From fe2899c2acabd2262f8b9c6230e821192ea369e3 Mon Sep 17 00:00:00 2001
From: Eli Barzilay <eli@barzilay.org>
Date: Mon, 8 Feb 2021 15:54:35 -0500
Subject: [PATCH] Use a 10ms sampling frequency to filter tracing dumps

Currently hard-wired to 10ms, can be made configurable if needed later.
---
 src/compiler/tracing.ts | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/compiler/tracing.ts b/src/compiler/tracing.ts
index 41d7c8508e3..87c2abf4f48 100644
--- a/src/compiler/tracing.ts
+++ b/src/compiler/tracing.ts
@@ -140,12 +140,15 @@ namespace ts.tracingEnabled { // eslint-disable-line one-namespace-per-file
         }
         eventStack.length = 0;
     }
+    // sample every 10ms
+    const sampleInterval = 1000 * 10;
     function writeStackEvent(index: number, endTime: number) {
         const { phase, name, args, time, separateBeginAndEnd } = eventStack[index];
         if (separateBeginAndEnd) {
             writeEvent("E", phase, name, args, /*extras*/ undefined, endTime);
         }
-        else {
+        // test if [time,endTime) straddles a sampling point
+        else if (sampleInterval - (time % sampleInterval) <= endTime - time) {
             writeEvent("X", phase, name, args, `"dur":${endTime - time}`, time);
         }
     }