[inspector] avoid cloning of async call chains

src/inspector/v8-debugger.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/inspector/v8-debugger.h"
 
 #include "src/inspector/debugger-script.h"
 #include "src/inspector/inspected-context.h"
 #include "src/inspector/protocol/Protocol.h"
 #include "src/inspector/script-breakpoint.h"
 #include "src/inspector/string-util.h"
 #include "src/inspector/v8-debugger-agent-impl.h"
 #include "src/inspector/v8-inspector-impl.h"
 #include "src/inspector/v8-internal-value-type.h"
 #include "src/inspector/v8-stack-trace-impl.h"
 #include "src/inspector/v8-value-copier.h"
 
 #include "include/v8-util.h"
 
 namespace v8_inspector {
 
 namespace {
 
-// Based on DevTools frontend measurement, with asyncCallStackDepth = 4,
-// average async call stack tail requires ~1 Kb. Let's reserve ~ 128 Mb
-// for async stacks.
-static const int kMaxAsyncTaskStacks = 128 * 1024;
+static const int kMaxAsyncTaskStacks = 1024 * 1024;
 
 inline v8::Local<v8::Boolean> v8Boolean(bool value, v8::Isolate* isolate) {
   return value ? v8::True(isolate) : v8::False(isolate);
 }
 
 V8DebuggerAgentImpl* agentForScript(V8InspectorImpl* inspector,
                                     v8::Local<v8::debug::Script> script) {
   v8::Local<v8::Value> contextData;
   if (!script->ContextData().ToLocal(&contextData) || !contextData->IsInt32()) {
     return nullptr;
@@ skipping 122 matching lines @@
 }
 
 V8Debugger::V8Debugger(v8::Isolate* isolate, V8InspectorImpl* inspector)
     : m_isolate(isolate),
       m_inspector(inspector),
       m_enableCount(0),
       m_breakpointsActivated(true),
       m_runningNestedMessageLoop(false),
       m_ignoreScriptParsedEventsCounter(0),
       m_maxAsyncCallStacks(kMaxAsyncTaskStacks),
-      m_lastTaskId(0),
       m_maxAsyncCallStackDepth(0),
       m_pauseOnExceptionsState(v8::debug::NoBreakOnException),
       m_wasmTranslation(isolate) {}
 
 V8Debugger::~V8Debugger() {}
 
 void V8Debugger::enable() {
   if (m_enableCount++) return;
   DCHECK(!enabled());
   v8::HandleScope scope(m_isolate);
@@ skipping 461 matching lines @@
 
 void V8Debugger::PromiseEventOccurred(v8::Local<v8::Context> context,
                                       v8::debug::PromiseDebugActionType type,
                                       int id, int parentId,
                                       bool createdByUser) {
   // Async task events from Promises are given misaligned pointers to prevent
   // from overlapping with other Blink task identifiers.
   void* task = reinterpret_cast<void*>(id * 2 + 1);
   void* parentTask =
       parentId ? reinterpret_cast<void*>(parentId * 2 + 1) : nullptr;
+  if (type == v8::debug::kDebugPromiseCollected) {
+    asyncTaskCanceledForStack(task);
+    asyncTaskCanceledForStepping(task);
+    return;
+  }
+  v8::Context::Scope contextScope(context);

[dgozman, 2017/04/17 17:49:08]

Why new scope?

[kozy, 2017/04/17 21:34:17]

It wasn't new - moved from v8::debug::kDebugPromiseCreated. But the reason is we
enter debugger context before calling this delegate method on v8 side. I removed
this entering there and currently we don't need this scope at all :)

   switch (type) {
     case v8::debug::kDebugPromiseCreated:
       asyncTaskCreatedForStack(task, parentTask);
-      if (createdByUser && parentTask) {
-        v8::Context::Scope contextScope(context);
-        asyncTaskCandidateForStepping(task);
-      }
+      if (createdByUser && parentTask) asyncTaskCandidateForStepping(task);
       break;
     case v8::debug::kDebugEnqueueAsyncFunction:
       asyncTaskScheduledForStack("async function", task, true);
       break;
     case v8::debug::kDebugEnqueuePromiseResolve:
       asyncTaskScheduledForStack("Promise.resolve", task, true);
       break;
     case v8::debug::kDebugEnqueuePromiseReject:
       asyncTaskScheduledForStack("Promise.reject", task, true);
       break;
-    case v8::debug::kDebugPromiseCollected:
-      asyncTaskCanceledForStack(task);
-      asyncTaskCanceledForStepping(task);
-      break;
     case v8::debug::kDebugWillHandle:
       asyncTaskStartedForStack(task);
       asyncTaskStartedForStepping(task);
       break;
     case v8::debug::kDebugDidHandle:
       asyncTaskFinishedForStack(task);
       asyncTaskFinishedForStepping(task);
       break;
+    case v8::debug::kDebugPromiseCollected:
+      UNREACHABLE();
+      break;
   }
 }
 
-V8StackTraceImpl* V8Debugger::currentAsyncCallChain() {
-  if (!m_currentStacks.size()) return nullptr;
-  return m_currentStacks.back().get();
+std::shared_ptr<AsyncStackTrace> V8Debugger::currentAsyncParent() {
+  return m_currentAsyncParent.empty() ? nullptr : m_currentAsyncParent.back();
 }
 
-V8StackTraceImpl* V8Debugger::currentAsyncTaskCreationStack() {
-  if (!m_currentCreationStacks.size()) return nullptr;
-  return m_currentCreationStacks.back().get();
+std::shared_ptr<AsyncStackTrace> V8Debugger::currentAsyncCreation() {
+  return m_currentAsyncCreation.empty() ? nullptr
+                                        : m_currentAsyncCreation.back();
 }
 
 void V8Debugger::compileDebuggerScript() {
   if (!m_debuggerScript.IsEmpty()) {
     UNREACHABLE();
     return;
   }
 
   v8::HandleScope scope(m_isolate);
   v8::Context::Scope contextScope(debuggerContext());
@@ skipping 120 matching lines @@
         functionScopes(context, function).ToLocal(&scopes)) {
       createDataProperty(context, properties, properties->Length(),
                          toV8StringInternalized(m_isolate, "[[Scopes]]"));
       createDataProperty(context, properties, properties->Length(), scopes);
     }
   }
   return properties;
 }
 
 std::unique_ptr<V8StackTraceImpl> V8Debugger::createStackTrace(
-    v8::Local<v8::StackTrace> stackTrace) {
-  return V8StackTraceImpl::create(this, currentContextGroupId(), stackTrace,
+    v8::Local<v8::StackTrace> v8StackTrace) {
+  return V8StackTraceImpl::create(this, currentContextGroupId(), v8StackTrace,
                                   V8StackTraceImpl::maxCallStackSizeToCapture);
 }
 
 void V8Debugger::setAsyncCallStackDepth(V8DebuggerAgentImpl* agent, int depth) {
   if (depth <= 0)
     m_maxAsyncCallStackDepthMap.erase(agent);
   else
     m_maxAsyncCallStackDepthMap[agent] = depth;
 
   int maxAsyncCallStackDepth = 0;
   for (const auto& pair : m_maxAsyncCallStackDepthMap) {
     if (pair.second > maxAsyncCallStackDepth)
       maxAsyncCallStackDepth = pair.second;
   }
 
   if (m_maxAsyncCallStackDepth == maxAsyncCallStackDepth) return;
   m_maxAsyncCallStackDepth = maxAsyncCallStackDepth;
   if (!maxAsyncCallStackDepth) allAsyncTasksCanceled();
 }
 
-void V8Debugger::registerAsyncTaskIfNeeded(void* task) {
-  if (m_taskToId.find(task) != m_taskToId.end()) return;
-
-  int id = ++m_lastTaskId;
-  m_taskToId[task] = id;
-  m_idToTask[id] = task;
-  if (static_cast<int>(m_idToTask.size()) > m_maxAsyncCallStacks) {
-    void* taskToRemove = m_idToTask.begin()->second;
-    asyncTaskCanceledForStack(taskToRemove);
-  }
-}
-
 void V8Debugger::asyncTaskCreatedForStack(void* task, void* parentTask) {
   if (!m_maxAsyncCallStackDepth) return;
   if (parentTask) m_parentTask[task] = parentTask;
   v8::HandleScope scope(m_isolate);
-  // We don't need to pass context group id here because we get this callback
-  // from V8 for promise events only.
-  // Passing one as maxStackSize forces no async chain for the new stack and

[dgozman, 2017/04/17 17:49:08]

Leave this comment about passing one.

[kozy, 2017/04/17 21:34:17]

But it's not a true - we don't grow exponentially, I will left lighter version
of this comment.

-  // allows us to not grow exponentially.
-  std::unique_ptr<V8StackTraceImpl> creationStack =
-      V8StackTraceImpl::capture(this, 0, 1, String16());
-  if (creationStack && !creationStack->isEmpty()) {
-    m_asyncTaskCreationStacks[task] = std::move(creationStack);
-    registerAsyncTaskIfNeeded(task);
+  std::shared_ptr<AsyncStackTrace> asyncCreation =
+      AsyncStackTrace::capture(this, currentContextGroupId(), String16(), 1);
+  if (asyncCreation && !asyncCreation->isEmpty()) {
+    m_asyncTaskCreationStacks[task] = asyncCreation;
+    m_allAsyncStacks.push_back(asyncCreation);
+    ++m_asyncStacksCount;
+    collectOldAsyncStacksIfNeeded();
   }
 }
 
 void V8Debugger::asyncTaskScheduled(const StringView& taskName, void* task,
                                     bool recurring) {
   asyncTaskScheduledForStack(toString16(taskName), task, recurring);
   asyncTaskCandidateForStepping(task);
 }
 
 void V8Debugger::asyncTaskCanceled(void* task) {
   asyncTaskCanceledForStack(task);
   asyncTaskCanceledForStepping(task);
 }
 
 void V8Debugger::asyncTaskStarted(void* task) {
   asyncTaskStartedForStack(task);
   asyncTaskStartedForStepping(task);
 }
 
 void V8Debugger::asyncTaskFinished(void* task) {
   asyncTaskFinishedForStack(task);
   asyncTaskFinishedForStepping(task);
 }
 
 void V8Debugger::asyncTaskScheduledForStack(const String16& taskName,
                                             void* task, bool recurring) {
   if (!m_maxAsyncCallStackDepth) return;
   v8::HandleScope scope(m_isolate);
-  std::unique_ptr<V8StackTraceImpl> chain = V8StackTraceImpl::capture(
-      this, currentContextGroupId(),
-      V8StackTraceImpl::maxCallStackSizeToCapture, taskName);
+  std::shared_ptr<AsyncStackTrace> chain =

[dgozman, 2017/04/17 17:49:08]

nit: chain -> asyncStack

[kozy, 2017/04/17 21:34:17]

Done.

+      AsyncStackTrace::capture(this, currentContextGroupId(), taskName,
+                               V8StackTraceImpl::maxCallStackSizeToCapture);
   if (chain) {
-    m_asyncTaskStacks[task] = std::move(chain);
+    m_asyncTaskStacks[task] = chain;
     if (recurring) m_recurringTasks.insert(task);
-    registerAsyncTaskIfNeeded(task);
+
+    m_allAsyncStacks.push_back(chain);
+    ++m_asyncStacksCount;
+    collectOldAsyncStacksIfNeeded();
   }
 }
 
 void V8Debugger::asyncTaskCanceledForStack(void* task) {
   if (!m_maxAsyncCallStackDepth) return;
   m_asyncTaskStacks.erase(task);
   m_recurringTasks.erase(task);
   m_parentTask.erase(task);
   m_asyncTaskCreationStacks.erase(task);
-  auto it = m_taskToId.find(task);
-  if (it == m_taskToId.end()) return;
-  m_idToTask.erase(it->second);
-  m_taskToId.erase(it);
 }
 
 void V8Debugger::asyncTaskStartedForStack(void* task) {
   if (!m_maxAsyncCallStackDepth) return;
   m_currentTasks.push_back(task);
   auto parentIt = m_parentTask.find(task);
   AsyncTaskToStackTrace::iterator stackIt = m_asyncTaskStacks.find(
       parentIt == m_parentTask.end() ? task : parentIt->second);
   // Needs to support following order of events:
   // - asyncTaskScheduled
   //   <-- attached here -->
   // - asyncTaskStarted
   // - asyncTaskCanceled <-- canceled before finished
   //   <-- async stack requested here -->
   // - asyncTaskFinished
-  std::unique_ptr<V8StackTraceImpl> stack;
-  if (stackIt != m_asyncTaskStacks.end() && stackIt->second)
-    stack = stackIt->second->cloneImpl();
+  std::shared_ptr<AsyncStackTrace> asyncParent;
+  if (stackIt != m_asyncTaskStacks.end()) asyncParent = stackIt->second.lock();
   auto itCreation = m_asyncTaskCreationStacks.find(task);
-  if (stack && itCreation != m_asyncTaskCreationStacks.end()) {
-    m_currentCreationStacks.push_back(itCreation->second->cloneImpl());
+  if (asyncParent && itCreation != m_asyncTaskCreationStacks.end()) {
+    m_currentAsyncCreation.push_back(itCreation->second.lock());
   } else {
-    m_currentCreationStacks.push_back(nullptr);
+    m_currentAsyncCreation.push_back(nullptr);
   }
-  m_currentStacks.push_back(std::move(stack));
+  m_currentAsyncParent.push_back(asyncParent);
 }
 
 void V8Debugger::asyncTaskFinishedForStack(void* task) {
   if (!m_maxAsyncCallStackDepth) return;
   // We could start instrumenting half way and the stack is empty.
-  if (!m_currentStacks.size()) return;
+  if (!m_currentTasks.size()) return;
   DCHECK(m_currentTasks.back() == task);
   m_currentTasks.pop_back();
 
-  DCHECK(m_currentStacks.size() == m_currentCreationStacks.size());
-  m_currentStacks.pop_back();
-  m_currentCreationStacks.pop_back();
+  DCHECK(m_currentAsyncParent.size() == m_currentAsyncCreation.size());
+  m_currentAsyncParent.pop_back();
+  m_currentAsyncCreation.pop_back();
+
   if (m_recurringTasks.find(task) == m_recurringTasks.end()) {
     asyncTaskCanceledForStack(task);
   }
 }
 
 void V8Debugger::asyncTaskCandidateForStepping(void* task) {
   if (!m_stepIntoAsyncCallback) return;
   DCHECK(m_targetContextGroupId);
   if (currentContextGroupId() != m_targetContextGroupId) return;
   m_taskWithScheduledBreak = task;
@@ skipping 16 matching lines @@
 }
 
 void V8Debugger::asyncTaskCanceledForStepping(void* task) {
   if (task != m_taskWithScheduledBreak) return;
   m_taskWithScheduledBreak = nullptr;
 }
 
 void V8Debugger::allAsyncTasksCanceled() {
   m_asyncTaskStacks.clear();
   m_recurringTasks.clear();
-  m_currentStacks.clear();
-  m_currentCreationStacks.clear();
+  m_currentAsyncParent.clear();
+  m_currentAsyncCreation.clear();
   m_currentTasks.clear();
   m_parentTask.clear();
   m_asyncTaskCreationStacks.clear();
-  m_idToTask.clear();
-  m_taskToId.clear();
-  m_lastTaskId = 0;
+
+  m_allAsyncStacks.clear();
+  m_asyncStacksCount = 0;
 }
 
 void V8Debugger::muteScriptParsedEvents() {
   ++m_ignoreScriptParsedEventsCounter;
 }
 
 void V8Debugger::unmuteScriptParsedEvents() {
   --m_ignoreScriptParsedEventsCounter;
   DCHECK_GE(m_ignoreScriptParsedEventsCounter, 0);
 }
 
 std::unique_ptr<V8StackTraceImpl> V8Debugger::captureStackTrace(
     bool fullStack) {
   if (!m_isolate->InContext()) return nullptr;
 
   v8::HandleScope handles(m_isolate);
   int contextGroupId = currentContextGroupId();
   if (!contextGroupId) return nullptr;
 
-  size_t stackSize =
-      fullStack ? V8StackTraceImpl::maxCallStackSizeToCapture : 1;
-  if (m_inspector->enabledRuntimeAgentForGroup(contextGroupId))
+  int stackSize = 1;
+  if (fullStack || m_inspector->enabledRuntimeAgentForGroup(contextGroupId)) {
     stackSize = V8StackTraceImpl::maxCallStackSizeToCapture;
-
+  }
   return V8StackTraceImpl::capture(this, contextGroupId, stackSize);
 }
 
 int V8Debugger::currentContextGroupId() {
   if (!m_isolate->InContext()) return 0;
   return m_inspector->contextGroupId(m_isolate->GetCurrentContext());
 }
 
+void V8Debugger::collectOldAsyncStacksIfNeeded() {
+  if (m_asyncStacksCount < m_maxAsyncCallStacks) return;
+  while (m_asyncStacksCount > m_maxAsyncCallStacks / 2) {
+    m_allAsyncStacks.pop_front();
+    --m_asyncStacksCount;
+  }
+  removeOldAsyncTasks(m_asyncTaskStacks);
+  removeOldAsyncTasks(m_asyncTaskCreationStacks);
+}
+
+void V8Debugger::removeOldAsyncTasks(AsyncTaskToStackTrace& map) {
+  AsyncTaskToStackTrace cleanCopy;
+  for (auto it : map) {
+    if (!it.second.expired()) cleanCopy.insert(it);
+  }
+  map.swap(cleanCopy);
+}
+
+void V8Debugger::setMaxAsyncTaskStacksForTest(int limit) {
+  m_maxAsyncCallStacks = 0;
+  collectOldAsyncStacksIfNeeded();
+  m_maxAsyncCallStacks = limit;
+}
+
 }  // namespace v8_inspector