diff -r be3f9bf8c3a6 -r 1de2255c6c2e hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp
--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Thu Apr 15 18:45:30 2010 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp	Fri Apr 16 08:48:16 2010 -0700
@@ -209,6 +209,15 @@
   HeapRegion::setup_heap_region_size(Arguments::min_heap_size());
   HeapRegionRemSet::setup_remset_size();
 
+  // Verify PLAB sizes
+  const uint region_size = HeapRegion::GrainWords;
+  if (YoungPLABSize > region_size || OldPLABSize > region_size) {
+    char buffer[128];
+    jio_snprintf(buffer, sizeof(buffer), "%sPLABSize should be at most %u",
+                 OldPLABSize > region_size ? "Old" : "Young", region_size);
+    vm_exit_during_initialization(buffer);
+  }
+
   _recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime());
   _prev_collection_pause_end_ms = os::elapsedTime() * 1000.0;