Switch profiler from isolates to threads

runtime/vm/thread_interrupter.cc

Index: runtime/vm/thread_interrupter.cc
diff --git a/runtime/vm/thread_interrupter.cc b/runtime/vm/thread_interrupter.cc
index 58c94bec797cc04dadc697d31c33db8dd7d31f8e..a151791963c754d932214626eca594ab47f04cc0 100644
--- a/runtime/vm/thread_interrupter.cc
+++ b/runtime/vm/thread_interrupter.cc
@@ -51,6 +51,7 @@ DEFINE_FLAG(bool, trace_thread_interrupter, false,
 bool ThreadInterrupter::initialized_ = false;
 bool ThreadInterrupter::shutdown_ = false;
 bool ThreadInterrupter::thread_running_ = false;
+bool ThreadInterrupter::woken_up_ = false;
 ThreadJoinId ThreadInterrupter::interrupter_thread_id_ =
     OSThread::kInvalidThreadJoinId;
 Monitor* ThreadInterrupter::monitor_ = NULL;
@@ -124,9 +125,14 @@ void ThreadInterrupter::SetInterruptPeriod(intptr_t period) {
 
 
 void ThreadInterrupter::WakeUp() {

[Ivan Posva, 2015/10/28 08:27:47]

It is not clear to me from this CL when the ThreadInterrupter is being woken up.
Obviously when a new thread is created and added to the list of threads and when
the API marks a thread as unblocked. But in regular message handler execution?

+  if (!initialized_) {
+    // Early call.
+    return;
+  }
   ASSERT(initialized_);
   {
     MonitorLocker ml(monitor_);
+    woken_up_ = true;
     if (!InDeepSleep()) {
       // No need to notify, regularly waking up.
       return;
@@ -137,35 +143,11 @@ void ThreadInterrupter::WakeUp() {
 }
 
 
-void ThreadInterruptNoOp(const InterruptedThreadState& state, void* data) {
+void ThreadInterruptNoOp(Thread* thread, const InterruptedThreadState& state) {

[Ivan Posva, 2015/10/28 08:27:47]

Where is this used?

[Cutch, 2015/10/28 14:39:19]

Nowhere. It's gone now.

   // NoOp.
 }
 
 
-class ThreadInterrupterVisitIsolates : public IsolateVisitor {
- public:
-  ThreadInterrupterVisitIsolates() {
-    profiled_thread_count_ = 0;
-  }
-
-  void VisitIsolate(Isolate* isolate) {
-    ASSERT(isolate != NULL);
-    profiled_thread_count_ += isolate->ProfileInterrupt();
-  }
-
-  intptr_t profiled_thread_count() const {
-    return profiled_thread_count_;
-  }
-
-  void set_profiled_thread_count(intptr_t profiled_thread_count) {
-    profiled_thread_count_ = profiled_thread_count;
-  }
-
- private:
-  intptr_t profiled_thread_count_;
-};
-
-
 void ThreadInterrupter::ThreadMain(uword parameters) {
   ASSERT(initialized_);
   InstallSignalHandler();
@@ -180,7 +162,7 @@ void ThreadInterrupter::ThreadMain(uword parameters) {
     startup_ml.Notify();
   }
   {
-    ThreadInterrupterVisitIsolates visitor;
+    intptr_t interrupted_thread_count = 0;
     current_wait_time_ = interrupt_period_;
     MonitorLocker wait_ml(monitor_);
     while (!shutdown_) {
@@ -192,19 +174,41 @@ void ThreadInterrupter::ThreadMain(uword parameters) {
 
       if ((r == Monitor::kNotified) && InDeepSleep()) {
         // Woken up from deep sleep.
-        ASSERT(visitor.profiled_thread_count() == 0);
+        ASSERT(interrupted_thread_count == 0);
         // Return to regular interrupts.
         current_wait_time_ = interrupt_period_;
       }
 
-      // Reset count before visiting isolates.
-      visitor.set_profiled_thread_count(0);
-      Isolate::VisitIsolates(&visitor);
+      // Reset count before interrupting any threads.
+      interrupted_thread_count = 0;
+
+      // Temporarily drop the monitor while we interrupt threads.
+      monitor_->Exit();
+
+      {
+        ThreadIterator it;
+        while (it.HasNext()) {
+          Thread* thread = it.Next();
+          if (thread->ThreadInterruptsEnabled()) {
+            interrupted_thread_count++;
+            InterruptThread(thread);
+          }
+        }
+      }
+
+      // Take the monitor lock again.
+      monitor_->Enter();
+
+      // Now that we have the lock, check if we were signal to wake up while
+      // interrupting threads.
+      const bool woken_up = woken_up_;
+      // Clear the state.
+      woken_up_ = false;
 
-      if (visitor.profiled_thread_count() == 0) {
-        // No isolates were profiled. In order to reduce unnecessary CPU
-        // load, we will wait until we are notified before attempting to
-        // interrupt again.
+      if (!woken_up && (interrupted_thread_count == 0)) {
+        // No threads were interrupted and we were not signaled to interrupt
+        // new threads. In order to reduce unnecessary CPU load, we will wait
+        // until we are notified before attempting to interrupt again.
         current_wait_time_ = Monitor::kNoTimeout;
         continue;
       }