Repository: denoland/deno
Pull request: perf(ext/web): optimize performance.measure()

This PR optimizes the case when `performance.measure()` needs to find the startMark by name. It is a simple change on `findMostRecent` fn to avoiding copying and reversing the complete entries list.

Adds minor missing tests for:
- `clearMarks()`, general
- `clearMeasures()`, general
- `measure()`, case when the startMarks name exists more than once

### Benchmarks

#### main

```
    CPU | AMD Ryzen 7 PRO 6850U with Radeon Graphics
Runtime | Deno 2.0.0-rc.4 (x86_64-unknown-linux-gnu)

benchmark              time/iter (avg)        iter/s      (min … max)           p75      p99     p995
---------------------- ----------------------------- --------------------- --------------------------
worst case measure()            2.1 ms         486.9 (  1.7 ms …   2.4 ms)   2.2 ms   2.4 ms   2.4 ms
```

#### this PR

```
    CPU | AMD Ryzen 7 PRO 6850U with Radeon Graphics
Runtime | Deno 2.0.0-rc.4 (x86_64-unknown-linux-gnu)

benchmark              time/iter (avg)        iter/s      (min … max)           p75      p99     p995
---------------------- ----------------------------- --------------------- --------------------------
worst case measure()          966.3 µs         1,035 (876.9 µs …   1.1 ms)   1.0 ms   1.1 ms   1.1 ms
```

```ts
Deno.bench("worst case measure()", (b) => {
  performance.mark('start');

  for (let i = 0; i < 1e5; i += 1) {
    performance.mark(crypto.randomUUID());
  }

  b.start();

  performance.measure('total', 'start');

  b.end();

  performance.clearMarks();
  performance.clearMeasures();
});
```


Changed files:
filename: ext/web/15_performance.js
patch: @@ -3,10 +3,7 @@
 import { primordials } from "ext:core/mod.js";
 const {
   ArrayPrototypeFilter,
-  ArrayPrototypeFind,
   ArrayPrototypePush,
-  ArrayPrototypeReverse,
-  ArrayPrototypeSlice,
   ObjectKeys,
   ObjectPrototypeIsPrototypeOf,
   ReflectHas,
@@ -101,10 +98,12 @@ function findMostRecent(
   name,
   type,
 ) {
-  return ArrayPrototypeFind(
-    ArrayPrototypeReverse(ArrayPrototypeSlice(performanceEntries)),
-    (entry) => entry.name === name && entry.entryType === type,
-  );
+  for (let i = performanceEntries.length - 1; i >= 0; --i) {
+    const entry = performanceEntries[i];
+    if (entry.name === name && entry.entryType === type) {
+      return entry;
+    }
+  }
 }
 
 function convertMarkToTimestamp(mark) {

filename: tests/unit/performance_test.ts
patch: @@ -2,6 +2,7 @@
 import {
   assert,
   assertEquals,
+  assertNotEquals,
   assertNotStrictEquals,
   assertStringIncludes,
   assertThrows,
@@ -36,6 +37,41 @@ Deno.test(function performanceToJSON() {
   assertEquals(Object.keys(json).length, 1);
 });
 
+Deno.test(function clearMarks() {
+  performance.mark("a");
+  performance.mark("a");
+  performance.mark("b");
+  performance.mark("c");
+
+  const marksNum = performance.getEntriesByType("mark").length;
+
+  performance.clearMarks("a");
+  assertEquals(performance.getEntriesByType("mark").length, marksNum - 2);
+
+  performance.clearMarks();
+  assertEquals(performance.getEntriesByType("mark").length, 0);
+});
+
+Deno.test(function clearMeasures() {
+  performance.measure("from-start");
+  performance.mark("a");
+  performance.measure("from-mark-a", "a");
+  performance.measure("from-start");
+  performance.measure("from-mark-a", "a");
+  performance.mark("b");
+  performance.measure("between-a-and-b", "a", "b");
+
+  const measuresNum = performance.getEntriesByType("measure").length;
+
+  performance.clearMeasures("from-start");
+  assertEquals(performance.getEntriesByType("measure").length, measuresNum - 2);
+
+  performance.clearMeasures();
+  assertEquals(performance.getEntriesByType("measure").length, 0);
+
+  performance.clearMarks();
+});
+
 Deno.test(function performanceMark() {
   const mark = performance.mark("test");
   assert(mark instanceof PerformanceMark);
@@ -127,6 +163,25 @@ Deno.test(function performanceMeasure() {
   });
 });
 
+Deno.test(function performanceMeasureUseMostRecentMark() {
+  const markName1 = "mark1";
+  const measureName1 = "measure1";
+  const mark1 = performance.mark(markName1);
+  return new Promise((resolve, reject) => {
+    setTimeout(() => {
+      try {
+        const laterMark1 = performance.mark(markName1);
+        const measure1 = performance.measure(measureName1, markName1);
+        assertNotEquals(mark1.startTime, measure1.startTime);
+        assertEquals(laterMark1.startTime, measure1.startTime);
+      } catch (e) {
+        return reject(e);
+      }
+      resolve();
+    }, 100);
+  });
+});
+
 Deno.test(function performanceCustomInspectFunction() {
   assertStringIncludes(Deno.inspect(performance), "Performance");
   assertStringIncludes(