Switch profiler from isolates to threads

runtime/vm/thread_interrupter.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/thread_interrupter.h"
 
 #include "vm/flags.h"
 #include "vm/lockers.h"
 #include "vm/os.h"
 #include "vm/simulator.h"
@@ skipping 33 matching lines @@
 // thread local storage pointer is set again. This has an important side
 // effect: if the thread is interrupted by a signal handler during a ThreadState
 // update the signal handler will immediately return.
 
 DEFINE_FLAG(bool, trace_thread_interrupter, false,
             "Trace thread interrupter");
 
 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;
 intptr_t ThreadInterrupter::interrupt_period_ = 1000;
 intptr_t ThreadInterrupter::current_wait_time_ = Monitor::kNoTimeout;
 
 
 void ThreadInterrupter::InitOnce() {
   ASSERT(!initialized_);
   monitor_ = new Monitor();
@@ skipping 52 matching lines @@
 void ThreadInterrupter::SetInterruptPeriod(intptr_t period) {
   if (shutdown_) {
     return;
   }
   ASSERT(initialized_);
   ASSERT(period > 0);
   interrupt_period_ = 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;
     }
     // Notify the interrupter to wake it from its deep sleep.
     ml.Notify();
   }
 }
 
 
-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();
   if (FLAG_trace_thread_interrupter) {
     OS::Print("ThreadInterrupter thread running.\n");
   }
   {
     // Signal to main thread we are ready.
     MonitorLocker startup_ml(monitor_);
     interrupter_thread_id_ = OSThread::GetCurrentThreadJoinId();
     thread_running_ = true;
     startup_ml.Notify();
   }
   {
-    ThreadInterrupterVisitIsolates visitor;
+    intptr_t interrupted_thread_count = 0;
     current_wait_time_ = interrupt_period_;
     MonitorLocker wait_ml(monitor_);
     while (!shutdown_) {
       intptr_t r = wait_ml.WaitMicros(current_wait_time_);
 
       if ((r == Monitor::kNotified) && shutdown_) {

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

Shouldn't we break out of the loop regardless whether we were notified or timed
out?

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

Done.

         break;
       }
 
       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;
 
-      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.
+      // 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 (!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;
       }
 
       ASSERT(current_wait_time_ != Monitor::kNoTimeout);
     }
   }
   RemoveSignalHandler();
   if (FLAG_trace_thread_interrupter) {
     OS::Print("ThreadInterrupter thread exiting.\n");
   }
   {
     // Signal to main thread we are exiting.
     MonitorLocker shutdown_ml(monitor_);
     thread_running_ = false;
     shutdown_ml.Notify();
   }
 }
 
 }  // namespace dart