src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp

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rev 2869 : 7117303: VM uses non-monotonic time source and complains that it is non-monotonic
Summary: Replaces calls to os::javaTimeMillis(), which does not guarantee montonicity, in GC code to os::javaTimeNanos() with a suitable conversion factor. os::javaTimeNanos() mostly guarantees montonicity depending on the underlying OS implementation and, as a result, a better alternative. Changes in OS files are to make use of the newly defined constants in globalDefinitions.hpp.
Reviewed-by:

@@ -3396,21 +3396,24 @@
            "live objects skipped because closure is full");
   }
 }
 
 jlong PSParallelCompact::millis_since_last_gc() {
-  jlong ret_val = os::javaTimeMillis() - _time_of_last_gc;
+  // os::javaTimeMillis() does not guarantee monotonicity.
+  jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
+  jlong ret_val = now - _time_of_last_gc;
   // XXX See note in genCollectedHeap::millis_since_last_gc().
   if (ret_val < 0) {
-    NOT_PRODUCT(warning("time warp: %d", ret_val);)
+    NOT_PRODUCT(warning("time warp: "INT64_FORMAT, ret_val);)
     return 0;
   }
   return ret_val;
 }
 
 void PSParallelCompact::reset_millis_since_last_gc() {
-  _time_of_last_gc = os::javaTimeMillis();
+  // os::javaTimeMillis() does not guarantee monotonicity.
+  _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 }
 
 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
 {
   if (source() != destination()) {