src/share/vm/runtime/synchronizer.cpp

rev 13053 : 8180932: Parallelize safepoint cleanup
Summary: Provide infrastructure to do safepoint cleanup tasks using parallel worker threads
Reviewed-by: dholmes, rehn

*** 1693,1713 ****
    // And in case the vm thread is acquiring a lock during a safepoint
    // See e.g. 6320749
    Thread::muxAcquire(&gListLock, "scavenge - return");
  
    if (MonitorInUseLists) {
!     int inUse = 0;
!     for (JavaThread* cur = Threads::first(); cur != NULL; cur = cur->next()) {
!       nInCirculation+= cur->omInUseCount;
!       int deflated_count = deflate_monitor_list(cur->omInUseList_addr(), &freeHeadp, &freeTailp);
!       cur->omInUseCount-= deflated_count;
!       if (ObjectMonitor::Knob_VerifyInUse) {
!         verifyInUse(cur);
!       }
!       nScavenged += deflated_count;
!       nInuse += cur->omInUseCount;
!     }
  
      // For moribund threads, scan gOmInUseList
      if (gOmInUseList) {
        nInCirculation += gOmInUseCount;
        int deflated_count = deflate_monitor_list((ObjectMonitor **)&gOmInUseList, &freeHeadp, &freeTailp);
--- 1693,1704 ----
    // And in case the vm thread is acquiring a lock during a safepoint
    // See e.g. 6320749
    Thread::muxAcquire(&gListLock, "scavenge - return");
  
    if (MonitorInUseLists) {
!     // Note: the thread-local monitors lists get deflated in
!     // a separate pass. See deflate_thread_local_monitors().
  
      // For moribund threads, scan gOmInUseList
      if (gOmInUseList) {
        nInCirculation += gOmInUseCount;
        int deflated_count = deflate_monitor_list((ObjectMonitor **)&gOmInUseList, &freeHeadp, &freeTailp);
*** 1778,1787 ****
--- 1769,1805 ----
    // Audit/inventory the objectMonitors -- make sure they're all accounted for.
    GVars.stwRandom = os::random();
    GVars.stwCycle++;
  }
  
+ void ObjectSynchronizer::deflate_thread_local_monitors(Thread* thread) {
+   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+   if (! MonitorInUseLists) return;
+ 
+   ObjectMonitor * freeHeadp = NULL;  // Local SLL of scavenged monitors
+   ObjectMonitor * freeTailp = NULL;
+ 
+   int deflated_count = deflate_monitor_list(thread->omInUseList_addr(), &freeHeadp, &freeTailp);
+   thread->omInUseCount-= deflated_count;
+   if (ObjectMonitor::Knob_VerifyInUse) {
+     verifyInUse(thread);
+   }
+ 
+   // Move the scavenged monitors back to the global free list.
+   if (freeHeadp != NULL) {
+     Thread::muxAcquire(&gListLock, "scavenge - return");
+     guarantee(freeTailp != NULL && deflated_count > 0, "invariant");
+     assert(freeTailp->FreeNext == NULL, "invariant");
+ 
+     gMonitorFreeCount += deflated_count;
+     // constant-time list splice - prepend scavenged segment to gFreeList
+     freeTailp->FreeNext = gFreeList;
+     gFreeList = freeHeadp;
+     Thread::muxRelease(&gListLock);
+   }
+ }
+ 
  // Monitor cleanup on JavaThread::exit
  
  // Iterate through monitor cache and attempt to release thread's monitors
  // Gives up on a particular monitor if an exception occurs, but continues
  // the overall iteration, swallowing the exception.