# HG changeset patch
# User jmasa
# Date 1463691590 25200
#      Thu May 19 13:59:50 2016 -0700
# Node ID 15b538bac28ee240135b3b62833cf2ce400ccfa7
# Parent  c31d418fc552c126515aab184025840544f7d8fe
[mq]: 8157240

diff --git a/src/share/vm/gc/parallel/gcTaskManager.cpp b/src/share/vm/gc/parallel/gcTaskManager.cpp
--- a/src/share/vm/gc/parallel/gcTaskManager.cpp
+++ b/src/share/vm/gc/parallel/gcTaskManager.cpp
@@ -386,6 +386,8 @@
 
 void GCTaskManager::add_workers(bool initializing) {
   os::ThreadType worker_type = os::pgc_thread;
+  uint previous_created_workers = _created_workers;
+
   _created_workers = WorkerManager::add_workers(this,
                                                 _active_workers,
                                                 (uint) _workers,
@@ -393,6 +395,16 @@
                                                 worker_type,
                                                 initializing);
   _active_workers = MIN2(_created_workers, _active_workers);
+
+  WorkerManager::log_worker_creation(this, previous_created_workers, _active_workers, _created_workers, initializing);
+}
+
+char *GCTaskManager::worker_name(uint which) {
+  if (thread(which) != NULL) {
+    return thread(which)->name();
+  } else {
+    return NULL;
+  }
 }
 
 void GCTaskManager::initialize() {
diff --git a/src/share/vm/gc/parallel/gcTaskManager.hpp b/src/share/vm/gc/parallel/gcTaskManager.hpp
--- a/src/share/vm/gc/parallel/gcTaskManager.hpp
+++ b/src/share/vm/gc/parallel/gcTaskManager.hpp
@@ -556,6 +556,8 @@
   GCTaskThread* install_worker(uint worker_id);
   // Add GC workers as needed.
   void add_workers(bool initializing);
+  // Return the thread name of a worker
+  char *worker_name(uint which);
 };
 
 //
diff --git a/src/share/vm/gc/shared/workerManager.hpp b/src/share/vm/gc/shared/workerManager.hpp
--- a/src/share/vm/gc/shared/workerManager.hpp
+++ b/src/share/vm/gc/shared/workerManager.hpp
@@ -67,11 +67,23 @@
       os::start_thread(new_worker);
     }
 
-    log_trace(gc, task)("AdaptiveSizePolicy::add_workers() : "
-       "active_workers: %u created_workers: %u",
-       active_workers, created_workers);
-
     return created_workers;
   }
+  
+  // Log (at trace level) a change in the number of created workers.
+  template <class WorkerType>
+  static void log_worker_creation(WorkerType* holder,
+                           uint previous_created_workers,
+                           uint active_workers,
+                           uint created_workers,
+                           bool initializing) {
+    if (previous_created_workers < created_workers) {
+      const char* initializing_msg =  initializing ? "Adding initial" : "";
+      log_trace(gc, task)("AdaptiveSizePolicy::add_workers() : %s "
+         "active_workers: %u created_workers: %u for %s to #%u",
+         initializing_msg, active_workers, created_workers,
+         holder->worker_name(previous_created_workers), created_workers - 1);
+    }
+  }
 };
 #endif // SHARE_VM_GC_SHARED_WORKERMANAGER_HPP
diff --git a/src/share/vm/gc/shared/workgroup.cpp b/src/share/vm/gc/shared/workgroup.cpp
--- a/src/share/vm/gc/shared/workgroup.cpp
+++ b/src/share/vm/gc/shared/workgroup.cpp
@@ -66,6 +66,7 @@
   } else {
     worker_type = os::pgc_thread;
   }
+  uint previous_created_workers = _created_workers;
 
   _created_workers = WorkerManager::add_workers(this,
                                                 active_workers,
@@ -74,6 +75,16 @@
                                                 worker_type,
                                                 initializing);
   _active_workers = MIN2(_created_workers, _active_workers);
+
+  WorkerManager::log_worker_creation(this, previous_created_workers, _active_workers, _created_workers, initializing);
+}
+
+char* AbstractWorkGang::worker_name(uint which) {
+  if (worker(which) != NULL) {
+    return worker(which)->name();
+  } else {
+    return NULL;
+  }
 }
 
 AbstractGangWorker* AbstractWorkGang::worker(uint i) const {
diff --git a/src/share/vm/gc/shared/workgroup.hpp b/src/share/vm/gc/shared/workgroup.hpp
--- a/src/share/vm/gc/shared/workgroup.hpp
+++ b/src/share/vm/gc/shared/workgroup.hpp
@@ -173,6 +173,9 @@
   // Add GC workers as needed to reach the specified number of workers.
   void add_workers(uint active_workers, bool initializing);
 
+  // Return the name of the thread in the work gang
+  char* worker_name(uint which);
+
   // Return the Ith worker.
   AbstractGangWorker* worker(uint i) const;