Add patch to fix accumulated negative deltas

jlfwong · Aug 4, 2020 · 9d892fc · 9d892fc
1 parent b26cdb5
commit 9d892fc
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Showing 2 changed files with 29 additions and 17 deletions.
diff --git a/src/import/__snapshots__/chrome.test.ts.snap b/src/import/__snapshots__/chrome.test.ts.snap
@@ -633,16 +633,16 @@ Object {
       "line": 0,
       "name": "(anonymous)",
       "selfWeight": 0,
-      "totalWeight": 2591,
+      "totalWeight": 2524,
     },
     Frame {
       "col": -1,
       "file": "",
       "key": "Worker::-1:-1",
       "line": -1,
       "name": "Worker",
-      "selfWeight": 873,
-      "totalWeight": 2591,
+      "selfWeight": 806,
+      "totalWeight": 2524,
     },
     Frame {
       "col": 29,
@@ -731,7 +731,7 @@ Object {
     "(program) 11.20ms",
     " 296.00µs",
     "(program) 1.90ms",
-    "(anonymous);Worker 873.00µs",
+    "(anonymous);Worker 806.00µs",
     "(anonymous);Worker;(program) 1.72ms",
     " 670.00µs",
     "(program) 28.45ms",
@@ -1305,7 +1305,7 @@ Object {
       "line": 0,
       "name": "(anonymous)",
       "selfWeight": 542,
-      "totalWeight": 6218,
+      "totalWeight": 6115,
     },
     Frame {
       "col": 25,
@@ -1314,16 +1314,16 @@ Object {
       "line": 30,
       "name": "insertTextScript",
       "selfWeight": 392,
-      "totalWeight": 977,
+      "totalWeight": 874,
     },
     Frame {
       "col": 25,
       "file": "chrome-extension://denbgaamihkadbghdceggmchnflmhpmk/contentScript.js",
       "key": "insertHeaderNode:chrome-extension://denbgaamihkadbghdceggmchnflmhpmk/contentScript.js:57:25",
       "line": 57,
       "name": "insertHeaderNode",
-      "selfWeight": 292,
-      "totalWeight": 585,
+      "selfWeight": 189,
+      "totalWeight": 482,
     },
     Frame {
       "col": undefined,
@@ -1558,7 +1558,7 @@ Object {
     "(anonymous);(anonymous);(anonymous);(program) 27.49ms",
     "(anonymous) 542.00µs",
     "(anonymous);insertTextScript 392.00µs",
-    "(anonymous);insertTextScript;insertHeaderNode 292.00µs",
+    "(anonymous);insertTextScript;insertHeaderNode 189.00µs",
     "(anonymous);insertTextScript;insertHeaderNode;appendChild;(anonymous);(anonymous) 148.00µs",
     "(anonymous);insertTextScript;insertHeaderNode;appendChild 145.00µs",
     "(anonymous);listenForMessage;get webstore 148.00µs",

diff --git a/src/import/chrome.ts b/src/import/chrome.ts
@@ -224,6 +224,9 @@ export function importFromChromeCPUProfile(chromeProfile: CPUProfile): Profile {
   // Ref: https://github.com/v8/v8/blob/44bd8fd7/src/inspector/js_protocol.json#L1485
   let elapsed = chromeProfile.timeDeltas[0]
 
+  // Prevents negative time deltas from causing bad data.
+  let lastElapsed = elapsed
+
   let lastNodeId = NaN
 
   // The chrome CPU profile format doesn't collapse identical samples. We'll do that
@@ -232,21 +235,30 @@ export function importFromChromeCPUProfile(chromeProfile: CPUProfile): Profile {
     const nodeId = chromeProfile.samples[i]
     if (nodeId != lastNodeId) {
       samples.push(nodeId)
-      sampleTimes.push(elapsed)
+      if (elapsed < lastElapsed) {
+        sampleTimes.push(lastElapsed)
+      } else {
+        sampleTimes.push(elapsed)
+        lastElapsed = elapsed
+      }
     }
 
     if (i === chromeProfile.samples.length - 1) {
       if (!isNaN(lastNodeId)) {
         samples.push(lastNodeId)
-        sampleTimes.push(elapsed)
+        if (elapsed < lastElapsed) {
+          sampleTimes.push(lastElapsed)
+        } else {
+          sampleTimes.push(elapsed)
+          lastElapsed = elapsed
+        }
       }
     } else {
-      let timeDelta = chromeProfile.timeDeltas[i + 1]
-      if (timeDelta < 0) {
-        // This is super noisy, but can be helpful when debugging strange data
-        // console.warn('Substituting zero for unexpected time delta:', timeDelta, 'at index', i)
-        timeDelta = 0
-      }
+      const timeDelta = chromeProfile.timeDeltas[i + 1]
+      // This is super noisy, but can be helpful when debugging strange data
+      // if (timeDelta < 0) {
+      //   console.warn('Substituting zero for unexpected time delta:', timeDelta, 'at index', i)
+      // }
 
       elapsed += timeDelta
       lastNodeId = nodeId