From 73fbd61bd016eebbf2776dc94c15a26bf39668d6 Mon Sep 17 00:00:00 2001
From: snek <snek@deno.com>
Date: Fri, 8 Nov 2024 23:20:24 +0100
Subject: fix: performance.timeOrigin (#26787)

`performance.timeOrigin` was being set from when JS started executing,
but `op_now` measures from an `std::time::Instant` stored in `OpState`,
which is created at a completely different time. This caused
`performance.timeOrigin` to be very incorrect. This PR corrects the
origin and also cleans up some of the timer code.

Compared to `Date.now()`, `performance`'s time origin is now
consistently within 5us (0.005ms) of system time.


![image](https://github.com/user-attachments/assets/0a7be04a-4f6d-4816-bd25-38a2e6136926)
---
 ext/web/15_performance.js | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

(limited to 'ext/web/15_performance.js')

diff --git a/ext/web/15_performance.js b/ext/web/15_performance.js
index ea5557278..9e0e310a5 100644
--- a/ext/web/15_performance.js
+++ b/ext/web/15_performance.js
@@ -1,6 +1,7 @@
 // Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
 
 import { primordials } from "ext:core/mod.js";
+import { op_now, op_time_origin } from "ext:core/ops";
 const {
   ArrayPrototypeFilter,
   ArrayPrototypePush,
@@ -10,19 +11,34 @@ const {
   Symbol,
   SymbolFor,
   TypeError,
+  TypedArrayPrototypeGetBuffer,
+  Uint8Array,
+  Uint32Array,
 } = primordials;
 
 import * as webidl from "ext:deno_webidl/00_webidl.js";
 import { structuredClone } from "./02_structured_clone.js";
 import { createFilteredInspectProxy } from "ext:deno_console/01_console.js";
 import { EventTarget } from "./02_event.js";
-import { opNow } from "./02_timers.js";
 import { DOMException } from "./01_dom_exception.js";
 
 const illegalConstructorKey = Symbol("illegalConstructorKey");
 let performanceEntries = [];
 let timeOrigin;
 
+const hrU8 = new Uint8Array(8);
+const hr = new Uint32Array(TypedArrayPrototypeGetBuffer(hrU8));
+
+function setTimeOrigin() {
+  op_time_origin(hrU8);
+  timeOrigin = hr[0] * 1000 + hr[1] / 1e6;
+}
+
+function now() {
+  op_now(hrU8);
+  return hr[0] * 1000 + hr[1] / 1e6;
+}
+
 webidl.converters["PerformanceMarkOptions"] = webidl
   .createDictionaryConverter(
     "PerformanceMarkOptions",
@@ -90,10 +106,6 @@ webidl.converters["DOMString or PerformanceMeasureOptions"] = (
   return webidl.converters.DOMString(V, prefix, context, opts);
 };
 
-function setTimeOrigin(origin) {
-  timeOrigin = origin;
-}
-
 function findMostRecent(
   name,
   type,
@@ -135,8 +147,6 @@ function filterByNameType(
   );
 }
 
-const now = opNow;
-
 const _name = Symbol("[[name]]");
 const _entryType = Symbol("[[entryType]]");
 const _startTime = Symbol("[[startTime]]");
-- 
cgit v1.2.3