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 106 matching lines @@
   if (shutdown_) {
     return;
   }
   ASSERT(initialized_);
   ASSERT(period > 0);
   interrupt_period_ = period;
 }
 
 
 void ThreadInterrupter::WakeUp() {
+  if (!initialized_) {
+    // Early call.
+    return;
+  }
   ASSERT(initialized_);
   {
     MonitorLocker ml(monitor_);
     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) {
   // 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_) {
         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;
 

[siva, 2015/10/26 23:45:26]

Do we need to be holding the monitor_ lock here, we have only one interrupter
thread right so access and updates of variable current_wait_time_ should be
safe.

I am just trying to see if we can avoid the nesting of locks here as
ThreadIterator will be taking the global lock Thread::thread_list_lock_. (Will
keep the code simpler)

[Cutch, 2015/10/27 22:36:24]

Done.

-      if (visitor.profiled_thread_count() == 0) {
-        // No isolates were profiled. In order to reduce unnecessary CPU
+      {
+        ThreadIterator it;
+        while (it.HasNext()) {
+          Thread* thread = it.Next();
+          if (thread->ThreadInterruptsEnabled()) {
+            interrupted_thread_count++;
+            InterruptThread(thread);
+          }
+        }
+      }
+
+      if (interrupted_thread_count == 0) {
+        // No threads were interrupted. 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