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fix(subject): Faster subscriptions management in Subject#7240

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benlesh merged 2 commits intoReactiveX:masterfrom
dubzzz:faster-subjects-unsub-2
Apr 4, 2023
Merged

fix(subject): Faster subscriptions management in Subject#7240
benlesh merged 2 commits intoReactiveX:masterfrom
dubzzz:faster-subjects-unsub-2

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@dubzzz
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@dubzzz dubzzz commented Mar 30, 2023

Description:

The current implementation of the Subject was backing itself on an array of observers. When one observer unsubscribed itself, it was performing a linear scan on the array of observers and dropping the item from the array of observers. The algorithm complexity of this operation was O(n) with n being the number of observers connected to the Subject.

It caused code like:

const allSubscriptions = [];
const source = new Subject();
for (let index = 0 ; index !== 1_000_000 ; ++index) {
  allSubscriptions.push(source.subscribe()); // rather quick
}
for (const subscription of allSubscriptions) {
  subscription.unsubscribe(); // taking very long
}

The proposed approach consists into changing our backing collection (an array) into a Map. But we lose somehow the set capability on subject.observers (might possibly be patched in some way).

The command cross-env TS_NODE_PROJECT=tsconfig.mocha.json mocha --config spec/support/.mocharc.js "spec/**/Subje*-spec.ts" with the new test added:

  • Now: 497ms
  • Before: 10s

BREAKING CHANGE:

Subject.observers has been impacted. If needed we can probably make it backward compatible in some ways. Here is what changed:

  • Now a getter property, was previously a basic property
  • The value change from one call to another -we recompute it anytime we access it)
  • There is no setter anymore
  • The value is never null

Related issue (if exists):

@dubzzz
fix(subject): Faster subscriptions management in Subject
8614537 
The current implementation of the Subject was backing itself on an array of observers. When one observer unsubscribed itself, it was performing a linear scan on the array of observers and dropping the item from the array of observers. The algorithm complexity of this operation was O(n) with n being the number of observers connected to the Subject.

It caused code like:

```js
const allSubscriptions = [];
const source = new Subject();
for (let index = 0 ; index !== 1_000_000 ; ++index) {
  allSubscriptions.push(source.subscribe()); // rather quick
}
for (const subscription of allSubscriptions) {
  subscription.unsubscribe(); // taking very long
}
```

The proposed approach consists into changing our backing collection (an array) into a Map. But we lose somehow the set capability on subject.observers (might possibly be patched in some way).

Following that change the command `cross-env TS_NODE_PROJECT=tsconfig.mocha.json mocha --config spec/support/.mocharc.js "spec/**/Subje*-spec.ts"` passed to 452ms from 10s.
@dubzzz
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dubzzz commented Mar 30, 2023 •
edited
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By the way I started to run some benchmarks against the new code and the master I took my branch from.

Here is the code I used 
// @ts-check
const { Bench } = require('tinybench');
const { Subject: SubjectMaster } = require('./dist-master/cjs');
const { Subject: SubjectPr } = require('./dist/cjs');

async function run() {
  const numIterations = 10_000;
  const bench = new Bench({ warmupIterations: Math.ceil(numIterations / 20), iterations: numIterations });

  bench.add('[master] Creating Subject', () => {
    new SubjectMaster();
  });
  bench.add('[pr] Creating Subject', () => {
    new SubjectPr();
  });

  bench.add('[master] 0 subscribed, 1 next', () => {
    const source = new SubjectMaster();
    source.next(1);
  });
  bench.add('[pr] 0 subscribed, 1 next', () => {
    const source = new SubjectPr();
    source.next(1);
  });

  bench.add('[master] 0 subscribed, 100 next', () => {
    const source = new SubjectMaster();
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
  });
  bench.add('[pr] 0 subscribed, 100 next', () => {
    const source = new SubjectPr();
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
  });

  bench.add('[master] 1 subscribed, 1 next', () => {
    const source = new SubjectMaster();
    const subscription = source.asObservable().subscribe();
    source.next(1);
    subscription.unsubscribe();
  });
  bench.add('[pr] 1 subscribed, 1 next', () => {
    const source = new SubjectPr();
    const subscription = source.asObservable().subscribe();
    source.next(1);
    subscription.unsubscribe();
  });

  bench.add('[master] 1 subscribed, 100 next', () => {
    const source = new SubjectMaster();
    const subscription = source.asObservable().subscribe();
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
    subscription.unsubscribe();
  });
  bench.add('[pr] 1 subscribed, 100 next', () => {
    const source = new SubjectPr();
    const subscription = source.asObservable().subscribe();
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
    subscription.unsubscribe();
  });

  bench.add('[master] 3 subscribed, 1 next', () => {
    const source = new SubjectMaster();
    const s1 = source.asObservable().subscribe();
    const s2 = source.asObservable().subscribe();
    const s3 = source.asObservable().subscribe();
    source.next(1);
    s1.unsubscribe();
    s2.unsubscribe();
    s3.unsubscribe();
  });
  bench.add('[pr] 3 subscribed, 1 next', () => {
    const source = new SubjectPr();
    const s1 = source.asObservable().subscribe();
    const s2 = source.asObservable().subscribe();
    const s3 = source.asObservable().subscribe();
    source.next(1);
    s1.unsubscribe();
    s2.unsubscribe();
    s3.unsubscribe();
  });

  bench.add('[master] 3 subscribed, 100 next', () => {
    const source = new SubjectMaster();
    const s1 = source.asObservable().subscribe();
    const s2 = source.asObservable().subscribe();
    const s3 = source.asObservable().subscribe();
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
    s1.unsubscribe();
    s2.unsubscribe();
    s3.unsubscribe();
  });
  bench.add('[pr] 3 subscribed, 100 next', () => {
    const source = new SubjectPr();
    const s1 = source.asObservable().subscribe();
    const s2 = source.asObservable().subscribe();
    const s3 = source.asObservable().subscribe();
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
    s1.unsubscribe();
    s2.unsubscribe();
    s3.unsubscribe();
  });

  bench.add('[master] 10 subscribed, 1 next', () => {
    const source = new SubjectMaster();
    const s = [];
    for (let i = 0; i !== 10; ++i) {
      s.push(source.asObservable().subscribe());
    }
    source.next(1);
    for (const e of s) {
      e.unsubscribe();
    }
  });
  bench.add('[pr] 10 subscribed, 1 next', () => {
    const source = new SubjectPr();
    const s = [];
    for (let i = 0; i !== 10; ++i) {
      s.push(source.asObservable().subscribe());
    }
    source.next(1);
    for (const e of s) {
      e.unsubscribe();
    }
  });

  bench.add('[master] 10 subscribed, 100 next', () => {
    const source = new SubjectMaster();
    const s = [];
    for (let i = 0; i !== 10; ++i) {
      s.push(source.asObservable().subscribe());
    }
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
    for (const e of s) {
      e.unsubscribe();
    }
  });
  bench.add('[pr] 10 subscribed, 100 next', () => {
    const source = new SubjectPr();
    const s = [];
    for (let i = 0; i !== 10; ++i) {
      s.push(source.asObservable().subscribe());
    }
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
    for (const e of s) {
      e.unsubscribe();
    }
  });

  bench.add('[master] 100 subscribed, 1 next', () => {
    const source = new SubjectMaster();
    const s = [];
    for (let i = 0; i !== 100; ++i) {
      s.push(source.asObservable().subscribe());
    }
    source.next(1);
    for (const e of s) {
      e.unsubscribe();
    }
  });
  bench.add('[pr] 100 subscribed, 1 next', () => {
    const source = new SubjectPr();
    const s = [];
    for (let i = 0; i !== 100; ++i) {
      s.push(source.asObservable().subscribe());
    }
    source.next(1);
    for (const e of s) {
      e.unsubscribe();
    }
  });

  bench.add('[master] 100 subscribed, 100 next', () => {
    const source = new SubjectMaster();
    const s = [];
    for (let i = 0; i !== 100; ++i) {
      s.push(source.asObservable().subscribe());
    }
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
    for (const e of s) {
      e.unsubscribe();
    }
  });
  bench.add('[pr] 100 subscribed, 100 next', () => {
    const source = new SubjectPr();
    const s = [];
    for (let i = 0; i !== 100; ++i) {
      s.push(source.asObservable().subscribe());
    }
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
    for (const e of s) {
      e.unsubscribe();
    }
  });

  bench.add('[master] 1000 subscribed, 1 next', () => {
    const source = new SubjectMaster();
    const s = [];
    for (let i = 0; i !== 1000; ++i) {
      s.push(source.asObservable().subscribe());
    }
    source.next(1);
    for (const e of s) {
      e.unsubscribe();
    }
  });
  bench.add('[pr] 1000 subscribed, 1 next', () => {
    const source = new SubjectPr();
    const s = [];
    for (let i = 0; i !== 1000; ++i) {
      s.push(source.asObservable().subscribe());
    }
    source.next(1);
    for (const e of s) {
      e.unsubscribe();
    }
  });

  bench.add('[master] 1000 subscribed, 100 next', () => {
    const source = new SubjectMaster();
    const s = [];
    for (let i = 0; i !== 1000; ++i) {
      s.push(source.asObservable().subscribe());
    }
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
    for (const e of s) {
      e.unsubscribe();
    }
  });
  bench.add('[pr] 1000 subscribed, 100 next', () => {
    const source = new SubjectPr();
    const s = [];
    for (let i = 0; i !== 1000; ++i) {
      s.push(source.asObservable().subscribe());
    }
    for (let i = 0; i !== 100; ++i) {
      source.next(i);
    }
    for (const e of s) {
      e.unsubscribe();
    }
  });

  await bench.warmup();
  await bench.run();

  console.table(
    bench.tasks.map(({ name, result }) => {
      return {
        Name: name,
        Mean: result?.mean,
        P75: result?.p75,
        P99: result?.p99,
        RME: result?.rme,
      };
    })
  );
}
run();

Here are the results for the current version of the code:

┌─────────┬──────────────────────────────────────┬────────────────────────┬────────────────────────┬───────────────────────┬────────────────────┐
│ (index) │                 Name                 │          Mean          │          P75           │          P99          │        RME         │
├─────────┼──────────────────────────────────────┼────────────────────────┼────────────────────────┼───────────────────────┼────────────────────┤
│    0    │     '[master] Creating Subject'      │ 0.00015643814199720028 │ 0.00019999966025352478 │ 0.0003000004217028618 │ 11.589776920801196 │
│    1    │       '[pr] Creating Subject'        │ 0.00017207796397903874 │ 0.00019999966025352478 │ 0.0005000000819563866 │ 0.8590171745396832 │
│    2    │   '[master] 0 subscribed, 1 next'    │ 0.00020557814425434853 │ 0.0002000005915760994  │ 0.0005000000819563866 │ 1.3377641081389615 │
│    3    │     '[pr] 0 subscribed, 1 next'      │ 0.00018017834274192457 │ 0.0002000005915760994  │ 0.0005000000819563866 │ 0.7602265034322395 │
│    4    │  '[master] 0 subscribed, 100 next'   │ 0.0030202487889903437  │ 0.0029999995604157448  │ 0.005300000309944153  │ 0.590282723735076  │
│    5    │    '[pr] 0 subscribed, 100 next'     │ 0.0004527702810480123  │ 0.0005000000819563866  │ 0.0008999994024634361 │ 0.5861990278579561 │
│    6    │   '[master] 1 subscribed, 1 next'    │ 0.0008216253886610409  │ 0.0007999995723366737  │ 0.001600000075995922  │ 0.6719833246454169 │
│    7    │     '[pr] 1 subscribed, 1 next'      │  0.000856679151685021  │ 0.0008000005036592484  │ 0.0015000002458691597 │ 0.7766441850042467 │
│    8    │  '[master] 1 subscribed, 100 next'   │  0.004788513404096101  │  0.004699999466538429  │ 0.008899999782443047  │ 0.7056875628905762 │
│    9    │    '[pr] 1 subscribed, 100 next'     │ 0.0014018038008829956  │ 0.0013999994844198227  │ 0.0022999998182058334 │ 0.8684742543095227 │
│   10    │   '[master] 3 subscribed, 1 next'    │ 0.0018978834599352103  │ 0.0017999997362494469  │ 0.0034000007435679436 │ 3.032935309575753  │
│   11    │     '[pr] 3 subscribed, 1 next'      │ 0.0017642026010910529  │ 0.0016999999061226845  │ 0.003200000151991844  │ 0.5353075708343223 │
│   12    │  '[master] 3 subscribed, 100 next'   │  0.00802172429488669   │  0.007799999788403511  │  0.01489999983459711  │ 0.5660223830939138 │
│   13    │    '[pr] 3 subscribed, 100 next'     │  0.003131604704897833  │ 0.0030000004917383194  │ 0.005499999970197678  │ 1.134493567559593  │
│   14    │   '[master] 10 subscribed, 1 next'   │  0.004826806852278755  │  0.004499000497162342  │ 0.008899999782443047  │ 0.6422339682792549 │
│   15    │     '[pr] 10 subscribed, 1 next'     │  0.004576598058776545  │ 0.0044999998062849045  │ 0.0074000004678964615 │ 1.3101714281276127 │
│   16    │  '[master] 10 subscribed, 100 next'  │  0.020022055576250558  │  0.01850000023841858   │  0.03910000063478947  │ 0.6652153397296293 │
│   17    │    '[pr] 10 subscribed, 100 next'    │  0.009184353557200084  │  0.008299999870359898  │ 0.015599999576807022  │ 2.183817921324249  │
│   18    │  '[master] 100 subscribed, 1 next'   │  0.04320903015868642   │  0.038200000301003456  │  0.10059900023043156  │ 1.2233526482136148 │
│   19    │    '[pr] 100 subscribed, 1 next'     │  0.03559318009971064   │  0.03399999998509884   │  0.07059899996966124  │ 0.7623208783019286 │
│   20    │ '[master] 100 subscribed, 100 next'  │  0.17524525809325278   │   0.1589989997446537   │  0.36219900008291006  │ 0.6542612434974838 │
│   21    │   '[pr] 100 subscribed, 100 next'    │  0.07490052990522236   │  0.06799900066107512   │  0.15750000067055225  │ 0.8771896860089285 │
│   22    │  '[master] 1000 subscribed, 1 next'  │   1.5466663203015925   │   1.3917950000613928   │  3.0632890006527305   │ 1.1953427047583378 │
│   23    │    '[pr] 1000 subscribed, 1 next'    │   0.4354844354032539   │   0.3509990004822612   │  1.4115949999541044   │ 1.3006120132927175 │
│   24    │ '[master] 1000 subscribed, 100 next' │   2.8816406472022646   │   3.048589000478387    │   5.759379000402987   │  0.58972696843935  │
│   25    │   '[pr] 1000 subscribed, 100 next'   │   1.3074916874016635   │   1.176095999777317    │  2.6631909999996424   │ 0.7865946049284476 │
└─────────┴──────────────────────────────────────┴────────────────────────┴────────────────────────┴───────────────────────┴────────────────────┘
For previous version

It used for (const observer of this.snapshotedObservers) in next/error/complete.
Instead of for (let i = 0; i !== snapshotedObservers.length; ++i).

┌─────────┬──────────────────────────────────────┬────────────────────────┬───────────────────────┬───────────────────────┬────────────────────┐
│ (index) │                 Name                 │          Mean          │          P75          │          P99          │        RME         │
├─────────┼──────────────────────────────────────┼────────────────────────┼───────────────────────┼───────────────────────┼────────────────────┤
│    0    │     '[master] Creating Subject'      │ 0.00012953836437439974 │ 0.000100000761449337  │ 0.0003000004217028618 │ 0.8079907019422605 │
│    1    │       '[pr] Creating Subject'        │ 0.00017635711767006987 │ 0.0002000005915760994 │ 0.0004000002518296242 │ 0.8289423819308911 │
│    2    │   '[master] 0 subscribed, 1 next'    │ 0.00020459377653131344 │ 0.0002000005915760994 │ 0.0005000000819563866 │ 1.1378771813981523 │
│    3    │     '[pr] 0 subscribed, 1 next'      │ 0.00020221618217370962 │ 0.0002000005915760994 │ 0.0005000000819563866 │ 0.6810397390682086 │
│    4    │  '[master] 0 subscribed, 100 next'   │ 0.0029463214406694736  │ 0.0028999997302889824 │ 0.005300000309944153  │ 0.5257643196869795 │
│    5    │    '[pr] 0 subscribed, 100 next'     │  0.002991678455293176  │ 0.0028999997302889824 │ 0.006000000052154064  │ 0.5867012451076267 │
│    6    │   '[master] 1 subscribed, 1 next'    │ 0.0007954250431398286  │ 0.000700000673532486  │ 0.001600000075995922  │ 0.8766148496955309 │
│    7    │     '[pr] 1 subscribed, 1 next'      │ 0.0008213868146737953  │ 0.000700000673532486  │ 0.0016999999061226845 │ 1.1956179944223218 │
│    8    │  '[master] 1 subscribed, 100 next'   │  0.004908873666542814  │ 0.004700000397861004  │ 0.009000000543892384  │ 0.590427156123814  │
│    9    │    '[pr] 1 subscribed, 100 next'     │  0.004821027538623853  │ 0.004699999466538429  │ 0.008899999782443047  │ 1.346060178011175  │
│   10    │   '[master] 3 subscribed, 1 next'    │ 0.0017776441528556996  │ 0.001700000837445259  │ 0.0032999999821186066 │ 0.5591522908763634 │
│   11    │     '[pr] 3 subscribed, 1 next'      │  0.002093957002878406  │ 0.002199999988079071  │ 0.0035999994724988937 │  3.92953070123866  │
│   12    │  '[master] 3 subscribed, 100 next'   │  0.008743048678321383  │ 0.008100000210106373  │ 0.015899999998509884  │ 0.6343904943811376 │
│   13    │    '[pr] 3 subscribed, 100 next'     │  0.008495988327560293  │ 0.007900000549852848  │ 0.015999999828636646  │ 0.8790439256253967 │
│   14    │   '[master] 10 subscribed, 1 next'   │ 0.0043729048539165325  │  0.00430000014603138  │ 0.008100000210106373  │ 0.9333949527437183 │
│   15    │     '[pr] 10 subscribed, 1 next'     │ 0.0045709372217430525  │ 0.0044999998062849045 │ 0.008200000040233135  │ 0.5809235637555371 │
│   16    │  '[master] 10 subscribed, 100 next'  │  0.021834660001977563  │  0.01919999998062849  │ 0.042500000447034836  │ 0.7986149010500317 │
│   17    │    '[pr] 10 subscribed, 100 next'    │  0.019986633528925612  │ 0.019100000150501728  │  0.03870000038295984  │ 0.609131840525482  │
│   18    │  '[master] 100 subscribed, 1 next'   │  0.03534182979824568   │  0.03379999939352274  │  0.07440000027418137  │ 0.7415500120208155 │
│   19    │    '[pr] 100 subscribed, 1 next'     │   0.0387508219938843   │  0.0353990001603961   │   0.075399000197649   │ 0.8391257949669215 │
│   20    │ '[master] 100 subscribed, 100 next'  │   0.201847207995411    │  0.19289899989962578  │  0.4039989998564124   │ 0.5170851608490207 │
│   21    │   '[pr] 100 subscribed, 100 next'    │  0.16869005630528555   │  0.1540999999269843   │  0.41039799991995096  │ 0.6719182298208819 │
│   22    │  '[master] 1000 subscribed, 1 next'  │   1.5724196430016308   │   1.404395000077784   │   2.982989000156522   │ 1.3230435037243793 │
│   23    │    '[pr] 1000 subscribed, 1 next'    │  0.38491055010296404   │  0.34489900059998035  │  0.7981970002874732   │ 0.7066891146691681 │
│   24    │ '[master] 1000 subscribed, 100 next' │   3.4955092910996637   │   3.423287999816239   │  12.234055999666452   │ 1.1369695485258002 │
│   25    │   '[pr] 1000 subscribed, 100 next'   │   1.7436433385007084   │  1.9780930001288652   │   3.649686999619007   │ 0.534574044984933  │
└─────────┴──────────────────────────────────────┴────────────────────────┴───────────────────────┴───────────────────────┴────────────────────┘
For previous previous version

It used snapshotedObservers = undefined for dirty instead of relying on a separate flag.

┌─────────┬──────────────────────────────────────┬────────────────────────┬────────────────────────┬───────────────────────┬────────────────────┐
│ (index) │                 Name                 │          Mean          │          P75           │          P99          │        RME         │
├─────────┼──────────────────────────────────────┼────────────────────────┼────────────────────────┼───────────────────────┼────────────────────┤
│    0    │     '[master] Creating Subject'      │ 0.00013438917905651826 │  0.000100000761449337  │ 0.0003000004217028618 │ 1.3808905613853422 │
│    1    │       '[pr] Creating Subject'        │ 0.0001629036470950004  │ 0.00019999966025352478 │ 0.0004000002518296242 │ 1.0150111866666365 │
│    2    │   '[master] 0 subscribed, 1 next'    │ 0.00020070787559535244 │ 0.0002000005915760994  │ 0.0004000002518296242 │ 1.1623744271141512 │
│    3    │     '[pr] 0 subscribed, 1 next'      │ 0.00022203701635951922 │ 0.0002000005915760994  │ 0.0005000000819563866 │ 0.6444068421817747 │
│    4    │  '[master] 0 subscribed, 100 next'   │  0.002925753821364004  │ 0.0028999997302889824  │ 0.004700000397861004  │ 0.6675482695040803 │
│    5    │    '[pr] 0 subscribed, 100 next'     │ 0.0029455148154576153  │  0.00279999990016222   │ 0.005699999630451202  │ 0.7283875789421631 │
│    6    │   '[master] 1 subscribed, 1 next'    │ 0.0008836313455785351  │ 0.0008999994024634361  │ 0.0016999999061226845 │ 2.307640350615159  │
│    7    │     '[pr] 1 subscribed, 1 next'      │ 0.0007251301898595778  │  0.000700000673532486  │ 0.0014000004157423973 │ 0.5369440230363686 │
│    8    │  '[master] 1 subscribed, 100 next'   │  0.004941166842718795  │ 0.0046000005677342415  │ 0.009399999864399433  │ 0.6682103605826338 │
│    9    │    '[pr] 1 subscribed, 100 next'     │  0.005783039856998958  │  0.006799999624490738  │ 0.010099999606609344  │ 2.760054332032325  │
│   10    │   '[master] 3 subscribed, 1 next'    │ 0.0016769644515204616  │  0.001600000075995922  │ 0.0027000000700354576 │ 1.227012134545868  │
│   11    │     '[pr] 3 subscribed, 1 next'      │ 0.0016556261053327526  │  0.001600000075995922  │ 0.0029999995604157448 │ 0.5915214577550268 │
│   12    │  '[master] 3 subscribed, 100 next'   │  0.008435009342731267  │  0.007799999788403511  │ 0.015899999998509884  │ 0.7330348607559893 │
│   13    │    '[pr] 3 subscribed, 100 next'     │  0.008118471813221768  │  0.007699999958276749  │ 0.015999999828636646  │ 0.6762544367799905 │
│   14    │   '[master] 10 subscribed, 1 next'   │  0.004619361542797714  │  0.00430000014603138   │ 0.008700000122189522  │ 0.6865332120986498 │
│   15    │     '[pr] 10 subscribed, 1 next'     │  0.004598094030228484  │  0.004500000737607479  │ 0.007698999717831612  │ 0.6325973043805078 │
│   16    │  '[master] 10 subscribed, 100 next'  │  0.022130750062305478  │  0.018799999728798866  │  0.04339999984949827  │ 2.150985307759586  │
│   17    │    '[pr] 10 subscribed, 100 next'    │  0.019448945272817215  │  0.018399999476969242  │  0.03890000004321337  │ 0.7046440921562903 │
│   18    │  '[master] 100 subscribed, 1 next'   │  0.03653645173544088   │  0.034199999645352364  │  0.07739999983459711  │ 0.8187488838632786 │
│   19    │    '[pr] 100 subscribed, 1 next'     │  0.036315523351770795  │  0.034500000067055225  │  0.07210000045597553  │ 0.7989402616875521 │
│   20    │ '[master] 100 subscribed, 100 next'  │   0.2089092620057985   │  0.19649900030344725   │  0.4164990000426769   │ 0.5958587469091308 │
│   21    │   '[pr] 100 subscribed, 100 next'    │   0.1770285663041286   │  0.15689999982714653   │  0.43609900027513504  │ 0.9649566330973336 │
│   22    │  '[master] 1000 subscribed, 1 next'  │   1.5781902391046285   │   1.4167949995025992   │  3.3108860002830625   │ 0.9724061547552825 │
│   23    │    '[pr] 1000 subscribed, 1 next'    │  0.39690413890369236   │  0.35139899980276823   │  0.8345969999209046   │ 0.7682173831587366 │
│   24    │ '[master] 1000 subscribed, 100 next' │   3.2799664519059473   │   3.4474869994446635   │   6.460476000793278   │ 0.4891545002124059 │
│   25    │   '[pr] 1000 subscribed, 100 next'   │   1.9804286305020564   │   2.026992999948561    │   6.734376000240445   │ 1.2118338955923968 │
└─────────┴──────────────────────────────────────┴────────────────────────┴────────────────────────┴───────────────────────┴────────────────────┘

All these measurements have been done on a codespace of GitHub against 10k runs. I'll try to issue one against even more runs.

@dubzzz dubzzz mentioned this pull request Mar 30, 2023
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dubzzz commented Mar 30, 2023 •
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Same benchmark but with 1,000,000 iterations:

┌─────────┬─────────────────────────────────────┬────────────────────────┬────────────────────────┬────────────────────────┬─────────────────────┐
│ (index) │                Name                 │          Mean          │          P75           │          P99           │         RME         │
├─────────┼─────────────────────────────────────┼────────────────────────┼────────────────────────┼────────────────────────┼─────────────────────┤
│    0    │     '[master] Creating Subject'     │ 0.00013759328511377957 │ 0.00019999966025352478 │ 0.00039999932050704956 │ 0.33501543849907456 │
│    1    │       '[pr] Creating Subject'       │ 0.00022728897428750432 │ 0.00029999949038028717 │ 0.0005000000819563866  │  4.775231779343227  │
│    2    │   '[master] 0 subscribed, 1 next'   │  0.000341275965122363  │ 0.0004000002518296242  │  0.000599999912083149  │  1.114983178579931  │
│    3    │     '[pr] 0 subscribed, 1 next'     │ 0.00019064141631205663 │ 0.0002000005915760994  │ 0.0005000000819563866  │  4.427243915247421  │
│    4    │  '[master] 0 subscribed, 100 next'  │  0.003445461113855243  │ 0.0032989997416734695  │  0.006000000052154064  │ 1.8685515250963507  │
│    5    │    '[pr] 0 subscribed, 100 next'    │ 0.00044625133478185317 │  0.000499999150633812  │ 0.0009000003337860107  │ 0.6086487209661724  │
│    6    │   '[master] 1 subscribed, 1 next'   │ 0.0008947599909277633  │ 0.0010000001639127731  │ 0.0017999997362494469  │ 0.8469281728715339  │
│    7    │     '[pr] 1 subscribed, 1 next'     │ 0.0007666839421559125  │ 0.0007999995723366737  │ 0.0015000002458691597  │  0.462126717617466  │
│    8    │  '[master] 1 subscribed, 100 next'  │  0.004968361307883635  │  0.004700000397861004  │  0.009399999864399433  │ 0.3859075153627072  │
│    9    │    '[pr] 1 subscribed, 100 next'    │ 0.0013845615506991745  │  0.001300000585615635  │ 0.0027000000700354576  │ 0.8215533645812437  │
│   10    │   '[master] 3 subscribed, 1 next'   │ 0.0018689319399669765  │ 0.0017999997362494469  │ 0.0034999996423721313  │ 0.7049844808800837  │
│   11    │     '[pr] 3 subscribed, 1 next'     │ 0.0016349651360698045  │  0.001600000075995922  │  0.003100000321865082  │ 0.3527873535513193  │
│   12    │  '[master] 3 subscribed, 100 next'  │  0.008423075634939596  │  0.007800000719726086  │  0.01619999948889017   │ 0.29118011818976947 │
│   13    │    '[pr] 3 subscribed, 100 next'    │ 0.0030171170289674774  │  0.002900000661611557  │  0.005400000140070915  │ 0.47993844836563104 │
│   14    │  '[master] 10 subscribed, 1 next'   │  0.004465225901249796  │  0.004200000315904617  │  0.008200000040233135  │ 0.5787421444467985  │
│   15    │    '[pr] 10 subscribed, 1 next'     │  0.004932518482254818  │  0.004800000227987766  │  0.008999999612569809  │ 0.19471452904506512 │
│   16    │ '[master] 10 subscribed, 100 next'  │  0.02027628469098825   │  0.018200000748038292  │  0.040300000458955765  │ 0.5120671472684313  │
│   17    │   '[pr] 10 subscribed, 100 next'    │  0.008474460474032908  │  0.007999999448657036  │  0.01510000042617321   │ 0.2584698024940223  │
│   18    │  '[master] 100 subscribed, 1 next'  │   0.0368288599881772   │  0.03259999956935644   │  0.08150000032037497   │ 0.4215064656065205  │
│   19    │    '[pr] 100 subscribed, 1 next'    │  0.038937690858443265  │  0.03500000014901161   │  0.07730000000447035   │ 0.2287692086159684  │
│   20    │ '[master] 100 subscribed, 100 next' │  0.17048554184314701   │  0.15249900054186583   │  0.37639900017529726   │  0.159418273229607  │
│   21    │   '[pr] 100 subscribed, 100 next'   │  0.07705720384817198   │  0.06880000047385693   │   0.1596990004181862   │ 0.22773070779270208 │
└─────────┴─────────────────────────────────────┴────────────────────────┴────────────────────────┴────────────────────────┴─────────────────────┘

(before (mean) / after / (before divided by after))

  • Creating Subject: 0.00013759328511377957 / 0.00022728897428750432 / 0.6 🔴
  • 0 subscribed, 1 next: 0.000341275965122363 / 0.00019064141631205663 / 1.8 🟢
  • 0 subscribed, 100 next: 0.003445461113855243 / 0.00044625133478185317 / 7.7 🟢
  • 1 subscribed, 1 next: 0.0008947599909277633 / 0.0007666839421559125 / 1.2 🟢
  • 1 subscribed, 100 next: 0.004968361307883635 / 0.0013845615506991745 / 3.6 🟢
  • 3 subscribed, 1 next: 0.0018689319399669765 / 0.0016349651360698045 / 1.1 🟢
  • 3 subscribed, 100 next: 0.008423075634939596 / 0.0030171170289674774 / 2.8 🟢
  • 10 subscribed, 1 next: 0.004465225901249796 / 0.004932518482254818 / 0.9 🟠
  • 10 subscribed, 100 next: 0.02027628469098825 / 0.008474460474032908 / 2.4 🟢
  • 100 subscribed, 1 next: 0.0368288599881772 / 0.038937690858443265 / 0.9 🟠
  • 100 subscribed, 100 next: 0.17048554184314701 / 0.07705720384817198 / 2.2 🟢

@benlesh benlesh self-assigned this Apr 4, 2023
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refactor(Subject): some perf optimizations
1a6b91d 
+ Loops over indices of the observers array rather than creating a new iterator and using for-of for each emission
+ Removes unnecessary dirty boolean in favor of clearing the snapshot, which frees up memory a little
+ Centralizes observers list teardown and ensures it's called during `unsubscribe()`.
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dubzzz commented Apr 4, 2023

@benlesh do you want me to re-run the benchmarks following your changes?

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benlesh commented Apr 4, 2023 •
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@dubzzz I re-ran it, with some alterations. The more common case is that something will next thousands (or even millions) of times. Generally speaking, while subscription is a hot path, next is the "hottest" path in RxJS. The additional commit I added made about a 4x performance difference when dealing with 10,000 nexted values.

┌─────────┬───────────────────────────────────────────────┬────────────────────┬────────────────────┬────────────────────┬─────────────────────┐
│ (index) │                   Name                        │        Mean        │        P75         │        P99         │         RME         │
├─────────┼───────────────────────────────────────────────┼────────────────────┼────────────────────┼────────────────────┼─────────────────────┤
│    0    │ '[old commit] 1,000 subscribed, 10,000 next'  │ 103.60927042180597 │ 104.87890499830246 │ 117.56002202630043 │ 0.07193713572665707 │
│    1    │ '[new commit]  1,000 subscribed, 10,000 next' │ 25.604613090211153 │ 25.85596400499344  │ 28.47809898853302  │ 0.08366443995288589 │
└─────────┴───────────────────────────────────────────────┴────────────────────┴────────────────────┴────────────────────┴─────────────────────┘

┌─────────┬───────────────────────────────────────────┬─────────────────────┬─────────────────────┬─────────────────────┬────────────────────┐
│ (index) │                 Name                      │        Mean         │         P75         │         P99         │        RME         │
├─────────┼───────────────────────────────────────────┼─────────────────────┼─────────────────────┼─────────────────────┼────────────────────┤
│    0    │ '[old commit] 1 subscribed, 10,000 next'  │ 0.31226582655906676 │ 0.3486909866333008  │ 0.6682980060577393  │ 0.9511541628967262 │
│    1    │ '[new commit]  1 subscribed, 10,000 next' │ 0.07090659905672074 │ 0.08109098672866821 │ 0.12429198622703552 │ 0.7590550599162128 │
└─────────┴───────────────────────────────────────────┴─────────────────────┴─────────────────────┴─────────────────────┴────────────────────┘

@benlesh benlesh merged commit dbbae80 into ReactiveX:master Apr 4, 2023
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benlesh commented Apr 4, 2023

Thank you, @dubzzz

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dubzzz commented Apr 30, 2025

Hi @benlesh,

Just wondering if there is a chance to have this fix included into one stable release soon.
Maybe a back-port to 7.x versions?

Thanks in advance for your time

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