src/hotspot/share/gc/z/zHeap.cpp

Concurrent class unloading

*** 20,37 ****
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  #include "precompiled.hpp"
  #include "gc/shared/oopStorage.hpp"
  #include "gc/z/zAddress.hpp"
- #include "gc/z/zGlobals.hpp"
  #include "gc/z/zHeap.inline.hpp"
  #include "gc/z/zHeapIterator.hpp"
  #include "gc/z/zList.inline.hpp"
  #include "gc/z/zLock.inline.hpp"
  #include "gc/z/zMark.inline.hpp"
  #include "gc/z/zOopClosures.inline.hpp"
  #include "gc/z/zPage.inline.hpp"
  #include "gc/z/zPageTable.inline.hpp"
  #include "gc/z/zRelocationSet.inline.hpp"
  #include "gc/z/zResurrection.hpp"
--- 20,38 ----
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  #include "precompiled.hpp"
+ #include "code/codeCache.hpp"
  #include "gc/shared/oopStorage.hpp"
  #include "gc/z/zAddress.hpp"
  #include "gc/z/zHeap.inline.hpp"
  #include "gc/z/zHeapIterator.hpp"
  #include "gc/z/zList.inline.hpp"
  #include "gc/z/zLock.inline.hpp"
  #include "gc/z/zMark.inline.hpp"
+ #include "gc/z/zNMethodTable.hpp"
  #include "gc/z/zOopClosures.inline.hpp"
  #include "gc/z/zPage.inline.hpp"
  #include "gc/z/zPageTable.inline.hpp"
  #include "gc/z/zRelocationSet.inline.hpp"
  #include "gc/z/zResurrection.hpp"
***************
*** 340,362 ****
    }
  
    // Enter mark completed phase
    ZGlobalPhase = ZPhaseMarkCompleted;
  
-   // Resize metaspace
-   MetaspaceGC::compute_new_size();
- 
    // Update statistics
    ZStatSample(ZSamplerHeapUsedAfterMark, used());
    ZStatHeap::set_at_mark_end(capacity(), allocated(), used());
  
    // Block resurrection of weak/phantom references
    ZResurrection::block();
  
    // Process weak roots
    _weak_roots_processor.process_weak_roots();
  
    // Verification
    if (VerifyBeforeGC || VerifyDuringGC || VerifyAfterGC) {
      Universe::verify();
    }
  
--- 341,364 ----
    }
  
    // Enter mark completed phase
    ZGlobalPhase = ZPhaseMarkCompleted;
  
    // Update statistics
    ZStatSample(ZSamplerHeapUsedAfterMark, used());
    ZStatHeap::set_at_mark_end(capacity(), allocated(), used());
  
    // Block resurrection of weak/phantom references
    ZResurrection::block();
  
    // Process weak roots
    _weak_roots_processor.process_weak_roots();
  
+   if (ClassUnloading) {
+     CodeCache::increment_unloading_cycle();
+   }
+ 
    // Verification
    if (VerifyBeforeGC || VerifyDuringGC || VerifyAfterGC) {
      Universe::verify();
    }
  
***************
*** 365,381 ****
--- 367,422 ----
  
  void ZHeap::set_soft_reference_policy(bool clear) {
    _reference_processor.set_soft_reference_policy(clear);
  }
  
+ class ZNoOpHandshakeClosure : public ThreadClosure {
+ public:
+   void do_thread(Thread* thread) { }
+ };
+ 
+ void ZHeap::mutator_rendezvous() {
+   ZNoOpHandshakeClosure cl;
+   Handshake::execute(&cl);
+ }
+ 
  void ZHeap::process_non_strong_references() {
    // Process Soft/Weak/Final/PhantomReferences
    _reference_processor.process_references();
  
    // Process concurrent weak roots
    _weak_roots_processor.process_concurrent_weak_roots();
  
+   if (ClassUnloading) {
+     {
+       // 1. This is the unlinking phase; remove references to stale metadata and nmethods
+       ZPhantomIsAliveObjectClosure is_alive;
+ 
+       // Unlink the classes.
+       bool unloading_occurred = SystemDictionary::do_unloading(ZStatPhase::timer(), true /* do_cleaning */);
+ 
+       // Unload the nmethods.
+       ZNMethodTable::do_unloading(&_workers, &is_alive, unloading_occurred);
+ 
+       // Unlink dead klasses from subklass/sibling/implementor lists.
+       Klass::clean_weak_klass_links(unloading_occurred);
+     }
+ 
+     // Make sure the old links are no longer observable before purging
+     mutator_rendezvous();
+ 
+     {
+       // 2. This is the purging phase; delete the stale metadata that was unlinked
+ 
+       // Purge the metaspace
+       ClassLoaderDataGraph::purge();
+       // MetaspaceUtils::verify_metrics();
+       // Resize metaspace
+       MetaspaceGC::compute_new_size();
+     }
+   }
+ 
    // Unblock resurrection of weak/phantom references
    ZResurrection::unblock();
  
    // Enqueue Soft/Weak/Final/PhantomReferences. Note that this
    // must be done after unblocking resurrection. Otherwise the
***************
*** 556,566 ****
    ZWeakRootsIterator _weak_roots;
  
  public:
    ZVerifyRootsTask() :
        ZTask("ZVerifyRootsTask"),
!       _strong_roots(),
        _weak_roots() {}
  
    virtual void work() {
      ZVerifyRootOopClosure cl;
      _strong_roots.oops_do(&cl);
--- 597,607 ----
    ZWeakRootsIterator _weak_roots;
  
  public:
    ZVerifyRootsTask() :
        ZTask("ZVerifyRootsTask"),
!       _strong_roots(false),
        _weak_roots() {}
  
    virtual void work() {
      ZVerifyRootOopClosure cl;
      _strong_roots.oops_do(&cl);