8257901: ZGC: Take virtual memory usage into account when sizing heap

Reviewed-by: stefank, eosterlund, ayang, tschatzl

src/hotspot/share/gc/shared/gcArguments.cpp

@@ -172,3 +172,7 @@ void GCArguments::initialize_heap_flags_and_sizes() {
 
   DEBUG_ONLY(assert_flags();)
 }
+
+size_t GCArguments::heap_virtual_to_physical_ratio() {
+  return 1;
+}

src/hotspot/share/gc/shared/gcArguments.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -46,6 +46,11 @@ protected:
 public:
   virtual void initialize();
   virtual size_t conservative_max_heap_alignment() = 0;
+
+  // Used by heap size heuristics to determine max
+  // amount of address space to use for the heap.
+  virtual size_t heap_virtual_to_physical_ratio();
+
   virtual CollectedHeap* create_heap() = 0;
 
   // Allows GCs to tell external code if it's supported or not in the current setup.

src/hotspot/share/gc/z/zAddressSpaceLimit.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -24,6 +24,7 @@
 #include "precompiled.hpp"
 #include "gc/z/zAddressSpaceLimit.hpp"
 #include "gc/z/zGlobals.hpp"
+#include "runtime/globals.hpp"
 #include "runtime/os.hpp"
 #include "utilities/align.hpp"
 
@@ -46,6 +47,6 @@ size_t ZAddressSpaceLimit::mark_stack() {
 
 size_t ZAddressSpaceLimit::heap_view() {
   // Allow all heap views to occupy 50% of the address space
-  const size_t limit = address_space_limit() / 2 / ZHeapViews;
+  const size_t limit = address_space_limit() / MaxVirtMemFraction / ZHeapViews;
   return align_up(limit, ZGranuleSize);
 }

src/hotspot/share/gc/z/zArguments.cpp

@@ -25,6 +25,7 @@
 #include "gc/z/zAddressSpaceLimit.hpp"
 #include "gc/z/zArguments.hpp"
 #include "gc/z/zCollectedHeap.hpp"
+#include "gc/z/zGlobals.hpp"
 #include "gc/z/zHeuristics.hpp"
 #include "gc/shared/gcArguments.hpp"
 #include "runtime/globals.hpp"
@@ -94,6 +95,10 @@ void ZArguments::initialize() {
   }
 }
 
+size_t ZArguments::heap_virtual_to_physical_ratio() {
+  return ZHeapViews * ZVirtualToPhysicalRatio;
+}
+
 size_t ZArguments::conservative_max_heap_alignment() {
   return 0;
 }

src/hotspot/share/gc/z/zArguments.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -34,6 +34,7 @@ private:
 
   virtual void initialize();
   virtual size_t conservative_max_heap_alignment();
+  virtual size_t heap_virtual_to_physical_ratio();
   virtual CollectedHeap* create_heap();
 
   virtual bool is_supported() const;

src/hotspot/share/runtime/arguments.cpp

@@ -1655,11 +1655,18 @@ jint Arguments::set_ergonomics_flags() {
   return JNI_OK;
 }
 
-julong Arguments::limit_by_allocatable_memory(julong limit) {
+julong Arguments::limit_heap_by_allocatable_memory(julong limit) {
   julong max_allocatable;
   julong result = limit;
   if (os::has_allocatable_memory_limit(&max_allocatable)) {
-    result = MIN2(result, max_allocatable / MaxVirtMemFraction);
+    // The AggressiveHeap check is a temporary workaround to avoid calling
+    // GCarguments::heap_virtual_to_physical_ratio() before a GC has been
+    // selected. This works because AggressiveHeap implies UseParallelGC
+    // where we know the ratio will be 1. Once the AggressiveHeap option is
+    // removed, this can be cleaned up.
+    julong heap_virtual_to_physical_ratio = (AggressiveHeap ? 1 : GCConfig::arguments()->heap_virtual_to_physical_ratio());
+    julong fraction = MaxVirtMemFraction * heap_virtual_to_physical_ratio;
+    result = MIN2(result, max_allocatable / fraction);
   }
   return result;
 }
@@ -1775,12 +1782,12 @@ void Arguments::set_heap_size() {
     }
 #endif // _LP64
 
-    reasonable_max = limit_by_allocatable_memory(reasonable_max);
+    reasonable_max = limit_heap_by_allocatable_memory(reasonable_max);
 
     if (!FLAG_IS_DEFAULT(InitialHeapSize)) {
       // An initial heap size was specified on the command line,
       // so be sure that the maximum size is consistent.  Done
-      // after call to limit_by_allocatable_memory because that
+      // after call to limit_heap_by_allocatable_memory because that
       // method might reduce the allocation size.
       reasonable_max = MAX2(reasonable_max, (julong)InitialHeapSize);
     } else if (!FLAG_IS_DEFAULT(MinHeapSize)) {
@@ -1798,11 +1805,11 @@ void Arguments::set_heap_size() {
 
     reasonable_minimum = MIN2(reasonable_minimum, (julong)MaxHeapSize);
 
-    reasonable_minimum = limit_by_allocatable_memory(reasonable_minimum);
+    reasonable_minimum = limit_heap_by_allocatable_memory(reasonable_minimum);
 
     if (InitialHeapSize == 0) {
       julong reasonable_initial = (julong)((phys_mem * InitialRAMPercentage) / 100);
-      reasonable_initial = limit_by_allocatable_memory(reasonable_initial);
+      reasonable_initial = limit_heap_by_allocatable_memory(reasonable_initial);
 
       reasonable_initial = MAX3(reasonable_initial, reasonable_minimum, (julong)MinHeapSize);
       reasonable_initial = MIN2(reasonable_initial, (julong)MaxHeapSize);
@@ -1846,7 +1853,7 @@ jint Arguments::set_aggressive_heap_flags() {
   initHeapSize = MIN2(total_memory / (julong) 2,
           total_memory - (julong) 160 * M);
 
-  initHeapSize = limit_by_allocatable_memory(initHeapSize);
+  initHeapSize = limit_heap_by_allocatable_memory(initHeapSize);
 
   if (FLAG_IS_DEFAULT(MaxHeapSize)) {
     if (FLAG_SET_CMDLINE(MaxHeapSize, initHeapSize) != JVMFlag::SUCCESS) {

src/hotspot/share/runtime/arguments.hpp

@@ -363,9 +363,10 @@ class Arguments : AllStatic {
   static void set_use_compressed_klass_ptrs();
   static jint set_ergonomics_flags();
   static jint set_shared_spaces_flags_and_archive_paths();
-  // limits the given memory size by the maximum amount of memory this process is
-  // currently allowed to allocate or reserve.
-  static julong limit_by_allocatable_memory(julong size);
+  // Limits the given heap size by the maximum amount of virtual
+  // memory this process is currently allowed to use. It also takes
+  // the virtual-to-physical ratio of the current GC into account.
+  static julong limit_heap_by_allocatable_memory(julong size);
   // Setup heap size
   static void set_heap_size();