Bug 1643170, part 2 - Report memory for HelperThreads::helperContexts_. r=jandem

This is 41600 bytes of unreported memory in each process.

Differential Revision: https://phabricator.services.mozilla.com/D78813

js/public/MemoryMetrics.h

@@ -452,7 +452,8 @@ struct HelperThreadStats {
   MACRO(_, MallocHeap, stateData)      \
   MACRO(_, MallocHeap, parseTask)      \
   MACRO(_, MallocHeap, ionCompileTask) \
-  MACRO(_, MallocHeap, wasmCompile)
+  MACRO(_, MallocHeap, wasmCompile)    \
+  MACRO(_, MallocHeap, contexts)
 
   HelperThreadStats() = default;
 

js/src/vm/HelperThreads.cpp

@@ -1428,7 +1428,8 @@ void GlobalHelperThreadState::addSizeOfIncludingThis(
       compressionPendingList_.sizeOfExcludingThis(mallocSizeOf) +
       compressionWorklist_.sizeOfExcludingThis(mallocSizeOf) +
       compressionFinishedList_.sizeOfExcludingThis(mallocSizeOf) +
-      gcParallelWorklist_.sizeOfExcludingThis(mallocSizeOf);
+      gcParallelWorklist_.sizeOfExcludingThis(mallocSizeOf) +
+      helperContexts_.sizeOfExcludingThis(mallocSizeOf);
 
   // Report ParseTasks on wait lists
   for (auto task : parseWorklist_) {
@@ -1460,6 +1461,17 @@ void GlobalHelperThreadState::addSizeOfIncludingThis(
     htStats.wasmCompile += task->sizeOfExcludingThis(mallocSizeOf);
   }
 
+  {
+    // Report memory used by the JSContexts.
+    // We're holding the helper state lock, and the JSContext memory reporter
+    // won't do anything more substantial than traversing data structures and
+    // getting their size, so disable ProtectedData checks.
+    AutoNoteSingleThreadedRegion anstr;
+    for (auto* cx : helperContexts_) {
+      htStats.contexts += cx->sizeOfIncludingThis(mallocSizeOf);
+    }
+  }
+
   // Report number of helper threads.
   MOZ_ASSERT(htStats.idleThreadCount == 0);
   if (threads) {

js/xpconnect/src/XPCJSRuntime.cpp

@@ -2555,6 +2555,11 @@ void JSReporter::CollectReports(WindowPaths* windowPaths,
       NS_LITERAL_CSTRING("explicit/js-non-window/helper-thread/wasm-compile"),
       KIND_HEAP, gStats.helperThread.wasmCompile,
       "The memory used by Wasm compilations waiting in HelperThreadState.");
+
+  REPORT_BYTES(
+      NS_LITERAL_CSTRING("explicit/js-non-window/helper-thread/contexts"),
+      KIND_HEAP, gStats.helperThread.contexts,
+      "The memory used by the JSContexts in HelperThreadState.");
 }
 
 static nsresult JSSizeOfTab(JSObject* objArg, size_t* jsObjectsSize,