8237354: Add option to jcmd to write a gzipped heap dump

Reviewed-by: rrich, clanger, goetz

src/hotspot/share/gc/shared/workgroup.cpp

@@ -94,6 +94,17 @@ void AbstractWorkGang::threads_do(ThreadClosure* tc) const {
   }
 }
 
+static void run_foreground_task_if_needed(AbstractGangTask* task, uint num_workers,
+                                          bool add_foreground_work) {
+  if (add_foreground_work) {
+    log_develop_trace(gc, workgang)("Running work gang: %s task: %s worker: foreground",
+      Thread::current()->name(), task->name());
+    task->work(num_workers);
+    log_develop_trace(gc, workgang)("Finished work gang: %s task: %s worker: foreground "
+      "thread: " PTR_FORMAT, Thread::current()->name(), task->name(), p2i(Thread::current()));
+  }
+}
+
 // WorkGang dispatcher implemented with semaphores.
 //
 // Semaphores don't require the worker threads to re-claim the lock when they wake up.
@@ -124,14 +135,16 @@ class SemaphoreGangTaskDispatcher : public GangTaskDispatcher {
     delete _end_semaphore;
   }
 
-  void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) {
+  void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers, bool add_foreground_work) {
     // No workers are allowed to read the state variables until they have been signaled.
     _task         = task;
     _not_finished = num_workers;
 
     // Dispatch 'num_workers' number of tasks.
     _start_semaphore->signal(num_workers);
 
+    run_foreground_task_if_needed(task, num_workers, add_foreground_work);
+
     // Wait for the last worker to signal the coordinator.
     _end_semaphore->wait();
 
@@ -188,7 +201,7 @@ class MutexGangTaskDispatcher : public GangTaskDispatcher {
     delete _monitor;
   }
 
-  void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) {
+  void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers, bool add_foreground_work) {
     MonitorLocker ml(_monitor, Mutex::_no_safepoint_check_flag);
 
     _task        = task;
@@ -197,6 +210,8 @@ class MutexGangTaskDispatcher : public GangTaskDispatcher {
     // Tell the workers to get to work.
     _monitor->notify_all();
 
+    run_foreground_task_if_needed(task, num_workers, add_foreground_work);
+
     // Wait for them to finish.
     while (_finished < _num_workers) {
       ml.wait();
@@ -263,14 +278,14 @@ void WorkGang::run_task(AbstractGangTask* task) {
   run_task(task, active_workers());
 }
 
-void WorkGang::run_task(AbstractGangTask* task, uint num_workers) {
+void WorkGang::run_task(AbstractGangTask* task, uint num_workers, bool add_foreground_work) {
   guarantee(num_workers <= total_workers(),
             "Trying to execute task %s with %u workers which is more than the amount of total workers %u.",
             task->name(), num_workers, total_workers());
   guarantee(num_workers > 0, "Trying to execute task %s with zero workers", task->name());
   uint old_num_workers = _active_workers;
   update_active_workers(num_workers);
-  _dispatcher->coordinator_execute_on_workers(task, num_workers);
+  _dispatcher->coordinator_execute_on_workers(task, num_workers, add_foreground_work);
   update_active_workers(old_num_workers);
 }
 

src/hotspot/share/gc/shared/workgroup.hpp

@@ -90,7 +90,8 @@ class GangTaskDispatcher : public CHeapObj<mtGC> {
 
   // Distributes the task out to num_workers workers.
   // Returns when the task has been completed by all workers.
-  virtual void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) = 0;
+  virtual void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers,
+                                              bool add_foreground_work) = 0;
 
   // Worker API.
 
@@ -215,8 +216,9 @@ class WorkGang: public AbstractWorkGang {
   // Run a task with the given number of workers, returns
   // when the task is done. The number of workers must be at most the number of
   // active workers.  Additional workers may be created if an insufficient
-  // number currently exists.
-  void run_task(AbstractGangTask* task, uint num_workers);
+  // number currently exists. If the add_foreground_work flag is true, the current thread
+  // is used to run the task too.
+  void run_task(AbstractGangTask* task, uint num_workers, bool add_foreground_work = false);
 
 protected:
   virtual AbstractGangWorker* allocate_worker(uint which);

src/hotspot/share/services/diagnosticCommand.cpp

@@ -504,17 +504,32 @@ HeapDumpDCmd::HeapDumpDCmd(outputStream* output, bool heap) :
                            DCmdWithParser(output, heap),
   _filename("filename","Name of the dump file", "STRING",true),
   _all("-all", "Dump all objects, including unreachable objects",
-       "BOOLEAN", false, "false") {
+       "BOOLEAN", false, "false"),
+  _gzip("-gz", "If specified, the heap dump is written in gzipped format "
+               "using the given compression level. 1 (recommended) is the fastest, "
+               "9 the strongest compression.", "INT", false, "1") {
   _dcmdparser.add_dcmd_option(&_all);
   _dcmdparser.add_dcmd_argument(&_filename);
+  _dcmdparser.add_dcmd_option(&_gzip);
 }
 
 void HeapDumpDCmd::execute(DCmdSource source, TRAPS) {
+  jlong level = -1; // -1 means no compression.
+
+  if (_gzip.is_set()) {
+    level = _gzip.value();
+
+    if (level < 1 || level > 9) {
+      output()->print_cr("Compression level out of range (1-9): " JLONG_FORMAT, level);
+      return;
+    }
+  }
+
   // Request a full GC before heap dump if _all is false
   // This helps reduces the amount of unreachable objects in the dump
   // and makes it easier to browse.
   HeapDumper dumper(!_all.value() /* request GC if _all is false*/);
-  dumper.dump(_filename.value(), output());
+  dumper.dump(_filename.value(), output(), (int) level);
 }
 
 int HeapDumpDCmd::num_arguments() {

src/hotspot/share/services/diagnosticCommand.hpp

@@ -330,6 +330,7 @@ class HeapDumpDCmd : public DCmdWithParser {
 protected:
   DCmdArgument<char*> _filename;
   DCmdArgument<bool>  _all;
+  DCmdArgument<jlong> _gzip;
 public:
   HeapDumpDCmd(outputStream* output, bool heap);
   static const char* name() {