--- old/src/hotspot/share/gc/z/zBarrierSet.cpp	2020-05-29 12:04:25.000000000 +0200
+++ new/src/hotspot/share/gc/z/zBarrierSet.cpp	2020-05-29 12:04:25.000000000 +0200
@@ -95,3 +95,7 @@
   // Flush and free any remaining mark stacks
   ZHeap::heap()->mark_flush_and_free(thread);
 }
+
+void ZBarrierSet::print_on(outputStream* st) const {
+  st->print_cr("ZBarrierSet");
+}
--- old/src/hotspot/share/gc/z/zBarrierSet.hpp	2020-05-29 12:04:26.000000000 +0200
+++ new/src/hotspot/share/gc/z/zBarrierSet.hpp	2020-05-29 12:04:26.000000000 +0200
@@ -40,7 +40,7 @@
   virtual void on_thread_attach(Thread* thread);
   virtual void on_thread_detach(Thread* thread);
 
-  virtual void print_on(outputStream* st) const {}
+  virtual void print_on(outputStream* st) const;
 
   template <DecoratorSet decorators, typename BarrierSetT = ZBarrierSet>
   class AccessBarrier : public BarrierSet::AccessBarrier<decorators, BarrierSetT> {
--- old/src/hotspot/share/gc/z/zCollectedHeap.cpp	2020-05-29 12:04:26.000000000 +0200
+++ new/src/hotspot/share/gc/z/zCollectedHeap.cpp	2020-05-29 12:04:26.000000000 +0200
@@ -304,21 +304,34 @@
   _heap.print_on(st);
 }
 
+static const char* z_global_phase_string() {
+  switch (ZGlobalPhase) {
+  case ZPhaseMark: return "Mark";
+  case ZPhaseMarkCompleted: return "MarkCompleted";
+  case ZPhaseRelocate: return "Relocate";
+  default: assert(false, "Unknown ZGlobalPhase"); return "Unknown";
+  }
+}
+
 void ZCollectedHeap::print_on_error(outputStream* st) const {
+  st->print_cr( "ZGC Globals:");
+  st->print_cr( " GlobalPhase:       %u (%s)", ZGlobalPhase, z_global_phase_string());
+  st->print_cr( " GlobalSeqNum:      %u", ZGlobalSeqNum);
+  st->print_cr( " Offset Max:        " SIZE_FORMAT "%s (" PTR_FORMAT ")",
+              byte_size_in_exact_unit(ZAddressOffsetMax),
+              exact_unit_for_byte_size(ZAddressOffsetMax),
+              ZAddressOffsetMax);
+  st->print_cr( " Page Size Small:   " SIZE_FORMAT "M", ZPageSizeSmall / M);
+  st->print_cr( " Page Size Medium:  " SIZE_FORMAT "M", ZPageSizeMedium / M);
+  st->cr();
+  st->print_cr( "ZGC Metadata Bits:");
+  st->print_cr( " Good:              " PTR_FORMAT, ZAddressGoodMask);
+  st->print_cr( " Bad:               " PTR_FORMAT, ZAddressBadMask);
+  st->print_cr( " WeakBad:           " PTR_FORMAT, ZAddressWeakBadMask);
+  st->print_cr( " Marked:            " PTR_FORMAT, ZAddressMetadataMarked);
+  st->print_cr( " Remapped:          " PTR_FORMAT, ZAddressMetadataRemapped);
+  st->cr();
   CollectedHeap::print_on_error(st);
-
-  st->print_cr( "Heap");
-  st->print_cr( "     GlobalPhase:       %u", ZGlobalPhase);
-  st->print_cr( "     GlobalSeqNum:      %u", ZGlobalSeqNum);
-  st->print_cr( "     Offset Max:        " SIZE_FORMAT_W(-15) " (" PTR_FORMAT ")", ZAddressOffsetMax, ZAddressOffsetMax);
-  st->print_cr( "     Page Size Small:   " SIZE_FORMAT_W(-15) " (" PTR_FORMAT ")", ZPageSizeSmall, ZPageSizeSmall);
-  st->print_cr( "     Page Size Medium:  " SIZE_FORMAT_W(-15) " (" PTR_FORMAT ")", ZPageSizeMedium, ZPageSizeMedium);
-  st->print_cr( "Metadata Bits");
-  st->print_cr( "     Good:              " PTR_FORMAT, ZAddressGoodMask);
-  st->print_cr( "     Bad:               " PTR_FORMAT, ZAddressBadMask);
-  st->print_cr( "     WeakBad:           " PTR_FORMAT, ZAddressWeakBadMask);
-  st->print_cr( "     Marked:            " PTR_FORMAT, ZAddressMetadataMarked);
-  st->print_cr( "     Remapped:          " PTR_FORMAT, ZAddressMetadataRemapped);
 }
 
 void ZCollectedHeap::print_extended_on(outputStream* st) const {
--- old/src/hotspot/share/gc/z/zHeap.cpp	2020-05-29 12:04:27.000000000 +0200
+++ new/src/hotspot/share/gc/z/zHeap.cpp	2020-05-29 12:04:27.000000000 +0200
@@ -505,6 +505,7 @@
   _page_allocator.enable_deferred_delete();
 
   // Print all pages
+  st->print_cr("ZGC Page Table:");
   ZPageTableIterator iter(&_page_table);
   for (ZPage* page; iter.next(&page);) {
     page->print_on(st);
@@ -512,8 +513,6 @@
 
   // Allow pages to be deleted
   _page_allocator.enable_deferred_delete();
-
-  st->cr();
 }
 
 bool ZHeap::print_location(outputStream* st, uintptr_t addr) const {