From: Evan You <evan@vuejs.org>
Date: Wed, 29 Jan 2025 07:53:20 +0000 (+0800)
Subject: perf: avoid now() overhead during dev measure calls
X-Git-Tag: v3.6.0-alpha.1~16^2~127
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e6ba91cface1dc9348b6d0bdb1293e00af4021a6;p=thirdparty%2Fvuejs%2Fcore.git

perf: avoid now() overhead during dev measure calls
---

diff --git a/packages/runtime-core/src/profiling.ts b/packages/runtime-core/src/profiling.ts
index ec789de721..c14207f91e 100644
--- a/packages/runtime-core/src/profiling.ts
+++ b/packages/runtime-core/src/profiling.ts
@@ -5,6 +5,15 @@ import { devtoolsPerfEnd, devtoolsPerfStart } from './devtools'
 let supported: boolean
 let perf: Performance
 
+// To avoid the overhead of repeatedly calling Date.now(), we cache
+// and use the same timestamp for all event listeners attached in the same tick.
+let cachedNow: number = 0
+const p = /*@__PURE__*/ Promise.resolve()
+const getNow = () =>
+  cachedNow ||
+  (p.then(() => (cachedNow = 0)),
+  (cachedNow = isSupported() ? perf.now() : Date.now()))
+
 /**
  * @internal
  */
@@ -17,7 +26,7 @@ export function startMeasure(
   }
 
   if (__DEV__ || __FEATURE_PROD_DEVTOOLS__) {
-    devtoolsPerfStart(instance, type, isSupported() ? perf.now() : Date.now())
+    devtoolsPerfStart(instance, type, getNow())
   }
 }
 
@@ -42,7 +51,7 @@ export function endMeasure(
   }
 
   if (__DEV__ || __FEATURE_PROD_DEVTOOLS__) {
-    devtoolsPerfEnd(instance, type, isSupported() ? perf.now() : Date.now())
+    devtoolsPerfEnd(instance, type, getNow())
   }
 }
 
diff --git a/packages/runtime-vapor/src/renderEffect.ts b/packages/runtime-vapor/src/renderEffect.ts
index 8b45b38226..0e4556fe1e 100644
--- a/packages/runtime-vapor/src/renderEffect.ts
+++ b/packages/runtime-vapor/src/renderEffect.ts
@@ -67,5 +67,4 @@ export function renderEffect(fn: () => void, noLifecycle = false): void {
   effect.run()
 
   // TODO recurse handling
-  // TODO measure
 }