src/share/vm/runtime/arguments.cpp

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rev 3708 : 8000244: G1: Ergonomically set MarkStackSize and use virtual space for global marking stack
Summary: Set the value of MarkStackSize to a value based on the number of parallel marking threads with a reasonable minimum. Expand the marking stack if we have to restart marking due to an overflow up to a reasonable maximum. Allocate the underlying space for the marking stack from virtual memory.
Reviewed-by: jmasa

@@ -1500,17 +1500,16 @@
   if (ParallelGCThreads == 0) {
     FLAG_SET_DEFAULT(ParallelGCThreads,
                      Abstract_VM_Version::parallel_worker_threads());
   }
 
-  if (FLAG_IS_DEFAULT(MarkStackSize)) {
-    FLAG_SET_DEFAULT(MarkStackSize, 128 * TASKQUEUE_SIZE);
-  }
-  if (PrintGCDetails && Verbose) {
-    tty->print_cr("MarkStackSize: %uk  MarkStackSizeMax: %uk",
-      MarkStackSize / K, MarkStackSizeMax / K);
-    tty->print_cr("ConcGCThreads: %u", ConcGCThreads);
+  // MarkStackSize will be set (if it hasn't been set by the user)
+  // when concurrent marking is initialized.
+  // Its value will be based upon the number of parallel marking threads.
+  // But we do set the maximum mark stack size here.
+  if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
+    FLAG_SET_DEFAULT(MarkStackSizeMax, 128 * TASKQUEUE_SIZE);
   }
 
   if (FLAG_IS_DEFAULT(GCTimeRatio) || GCTimeRatio == 0) {
     // In G1, we want the default GC overhead goal to be higher than
     // say in PS. So we set it here to 10%. Otherwise the heap might

@@ -1518,10 +1517,16 @@
     // fact, even 10% seems to not be high enough in some cases
     // (especially small GC stress tests that the main thing they do
     // is allocation). We might consider increase it further.
     FLAG_SET_DEFAULT(GCTimeRatio, 9);
   }
+
+  if (PrintGCDetails && Verbose) {
+    tty->print_cr("MarkStackSize: %uk  MarkStackSizeMax: %uk",
+      MarkStackSize / K, MarkStackSizeMax / K);
+    tty->print_cr("ConcGCThreads: %u", ConcGCThreads);
+  }
 }
 
 void Arguments::set_heap_size() {
   if (!FLAG_IS_DEFAULT(DefaultMaxRAMFraction)) {
     // Deprecated flag

@@ -1976,10 +1981,13 @@
   status = status && verify_object_alignment();
 
   status = status && verify_min_value(ClassMetaspaceSize, 1*M,
                                       "ClassMetaspaceSize");
 
+  status = status && verify_interval(MarkStackSizeMax,
+                                  1, (max_jint - 1), "MarkStackSizeMax");
+
 #ifdef SPARC
   if (UseConcMarkSweepGC || UseG1GC) {
     // Issue a stern warning if the user has explicitly set
     // UseMemSetInBOT (it is known to cause issues), but allow
     // use for experimentation and debugging.