected in the benchmark numbers below.

On some modern macOS devices with larger register numbers, the SIMD path may outperform the generic fallback, see the M3 max benchmark below.

Note

The force_aarch64_neon feature flag can be used to force use of the neon implementation on aarch64. This is useful for the benchmark.

Benchmarks

Numbers below come from cargo bench runs on GitHub Actions hardware. Criterion reports are summarized to make it easier to spot relative performance. "vs fastest" shows how much slower each implementation is compared to the fastest entry in the table (1.00× means fastest).

GitHub Actions x86_64 (ubuntu-latest)

AVX2 enabled.

RxJS payload (~10k iterations)

Implementation	Median time	vs fastest
escape simd	341.18 µs	1.00×
escape v_jsonescape	555.47 µs	1.63×
escape generic	656.85 µs	1.93×
serde_json	744.75 µs	2.18×
json-escape	777.15 µs	2.28×

Fixtures payload (~300 iterations)

Implementation	Median time	vs fastest
escape simd	12.67 ms	1.00×
escape v_jsonescape	20.58 ms	1.62×
escape generic	22.57 ms	1.78×
serde_json	24.52 ms	1.94×
json-escape	26.97 ms	2.13×

GitHub Actions aarch64 (ubuntu-24.04-arm)

Neon enabled.

RxJS payload (~10k iterations)

Implementation	Median time	vs fastest
escape generic	546.89 µs	1.00×
escape simd	589.29 µs	1.08×
serde_json	612.33 µs	1.12×
json-escape	624.66 µs	1.14×
escape v_jsonescape	789.14 µs	1.44×

Fixtures payload (~300 iterations)

Implementation	Median time	vs fastest
escape generic	17.81 ms	1.00×
serde_json	19.77 ms	1.11×
json-escape	20.84 ms	1.17×
escape simd	21.04 ms	1.18×
escape v_jsonescape	25.57 ms	1.44×

GitHub Actions macOS (macos-latest)

Apple M1 chip

RxJS payload (~10k iterations)

Implementation	Median time	vs fastest
escape generic	759.07 µs	1.00×
escape simd	764.98 µs	1.01×
serde_json	793.91 µs	1.05×
json-escape	868.21 µs	1.14×
escape v_jsonescape	926.00 µs	1.22×

Fixtures payload (~300 iterations)

Implementation	Median time	vs fastest
serde_json	26.41 ms	1.00×
escape generic	26.43 ms	1.00×
escape simd	26.42 ms	1.00×
json-escape	28.94 ms	1.10×
escape v_jsonescape	29.22 ms	1.11×

Apple M3 Max

RxJS payload (~10k iterations)

Implementation	Median time	vs fastest
escape simd	307.20 µs	1.00×
escape generic	490.00 µs	1.60×
serde_json	570.35 µs	1.86×
escape v_jsonescape	599.72 µs	1.95×
json-escape	644.73 µs	2.10×

Fixtures payload (~300 iterations)

Implementation	Median time	vs fastest
escape generic	17.89 ms	1.00×
escape simd	17.92 ms	1.00×
serde_json	19.78 ms	1.11×
escape v_jsonescape	21.09 ms	1.18×
json-escape	22.43 ms	1.25×