util: improve inspect performance

[BridgeAR]

This improves a slow code part in util.inspect by directly
retrieving the Symbol.toStringTag and by optimizing some code
paths.

I benchmarked this with #20007 applied.

'use strict';

const util = require('util');

let i = 0;
const obj = {};

while (i++ < 100000) {
  obj[i] = {
    a: new Set([1, {}]),
    b: [],
    c: [1, 2],
    d: true
  };
}

for (const k of Object.keys(obj)) {
  obj[k].obj = obj;
}

console.time('run');
util.inspect(obj);
console.timeEnd('run');

// node$ ./slow t.js
// run: 692.284ms
// run: 681.384ms
// run: 685.455ms

// node$ ./fast t.js
// run: 645.635ms
// run: 640.754ms
// run: 648.319ms

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[BridgeAR]

CI https://ci.nodejs.org/job/node-test-pull-request/14258/

[jasnell]

Can you post the benchmark results?

[BridgeAR]

@jasnell I posted them in the description below the code?

[BridgeAR]

CI https://ci.nodejs.org/job/node-test-pull-request/14261/

[jasnell]

oh, missed that. Is there not an existing benchmark script that works with compare.js? Seeing those results would be more reliable I think.

[BridgeAR]

Just a few runs:

                                                                        confidence improvement accuracy (*)    (**)   (***)
 util/inspect.js option='colors' method='Array' n=100000                         *      2.44 %       ±2.11%  ±3.10%  ±4.73%
 util/inspect.js option='colors' method='Date' n=100000                        ***     12.46 %       ±3.01%  ±4.22%  ±5.95%
 util/inspect.js option='colors' method='Error' n=100000                       ***     19.52 %       ±2.76%  ±3.86%  ±5.44%
 util/inspect.js option='colors' method='Object_deep_ln' n=100000               **      3.17 %       ±1.81%  ±2.58%  ±3.74%
 util/inspect.js option='colors' method='Object_empty' n=100000                 **     22.80 %      ±11.70% ±17.12% ±25.93%
 util/inspect.js option='colors' method='Object' n=100000                        *      6.63 %       ±6.01%  ±8.62% ±12.65%
 util/inspect.js option='colors' method='Set' n=100000                                  2.63 %       ±2.85%  ±3.98%  ±5.59%
 util/inspect.js option='colors' method='String_boxed' n=100000                ***     12.94 %       ±3.28%  ±4.67%  ±6.74%
 util/inspect.js option='colors' method='String_complex' n=100000                       3.83 %       ±4.73%  ±6.66%  ±9.49%
 util/inspect.js option='colors' method='TypedArray_extra' n=100000                     0.73 %       ±2.67%  ±3.72%  ±5.23%
 util/inspect.js option='colors' method='TypedArray' n=100000                    *      4.21 %       ±3.80%  ±5.57%  ±8.49%
 util/inspect.js option='none' method='Array' n=100000                         ***      4.72 %       ±2.03%  ±2.90%  ±4.22%
 util/inspect.js option='none' method='Date' n=100000                          ***     15.46 %       ±2.86%  ±4.25%  ±6.59%
 util/inspect.js option='none' method='Error' n=100000                         ***     23.22 %       ±2.73%  ±3.82%  ±5.38%
 util/inspect.js option='none' method='Object_deep_ln' n=100000                ***      7.70 %       ±2.91%  ±4.19%  ±6.21%
 util/inspect.js option='none' method='Object_empty' n=100000                   **     16.26 %       ±9.35% ±13.45% ±19.83%
 util/inspect.js option='none' method='Object' n=100000                          *     14.39 %      ±11.48% ±16.93% ±26.01%
 util/inspect.js option='none' method='Set' n=100000                           ***      7.50 %       ±2.50%  ±3.50%  ±4.95%
 util/inspect.js option='none' method='String_boxed' n=100000                  ***     11.00 %       ±3.54%  ±5.04%  ±7.33%
 util/inspect.js option='none' method='String_complex' n=100000                         0.61 %       ±1.59%  ±2.23%  ±3.15%
 util/inspect.js option='none' method='TypedArray_extra' n=100000                       1.87 %       ±2.54%  ±3.55%  ±5.00%
 util/inspect.js option='none' method='TypedArray' n=100000                     **      7.09 %       ±4.82%  ±7.01% ±10.52%
 util/inspect.js option='showHidden' method='Array' n=100000                   ***      3.04 %       ±1.23%  ±1.74%  ±2.50%
 util/inspect.js option='showHidden' method='Date' n=100000                    ***     15.47 %       ±2.79%  ±3.90%  ±5.48%
 util/inspect.js option='showHidden' method='Error' n=100000                     *      2.97 %       ±2.51%  ±3.54%  ±5.05%
 util/inspect.js option='showHidden' method='Object_deep_ln' n=100000            *     11.97 %       ±8.53% ±12.58% ±19.30%
 util/inspect.js option='showHidden' method='Object_empty' n=100000            ***     18.51 %       ±4.08%  ±5.92%  ±8.86%
 util/inspect.js option='showHidden' method='Object' n=100000                  ***      6.28 %       ±2.20%  ±3.05%  ±4.25%
 util/inspect.js option='showHidden' method='Set' n=100000                     ***      9.35 %       ±4.42%  ±6.19%  ±8.73%
 util/inspect.js option='showHidden' method='String_boxed' n=100000            ***      9.79 %       ±2.57%  ±3.64%  ±5.25%
 util/inspect.js option='showHidden' method='String_complex' n=100000                   0.32 %       ±3.38%  ±4.81%  ±6.95%
 util/inspect.js option='showHidden' method='TypedArray_extra' n=100000                 1.49 %       ±1.69%  ±2.36%  ±3.31%
 util/inspect.js option='showHidden' method='TypedArray' n=100000              ***      4.54 %       ±1.78%  ±2.49%  ±3.48%

[BridgeAR]

Rebased

New CI https://ci.nodejs.org/job/node-test-pull-request/14332/

[jasnell]

CI failed. PTAL

[BridgeAR]

CI https://ci.nodejs.org/job/node-test-pull-request/14356/

[BridgeAR]

Landed in ad1d105