src/hotspot/share/gc/g1/g1YoungRemSetSamplingThread.cpp

rev 52572 : JDK-8212657: Implementation of JDK-8204089 Promptly Return Unused Committed Memory from G1
Summary: Issue optional, default enabled, concurrent cycles when the VM is idle to reclaim unused internal and Java heap memory.
Reviewed-by:
Contributed-by: Rodrigo Bruno <rbruno@gsd.inesc-id.pt>, Ruslan Synytsky <rs@jelastic.com>, Thomas Schatzl <thomas.schatzl@oracle.com>
rev 52573 : [mq]: 8212657-stefanj-review

*** 62,72 ****
  
    // Check if enough time has passed since the last GC.
    uintx time_since_last_gc;
    if ((G1PeriodicGCInterval == 0) ||
        ((time_since_last_gc = (uintx)Universe::heap()->millis_since_last_gc()) < G1PeriodicGCInterval)) {
!     log_debug(gc, periodic)("Last GC occurred " UINTX_FORMAT "ms earlier which is higher than threshold " UINTX_FORMAT "ms. Skipping.",
                              time_since_last_gc, G1PeriodicGCInterval);
      return false;
    }
  
    // Check if load is lower than max.
--- 62,72 ----
  
    // Check if enough time has passed since the last GC.
    uintx time_since_last_gc;
    if ((G1PeriodicGCInterval == 0) ||
        ((time_since_last_gc = (uintx)Universe::heap()->millis_since_last_gc()) < G1PeriodicGCInterval)) {
!     log_debug(gc, periodic)("Last GC occurred " UINTX_FORMAT "ms before which is below threshold " UINTX_FORMAT "ms. Skipping.",
                              time_since_last_gc, G1PeriodicGCInterval);
      return false;
    }
  
    // Check if load is lower than max.
*** 79,88 ****
--- 79,98 ----
    }
  
    return true;
  }
  
+ void G1YoungRemSetSamplingThread::check_for_periodic_gc(){
+   if ((os::elapsedTime() - _last_periodic_gc_attempt_s) > (G1PeriodicGCInterval / 1000.0)) {
+     log_debug(gc, periodic)("Checking for periodic GC.");
+     if (should_start_periodic_gc()) {
+       Universe::heap()->collect(GCCause::_g1_periodic_collection);
+     }
+     _last_periodic_gc_attempt_s = os::elapsedTime();
+   }
+ }
+ 
  void G1YoungRemSetSamplingThread::run_service() {
    double vtime_start = os::elapsedVTime();
  
    while (!should_terminate()) {
      sample_young_list_rs_lengths();
*** 91,107 ****
        _vtime_accum = (os::elapsedVTime() - vtime_start);
      } else {
        _vtime_accum = 0.0;
      }
  
!     if ((os::elapsedTime() - _last_periodic_gc_attempt_s) > (G1PeriodicGCInterval / 1000.0)) {
!       log_debug(gc, periodic)("Checking for periodic GC.");
!       if (should_start_periodic_gc()) {
!         Universe::heap()->collect(GCCause::_g1_periodic_collection);
!       }
!       _last_periodic_gc_attempt_s = os::elapsedTime();
!     }
  
      sleep_before_next_cycle();
    }
  }
  
--- 101,111 ----
        _vtime_accum = (os::elapsedVTime() - vtime_start);
      } else {
        _vtime_accum = 0.0;
      }
  
!     check_for_periodic_gc();
  
      sleep_before_next_cycle();
    }
  }