Add import of v8 heap allocation profile (#170)

This adds support for importing heap profiles from Chrome: https://developers.google.com/web/tools/chrome-devtools/memory-problems/#allocation-profile

src/import/index.ts

@@ -12,6 +12,7 @@ import {importFromLinuxPerf} from './linux-tools-perf'
 import {ProfileDataSource, TextProfileDataSource, MaybeCompressedDataReader} from './utils'
 import {importAsPprofProfile} from './pprof'
 import {decodeBase64} from '../lib/utils'
+import {importFromChromeHeapProfile} from './v8heapalloc'
 
 export async function importProfileGroupFromText(
   fileName: string,
@@ -103,6 +104,9 @@ async function _importProfileGroup(dataSource: ProfileDataSource): Promise<Profi
   } else if (fileName.endsWith('.v8log.json')) {
     console.log('Importing as --prof-process v8 log')
     return toGroup(importFromV8ProfLog(JSON.parse(contents)))
+  } else if (fileName.endsWith('.heapprofile')) {
+    console.log('Importing as Chrome Heap Profile')
+    return toGroup(importFromChromeHeapProfile(JSON.parse(contents)))
   }
 
   // Second pass: Try to guess what file format it is based on structure
@@ -129,6 +133,9 @@ async function _importProfileGroup(dataSource: ProfileDataSource): Promise<Profi
     } else if ('code' in parsed && 'functions' in parsed && 'ticks' in parsed) {
       console.log('Importing as --prof-process v8 log')
       return toGroup(importFromV8ProfLog(parsed))
+    } else if ('head' in parsed && 'selfSize' in parsed['head']) {
+      console.log('Importing as Chrome Heap Profile')
+      return toGroup(importFromChromeHeapProfile(JSON.parse(contents)))
     }
   } else {
     // Format is not JSON

src/import/v8heapalloc.test.ts

@@ -0,0 +1,9 @@
+import {checkProfileSnapshot} from '../lib/test-utils'
+
+test('importV8HeapAlloc from Chrome', async () => {
+  await checkProfileSnapshot('./sample/profiles/Chrome/69/Heap-20181005T144546.heapprofile')
+})
+
+test('importV8HeapAlloc from NodeJS', async () => {
+  await checkProfileSnapshot('./sample/profiles/node/10.11.0/Heap-20181003T105432.heapprofile')
+})

src/import/v8heapalloc.ts

@@ -0,0 +1,109 @@
+import {Profile, FrameInfo, StackListProfileBuilder} from '../lib/profile'
+import {getOrInsert} from '../lib/utils'
+import {ByteFormatter} from '../lib/value-formatters'
+
+/**
+ * The V8 Heap Allocation profile is a way to represent heap allocation for each
+ * javascript function. The format is a simple tree where the weight of each node
+ * represent the memory allocated by the function and all its callee.
+ * You can find more information on how to get a profile there :
+ * https://developers.google.com/web/tools/chrome-devtools/memory-problems/#allocation-profile
+ * You need to scroll down to "Investigate memory allocation by function"
+ *
+ * Note that Node.JS can retrieve this kind of profile via the Inspector protocol.
+ */
+
+interface HeapProfileCallFrame {
+  columnNumber: number
+  functionName: string
+  lineNumber: number
+  scriptId: string
+  url: string
+}
+
+interface HeapProfileNode {
+  callFrame: HeapProfileCallFrame
+  selfSize: number
+  children: HeapProfileNode[]
+  id: number
+  parent?: number
+  totalSize: number
+}
+
+interface HeapProfile {
+  head: HeapProfileNode
+}
+
+const callFrameToFrameInfo = new Map<HeapProfileCallFrame, FrameInfo>()
+function frameInfoForCallFrame(callFrame: HeapProfileCallFrame) {
+  return getOrInsert(callFrameToFrameInfo, callFrame, callFrame => {
+    const name = callFrame.functionName || '(anonymous)'
+    const file = callFrame.url
+    const line = callFrame.lineNumber
+    const col = callFrame.columnNumber
+    return {
+      key: `${name}:${file}:${line}:${col}`,
+      name,
+      file,
+      line,
+      col,
+    }
+  })
+}
+
+export function importFromChromeHeapProfile(chromeProfile: HeapProfile): Profile {
+  const nodeById = new Map<number, HeapProfileNode>()
+  let currentId = 0
+  const computeId = (node: HeapProfileNode, parent?: HeapProfileNode) => {
+    node.id = currentId++
+    nodeById.set(node.id, node)
+    if (parent) {
+      node.parent = parent.id
+    }
+
+    node.children.forEach(children => computeId(children, node))
+  }
+  computeId(chromeProfile.head)
+
+  // Compute the total size
+  const computeTotalSize = (node: HeapProfileNode): number => {
+    if (node.children.length === 0) return node.selfSize || 0
+    const totalChild = node.children.reduce((total: number, children) => {
+      total += computeTotalSize(children)
+      return total
+    }, node.selfSize)
+    node.totalSize = totalChild
+    return totalChild
+  }
+  const total = computeTotalSize(chromeProfile.head)
+
+  // Compute all stacks by taking each last node and going upward
+  const stacks: HeapProfileNode[][] = []
+  for (let currentNode of nodeById.values()) {
+    let stack: HeapProfileNode[] = []
+    stack.push(currentNode)
+    // While we found a parent
+    while (true) {
+      if (currentNode.parent === undefined) break
+      const parent = nodeById.get(currentNode.parent)
+      if (parent === undefined) break
+      // Push the parent at the beginning of the stack
+      stack.unshift(parent)
+      currentNode = parent
+    }
+    stacks.push(stack)
+  }
+
+  const profile = new StackListProfileBuilder(total)
+
+  for (let stack of stacks) {
+    const lastFrame = stack[stack.length - 1]
+    profile.appendSampleWithWeight(
+      stack.map(frame => frameInfoForCallFrame(frame.callFrame)),
+      lastFrame.selfSize,
+    )
+  }
+
+  profile.setValueFormatter(new ByteFormatter())
+  return profile.build()
+}