Optimize data properties

[MattiasBuelens]

In #16, I noticed that Stardazed Streams were more than 2x faster than this polyfill. This sparked my interest, so I set out to find where this polyfill was spending the extra time.

I set up a benchmark suite using Benchmark.js to compare the performance of this polyfill and Stardazed's implementation on the code snippet from #15. Then, I used flamebearer to create the following flame graphs:

web-streams-polyfill

@stardazed/streams

I'm not an expert, but it looks like the polyfill's reader.read() spends a lot of time in some sort of built-in Node function.

I went to compare the ReadableStreamDefaultReaderRead implementation of web-streams-polyfill and @stardazed/streams, and I only found one difference inside ReadableStreamCreateReadResult. The polyfill uses Object.defineProperty to set value and done:

  Object.defineProperty(obj, 'value', { value, enumerable: true, writable: true, configurable: true });
  Object.defineProperty(obj, 'done', { value: done, enumerable: true, writable: true, configurable: true });

While Stardazed sets those with a regular property assignment:

  result.value = value;
  result.done = done;

Indeed, that fixes the performance issue! 🎉

Benchmark results before:

> node --prof index.js

web-streams-polyfill testCount(3545) x 205 ops/sec ±1.20% (82 runs sampled) (period: 4.88ms)
web-streams-polyfill testCount(7090) x 102 ops/sec ±0.73% (76 runs sampled) (period: 9.82ms)
web-streams-polyfill testCount(14180) x 48.69 ops/sec ±2.41% (74 runs sampled) (period: 20.54ms)
web-streams-polyfill testCount(28360) x 22.74 ops/sec ±1.54% (56 runs sampled) (period: 43.97ms)
web-streams-polyfill testCount(56720) x 10.68 ops/sec ±0.92% (53 runs sampled) (period: 93.60ms)
web-streams-polyfill testCount(113440) x 5.03 ops/sec ±0.77% (28 runs sampled) (period: 198.78ms)
@stardazed/streams testCount(3545) x 835 ops/sec ±1.55% (84 runs sampled) (period: 1.20ms)
@stardazed/streams testCount(7090) x 392 ops/sec ±1.89% (80 runs sampled) (period: 2.55ms)
@stardazed/streams testCount(14180) x 174 ops/sec ±2.63% (78 runs sampled) (period: 5.76ms)
@stardazed/streams testCount(28360) x 73.70 ops/sec ±2.64% (75 runs sampled) (period: 13.57ms)
@stardazed/streams testCount(56720) x 22.85 ops/sec ±5.68% (55 runs sampled) (period: 43.77ms)
@stardazed/streams testCount(113440) x 10.51 ops/sec ±0.91% (52 runs sampled) (period: 95.12ms)
Done

Process finished with exit code 0

After:

> node --prof index.js

web-streams-polyfill testCount(3545) x 742 ops/sec ±2.47% (79 runs sampled) (period: 1.35ms)
web-streams-polyfill testCount(7090) x 362 ops/sec ±1.06% (80 runs sampled) (period: 2.76ms)
web-streams-polyfill testCount(14180) x 167 ops/sec ±1.25% (75 runs sampled) (period: 6.00ms)
web-streams-polyfill testCount(28360) x 73.14 ops/sec ±0.43% (81 runs sampled) (period: 13.67ms)
web-streams-polyfill testCount(56720) x 23.82 ops/sec ±4.17% (57 runs sampled) (period: 41.97ms)
web-streams-polyfill testCount(113440) x 11.08 ops/sec ±0.95% (54 runs sampled) (period: 90.26ms)
@stardazed/streams testCount(3545) x 819 ops/sec ±1.77% (83 runs sampled) (period: 1.22ms)
@stardazed/streams testCount(7090) x 373 ops/sec ±0.51% (79 runs sampled) (period: 2.68ms)
@stardazed/streams testCount(14180) x 167 ops/sec ±1.84% (82 runs sampled) (period: 5.99ms)
@stardazed/streams testCount(28360) x 71.80 ops/sec ±2.17% (80 runs sampled) (period: 13.93ms)
@stardazed/streams testCount(56720) x 21.08 ops/sec ±5.80% (52 runs sampled) (period: 47.43ms)
@stardazed/streams testCount(113440) x 9.35 ops/sec ±0.62% (47 runs sampled) (period: 106.98ms)
Done

Process finished with exit code 0