events: avoid cloning listeners array on every emit

[gurgunday]

This PR does 2 improvements:

• Do not clone the listeners on each emit, clone when we're either adding or removing listeners
• Even when we're adding or removing listeners, if we're not currently emitting, avoid cloning again

Results:

Branch:

./node benchmark/run.js --filter ee-emit events
events/ee-emit.js
events/ee-emit.js listeners=1 argc=0 n=2000000: 91,903,668.22922815
> events/ee-emit.js listeners=5 argc=0 n=2000000: 31,178,549.48221315
> events/ee-emit.js listeners=10 argc=0 n=2000000: 18,218,586.602051415
events/ee-emit.js listeners=1 argc=2 n=2000000: 97,625,065.27455927
> events/ee-emit.js listeners=5 argc=2 n=2000000: 30,786,518.583512284
> events/ee-emit.js listeners=10 argc=2 n=2000000: 17,759,695.723843552
events/ee-emit.js listeners=1 argc=4 n=2000000: 95,971,210.17248763
> events/ee-emit.js listeners=5 argc=4 n=2000000: 30,290,753.36889973
> events/ee-emit.js listeners=10 argc=4 n=2000000: 17,108,737.480991445
events/ee-emit.js listeners=1 argc=10 n=2000000: 93,870,086.24126433
> events/ee-emit.js listeners=5 argc=10 n=2000000: 28,639,532.56158767
> events/ee-emit.js listeners=10 argc=10 n=2000000: 16,616,102.896280617

main:

./node benchmark/run.js --filter ee-emit events
events/ee-emit.js
events/ee-emit.js listeners=1 argc=0 n=2000000: 92,364,529.17596893
> events/ee-emit.js listeners=5 argc=0 n=2000000: 29,932,147.413670897
> events/ee-emit.js listeners=10 argc=0 n=2000000: 15,313,442.157135993
events/ee-emit.js listeners=1 argc=2 n=2000000: 98,371,745.94257125
> events/ee-emit.js listeners=5 argc=2 n=2000000: 29,668,674.924437966
> events/ee-emit.js listeners=10 argc=2 n=2000000: 15,159,257.397702452
events/ee-emit.js listeners=1 argc=4 n=2000000: 96,956,966.8137633
> events/ee-emit.js listeners=5 argc=4 n=2000000: 29,187,937.01091416
> events/ee-emit.js listeners=10 argc=4 n=2000000: 14,862,263.968670348
events/ee-emit.js listeners=1 argc=10 n=2000000: 94,272,546.83507264
> events/ee-emit.js listeners=5 argc=10 n=2000000: 27,359,329.00041816
> events/ee-emit.js listeners=10 argc=10 n=2000000: 11,452,222.952059666

[codecov]

Codecov Report

❌ Patch coverage is 93.33333% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.67%. Comparing base (8ccbe8e) to head (d335209).
⚠️ Report is 95 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/events.js	93.33%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62261      +/-   ##
==========================================
- Coverage   89.68%   89.67%   -0.02%     
==========================================
  Files         676      676              
  Lines      206495   206582      +87     
  Branches    39537    39559      +22     
==========================================
+ Hits       185204   185246      +42     
- Misses      13435    13459      +24     
- Partials     7856     7877      +21     

Files with missing lines	Coverage Δ
lib/events.js	99.59% <93.33%> (-0.24%)	⬇️

... and 42 files with indirect coverage changes

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[mertcanaltin]

lgtm

[atlowChemi]

@nodejs/events cc

[aduh95]

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1813/

[atlowChemi]

Benchmark CI: ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1813

                                                                 confidence improvement accuracy (*)   (**)   (***)
events/ee-add-remove.js n=1000000 removeListener=0 newListener=0                 0.27 %       ±0.83% ±1.11%  ±1.45%
events/ee-add-remove.js n=1000000 removeListener=0 newListener=1                -0.80 %       ±0.94% ±1.25%  ±1.62%
events/ee-add-remove.js n=1000000 removeListener=1 newListener=0        ***     -5.26 %       ±1.14% ±1.52%  ±1.98%
events/ee-add-remove.js n=1000000 removeListener=1 newListener=1        ***     -3.35 %       ±1.03% ±1.37%  ±1.79%
events/ee-emit.js listeners=1 argc=0 n=2000000                            *     -4.55 %       ±3.71% ±4.95%  ±6.46%
events/ee-emit.js listeners=1 argc=10 n=2000000                                  1.05 %       ±4.99% ±6.64%  ±8.65%
events/ee-emit.js listeners=1 argc=2 n=2000000                                   1.61 %       ±4.86% ±6.47%  ±8.43%
events/ee-emit.js listeners=1 argc=4 n=2000000                                  -1.33 %       ±5.98% ±7.96% ±10.36%
events/ee-emit.js listeners=10 argc=0 n=2000000                         ***     24.87 %       ±1.61% ±2.16%  ±2.82%
events/ee-emit.js listeners=10 argc=10 n=2000000                        ***     25.90 %       ±1.60% ±2.13%  ±2.80%
events/ee-emit.js listeners=10 argc=2 n=2000000                         ***     28.21 %       ±1.85% ±2.47%  ±3.22%
events/ee-emit.js listeners=10 argc=4 n=2000000                         ***     25.31 %       ±1.80% ±2.40%  ±3.16%
events/ee-emit.js listeners=5 argc=0 n=2000000                            *      3.76 %       ±3.61% ±4.81%  ±6.29%
events/ee-emit.js listeners=5 argc=10 n=2000000                         ***    -11.13 %       ±1.93% ±2.57%  ±3.35%
events/ee-emit.js listeners=5 argc=2 n=2000000                          ***      8.34 %       ±2.79% ±3.71%  ±4.83%
events/ee-emit.js listeners=5 argc=4 n=2000000                                   2.52 %       ±2.79% ±3.74%  ±4.91%
events/ee-listen-unique.js n=1000000 events=1                            **     -2.01 %       ±1.21% ±1.62%  ±2.10%
events/ee-listen-unique.js n=1000000 events=10                                  -1.15 %       ±1.63% ±2.17%  ±2.83%
events/ee-listen-unique.js n=1000000 events=2                                    0.88 %       ±1.25% ±1.66%  ±2.16%
events/ee-listen-unique.js n=1000000 events=20                                  -0.59 %       ±1.77% ±2.36%  ±3.07%
events/ee-listen-unique.js n=1000000 events=3                                   -1.12 %       ±1.38% ±1.84%  ±2.39%
events/ee-listen-unique.js n=1000000 events=5                                    0.68 %       ±1.55% ±2.07%  ±2.69%
events/ee-listener-count-on-prototype.js n=50000000                             -0.88 %       ±2.16% ±2.87%  ±3.74%
events/ee-listeners.js raw='false' listeners=5 n=5000000                         0.03 %       ±1.87% ±2.49%  ±3.24%
events/ee-listeners.js raw='false' listeners=50 n=5000000                       -0.22 %       ±0.38% ±0.51%  ±0.67%
events/ee-listeners.js raw='true' listeners=5 n=5000000                          0.55 %       ±3.20% ±4.26%  ±5.54%
events/ee-listeners.js raw='true' listeners=50 n=5000000                         0.61 %       ±0.88% ±1.17%  ±1.53%
events/ee-once.js argc=0 n=20000000                                              0.06 %       ±0.93% ±1.24%  ±1.61%
events/ee-once.js argc=1 n=20000000                                             -1.06 %       ±1.21% ±1.62%  ±2.11%
events/ee-once.js argc=4 n=20000000                                             -0.24 %       ±0.91% ±1.21%  ±1.58%
events/ee-once.js argc=5 n=20000000                                             -0.17 %       ±1.15% ±1.53%  ±2.00%
events/eventtarget-add-remove-abort.js nListener=1 n=100000                     -0.80 %       ±6.22% ±8.28% ±10.77%
events/eventtarget-add-remove-abort.js nListener=10 n=100000                     0.16 %       ±1.59% ±2.11%  ±2.75%
events/eventtarget-add-remove-abort.js nListener=5 n=100000                      0.47 %       ±2.42% ±3.21%  ±4.19%
events/eventtarget-add-remove.js nListener=1 n=100000                     *     -5.65 %       ±5.52% ±7.34%  ±9.56%
events/eventtarget-add-remove.js nListener=10 n=100000                          -1.06 %       ±1.71% ±2.28%  ±2.97%
events/eventtarget-add-remove.js nListener=5 n=100000                           -0.19 %       ±2.61% ±3.47%  ±4.52%
events/eventtarget-creation.js n=1000000                                         0.37 %       ±1.85% ±2.47%  ±3.21%
events/eventtarget.js listeners=1 n=1000000                                     -0.24 %       ±1.75% ±2.33%  ±3.04%
events/eventtarget.js listeners=10 n=1000000                                     0.20 %       ±0.95% ±1.26%  ±1.65%
events/eventtarget.js listeners=5 n=1000000                                      0.15 %       ±1.17% ±1.56%  ±2.03%

Be aware that when doing many comparisons the risk of a false-positive
result increases. In this case, there are 41 comparisons, you can thus
expect the following amount of false-positive results:
  2.05 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.41 false positives, when considering a   1% risk acceptance (**, ***),
  0.04 false positives, when considering a 0.1% risk acceptance (***)

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/71889/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/72099/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/72105/

[nodejs-github-bot]

Landed in 7ffbb76