*** old/src/share/vm/runtime/sweeper.cpp	Fri Nov  8 14:10:12 2013
--- new/src/share/vm/runtime/sweeper.cpp	Fri Nov  8 14:10:12 2013

*** 110,153 ****
--- 110,155 ----
  
  void NMethodSweeper::record_sweep(nmethod* nm, int line) {
    if (_records != NULL) {
      _records[_sweep_index].traversal = _traversals;
      _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;
!     _records[_sweep_index].invocation = _invocations;
!     _records[_sweep_index].invocation = _sweep_fractions_left;
      _records[_sweep_index].compile_id = nm->compile_id();
      _records[_sweep_index].kind = nm->compile_kind();
      _records[_sweep_index].state = nm->_state;
      _records[_sweep_index].vep = nm->verified_entry_point();
      _records[_sweep_index].uep = nm->entry_point();
      _records[_sweep_index].line = line;
  
      _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
    }
  }
  #else
  #define SWEEP(nm)
  #endif
  
  nmethod* NMethodSweeper::_current                      = NULL; // Current nmethod
! long      NMethodSweeper::_traversals      = 0;    // Nof. stack traversals performed
  int       NMethodSweeper::_seen            = 0;    // Nof. nmethods we have currently processed in current pass of CodeCache
! long     NMethodSweeper::_traversals                   = 0;    // Stack scan count, also sweep ID.
+ long     NMethodSweeper::_time_counter                 = 0;    // Virtual time used to periodically invoke sweeper
+ long     NMethodSweeper::_last_sweep                   = 0;    // Value of _time_counter when the last sweep happened
+ int      NMethodSweeper::_seen                         = 0;    // Nof. nmethod we have currently processed in current pass of CodeCache
  int      NMethodSweeper::_flushed_count                = 0;    // Nof. nmethods flushed in current sweep
  int      NMethodSweeper::_zombified_count              = 0;    // Nof. nmethods made zombie in current sweep
! int       NMethodSweeper::_marked_count    = 0;    // Nof. nmethods marked for reclaim in current sweep
  
  volatile int NMethodSweeper::_invocations   = 0; // Nof. invocations left until we are completed with this pass
  volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.
! int      NMethodSweeper::_marked_for_reclamation_count = 0;    // Nof. nmethods marked for reclaim in current sweep
  
  jint      NMethodSweeper::_locked_seen               = 0;
  jint      NMethodSweeper::_not_entrant_seen_on_stack = 0;
  bool      NMethodSweeper::_request_mark_phase        = false;
  
  int       NMethodSweeper::_total_nof_methods_reclaimed = 0;
  jlong     NMethodSweeper::_total_time_sweeping         = 0;
  jlong     NMethodSweeper::_total_time_this_sweep       = 0;
  jlong     NMethodSweeper::_peak_sweep_time             = 0;
  jlong     NMethodSweeper::_peak_sweep_fraction_time    = 0;
+ volatile bool NMethodSweeper::_should_sweep            = true; // Indicates if we should invoke the sweeper
+ volatile int  NMethodSweeper::_sweep_fractions_left    = 0;    // Nof. invocations left until we are completed with this pass
+ volatile int  NMethodSweeper::_sweep_started           = 0;    // Flag to control conc sweeper
+ volatile int  NMethodSweeper::_bytes_changed           = 0;    // Counts the total nmethod size if the nmethod changed from:
+                                                                //   1) alive       -> not_entrant
+                                                                //   2) not_entrant -> zombie
+                                                                //   3) zombie      -> marked_for_reclamation
+ 
+ int   NMethodSweeper::_total_nof_methods_reclaimed     = 0;    // Accumulated nof methods flushed
+ jlong NMethodSweeper::_total_time_sweeping             = 0;    // Accumulated time sweeping
+ jlong NMethodSweeper::_total_time_this_sweep           = 0;    // Total time this sweep
+ jlong NMethodSweeper::_peak_sweep_time                 = 0;    // Peak time for a full sweep
+ jlong NMethodSweeper::_peak_sweep_fraction_time        = 0;    // Peak time sweeping one fraction
  int   NMethodSweeper::_hotness_counter_reset_val       = 0;
  
  
  class MarkActivationClosure: public CodeBlobClosure {
  public:

*** 195,237 ****
--- 197,272 ----
    // to scan stacks
    if (!MethodFlushing) {
      return;
    }
  
+   // Increase time so that we can estimate when to invoke the sweeper again.
+   _time_counter++;
+ 
    // Check for restart
    assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
-   if (!sweep_in_progress() && need_marking_phase()) {
      _seen = 0;
!     _invocations = NmethodSweepFraction;
!     _sweep_fractions_left = NmethodSweepFraction;
      _current = CodeCache::first_nmethod();
      _traversals += 1;
      _total_time_this_sweep = 0;
  
      if (PrintMethodFlushing) {
        tty->print_cr("### Sweep: stack traversal %d", _traversals);
      }
      Threads::nmethods_do(&mark_activation_closure);
  
      // reset the flags since we started a scan from the beginning.
      reset_nmethod_marking();
      _locked_seen = 0;
      _not_entrant_seen_on_stack = 0;
    } else {
      // Only set hotness counter
      Threads::nmethods_do(&set_hotness_closure);
    }
  
    OrderAccess::storestore();
  }
  
+ /**
+  * This function invokes the sweeper if at least one of the three conditions is met:
+  *    (1) The code cache is getting full
+  *    (2) There are sufficient state changes in/since the last sweep.
+  *    (3) We have not been sweeping for 'some time'
+  */
  void NMethodSweeper::possibly_sweep() {
    assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
    if (!MethodFlushing || !sweep_in_progress()) {
      return;
    }
  
    if (_invocations > 0) {
+   // If there was no state change while nmethod sweeping, 'should_sweep' will be false.
+   // This is one of the two places where should_sweep can be set to true. The general
+   // idea is as follows: If there is enough free space in the code cache, there is no
+   // need to invoke the sweeper. The following formula (which determines whether to invoke
+   // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes
+   // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore,
+   // the formula considers how much space in the code cache is currently used. Here are
+   // some examples that will (hopefully) help in understanding.
+   //
+   // Small ReservedCodeCacheSizes:  (e.g., < 16M) We invoke the sweeper every time, since
+   //                                              the result of the division is 0. This
+   //                                              keeps the used code cache size small
+   //                                              (important for embedded Java)
+   // Large ReservedCodeCacheSize :  (e.g., 256M + code cache is 10% full). The formula
+   //                                              computes: (256 / 16) - 1 = 15
+   //                                              As a result, we invoke the sweeper after
+   //                                              15 invocations of 'mark_active_nmethods.
+   // Large ReservedCodeCacheSize:   (e.g., 256M + code Cache is 90% full). The formula
+   //                                              computes: (256 / 16) - 10 = 6.
+   if (!_should_sweep) {
+     int time_since_last_sweep = _time_counter - _last_sweep;
+     int wait_until_next_sweep = (ReservedCodeCacheSize / (16 * M)) - time_since_last_sweep -
+                                 CodeCache::reverse_free_ratio();
+ 
+     if ((wait_until_next_sweep <= 0) || !CompileBroker::should_compile_new_jobs()) {
+       _should_sweep = true;
+     }
+   }
+ 
+   if (_should_sweep && _sweep_fractions_left > 0) {
      // Only one thread at a time will sweep
      jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
      if (old != 0) {
        return;
      }

*** 240,282 ****
--- 275,332 ----
        // Create the ring buffer for the logging code
        _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
        memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
      }
  #endif
      if (_invocations > 0) {
+ 
+     if (_sweep_fractions_left > 0) {
        sweep_code_cache();
!       _invocations--;
!       _sweep_fractions_left--;
+     }
+ 
+     // We are done with sweeping the code cache once.
+     if (_sweep_fractions_left == 0) {
+       _last_sweep = _time_counter;
+       // Reset flag; temporarily disables sweeper
+       _should_sweep = false;
+       // If there was enough state change, 'possibly_enable_sweeper()'
+       // sets '_should_sweep' to true
+       possibly_enable_sweeper();
+       // Reset _bytes_changed only if there was enough state change. _bytes_changed
+       // can further increase by calls to 'report_state_change'.
+       if (_should_sweep) {
+         _bytes_changed = 0;
+       }
      }
      _sweep_started = 0;
    }
  }
  
  void NMethodSweeper::sweep_code_cache() {
  
    jlong sweep_start_counter = os::elapsed_counter();
  
    _flushed_count                = 0;
    _zombified_count              = 0;
!   _marked_count    = 0;
!   _marked_for_reclamation_count = 0;
  
    if (PrintMethodFlushing && Verbose) {
!     tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations);
!     tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left);
    }
  
    if (!CompileBroker::should_compile_new_jobs()) {
      // If we have turned off compilations we might as well do full sweeps
      // in order to reach the clean state faster. Otherwise the sleeping compiler
      // threads will slow down sweeping.
!     _invocations = 1;
!     _sweep_fractions_left = 1;
    }
  
    // We want to visit all nmethods after NmethodSweepFraction
    // invocations so divide the remaining number of nmethods by the
    // remaining number of invocations.  This is only an estimate since
    // the number of nmethods changes during the sweep so the final
    // stage must iterate until it there are no more nmethods.
!   int todo = (CodeCache::nof_nmethods() - _seen) / _invocations;
!   int todo = (CodeCache::nof_nmethods() - _seen) / _sweep_fractions_left;
    int swept_count = 0;
  
  
    assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
    assert(!CodeCache_lock->owned_by_self(), "just checking");

*** 284,298 ****
--- 334,348 ----
    int freed_memory = 0;
    {
      MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
  
      // The last invocation iterates until there are no more nmethods
!     for (int i = 0; (i < todo || _invocations == 1) && _current != NULL; i++) {
!     for (int i = 0; (i < todo || _sweep_fractions_left == 1) && _current != NULL; i++) {
        swept_count++;
        if (SafepointSynchronize::is_synchronizing()) { // Safepoint request
          if (PrintMethodFlushing && Verbose) {
!           tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _invocations);
!           tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left);
          }
          MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
  
          assert(Thread::current()->is_Java_thread(), "should be java thread");
          JavaThread* thread = (JavaThread*)Thread::current();

*** 312,334 ****
--- 362,372 ----
        _seen++;
        _current = next;
      }
    }
  
!   assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");
  
    if (!sweep_in_progress() && !need_marking_phase() && (_locked_seen || _not_entrant_seen_on_stack)) {
      // we've completed a scan without making progress but there were
      // nmethods we were unable to process either because they were
      // locked or were still on stack. We don't have to aggressively
      // clean them up so just stop scanning. We could scan once more
      // but that complicates the control logic and it's unlikely to
      // matter much.
      if (PrintMethodFlushing) {
        tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
      }
    }
!   assert(_sweep_fractions_left > 1 || _current == NULL, "must have scanned the whole cache");
  
    jlong sweep_end_counter = os::elapsed_counter();
    jlong sweep_time = sweep_end_counter - sweep_start_counter;
    _total_time_sweeping  += sweep_time;
    _total_time_this_sweep += sweep_time;

*** 338,362 ****
--- 376,400 ----
    EventSweepCodeCache event(UNTIMED);
    if (event.should_commit()) {
      event.set_starttime(sweep_start_counter);
      event.set_endtime(sweep_end_counter);
      event.set_sweepIndex(_traversals);
!     event.set_sweepFractionIndex(NmethodSweepFraction - _invocations + 1);
!     event.set_sweepFractionIndex(NmethodSweepFraction - _sweep_fractions_left + 1);
      event.set_sweptCount(swept_count);
      event.set_flushedCount(_flushed_count);
!     event.set_markedCount(_marked_count);
!     event.set_markedCount(_marked_for_reclamation_count);
      event.set_zombifiedCount(_zombified_count);
      event.commit();
    }
  
  #ifdef ASSERT
    if(PrintMethodFlushing) {
!     tty->print_cr("### sweeper:      sweep time(%d): " INT64_FORMAT, _invocations, (jlong)sweep_time);
!     tty->print_cr("### sweeper:      sweep time(%d): " INT64_FORMAT, _sweep_fractions_left, (jlong)sweep_time);
    }
  #endif
  
!   if (_invocations == 1) {
!   if (_sweep_fractions_left == 1) {
      _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
      log_sweep("finished");
    }
  
    // Sweeper is the only case where memory is released, check here if it

*** 366,378 ****
--- 404,444 ----
    // cases when compilation was disabled although there is 4MB (or more) free
    // memory in the code cache. The reason is code cache fragmentation. Therefore,
    // it only makes sense to re-enable compilation if we have actually freed memory.
    // Note that typically several kB are released for sweeping 16MB of the code
    // cache. As a result, 'freed_memory' > 0 to restart the compiler.
!   if (UseCodeCacheFlushing && (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0))) {
      CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
      log_sweep("restart_compiler");
+     if (CompileBroker::should_print_compiler_warning()) {
+       warning("Freed %d bytes from code cache. Compiler has been enabled.", freed_memory);
+     }
+   }
+ }
+ 
+ /**
+  * This function updates the sweeper statistics that keep track of nmethods
+  * state changes. If there is 'enough' state change, the sweeper is invoked
+  * as soon as possible. There can be data races on _bytes_changed. The data
+  * races are benign, since it does not matter if we loose a couple of bytes.
+  * In the worst case we call the sweeper a little later. Also, we are guaranteed
+  * to invoke the sweeper if the code cache gets full.
+  */
+ void NMethodSweeper::report_state_change(nmethod* nm) {
+   _bytes_changed += nm->total_size();
+   possibly_enable_sweeper();
+ }
+ 
+ /**
+  * Function determines if there was 'enough' state change in the code cache to invoke
+  * the sweeper again. Currently, we determine 'enough' as more than 1% state change in
+  * the code cache since the last sweep.
+  */
+ void NMethodSweeper::possibly_enable_sweeper() {
+   double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100;
+   if (percent_changed > 1.0) {
+     _should_sweep = true;
    }
  }
  
  class NMethodMarker: public StackObj {
   private:

*** 422,434 ****
--- 488,497 ----
      if (nm->is_alive()) {
        // Clean inline caches that point to zombie/non-entrant methods
        MutexLocker cl(CompiledIC_lock);
        nm->cleanup_inline_caches();
        SWEEP(nm);
      } else {
        _locked_seen++;
        SWEEP(nm);
      }
      return freed_memory;
    }
  
    if (nm->is_zombie()) {

*** 446,478 ****
--- 509,538 ----
      } else {
        if (PrintMethodFlushing && Verbose) {
          tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
        }
        nm->mark_for_reclamation();
        request_nmethod_marking();
!       _marked_count++;
+       // Keep track of code cache state change
!       _bytes_changed += nm->total_size();
+       _marked_for_reclamation_count++;
        SWEEP(nm);
      }
    } else if (nm->is_not_entrant()) {
      // If there are no current activations of this method on the
      // stack we can safely convert it to a zombie method
      if (nm->can_not_entrant_be_converted()) {
        if (PrintMethodFlushing && Verbose) {
          tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
        }
+       // Code cache state change is tracked in make_zombie()
        nm->make_zombie();
        request_nmethod_marking();
        _zombified_count++;
        SWEEP(nm);
      } else {
        // Still alive, clean up its inline caches
        MutexLocker cl(CompiledIC_lock);
        nm->cleanup_inline_caches();
        // we coudn't transition this nmethod so don't immediately
        // request a rescan.  If this method stays on the stack for a
        // long time we don't want to keep rescanning the code cache.
        _not_entrant_seen_on_stack++;
        SWEEP(nm);
      }
    } else if (nm->is_unloaded()) {
      // Unloaded code, just make it a zombie
      if (PrintMethodFlushing && Verbose) {

*** 483,494 ****
--- 543,554 ----
        // No inline caches will ever point to osr methods, so we can just remove it
        freed_memory = nm->total_size();
        release_nmethod(nm);
        _flushed_count++;
      } else {
+       // Code cache state change is tracked in make_zombie()
        nm->make_zombie();
        request_nmethod_marking();
        _zombified_count++;
        SWEEP(nm);
      }
    } else {
      if (UseCodeCacheFlushing) {

*** 512,522 ****
--- 572,586 ----
            //    The second condition is necessary if we are dealing with very small code cache
            //    sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
            //    The second condition ensures that methods are not immediately made not-entrant
            //    after compilation.
            nm->make_not_entrant();
            request_nmethod_marking();
+           // Code cache state change is tracked in make_not_entrant()
+           if (PrintMethodFlushing && Verbose) {
+             tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f",
+                           nm->compile_id(), nm, nm->hotness_counter(), reset_val, threshold);
+           }
          }
        }
      }
      // Clean-up all inline caches that point to zombie/non-reentrant methods
      MutexLocker cl(CompiledIC_lock);