1 /*
   2  * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This code is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 only, as
   8  * published by the Free Software Foundation.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  *
  24  */
  25 
  26 #include "precompiled.hpp"
  27 #include "gc/shared/cardTableRS.hpp"
  28 #include "gc/shared/gcArguments.hpp"
  29 #include "logging/log.hpp"
  30 #include "runtime/arguments.hpp"
  31 #include "runtime/globals.hpp"
  32 #include "runtime/globals_extension.hpp"
  33 #include "utilities/defaultStream.hpp"
  34 #include "utilities/macros.hpp"
  35 
  36 size_t HeapAlignment = 0;
  37 size_t SpaceAlignment = 0;
  38 
  39 void GCArguments::initialize() {
  40   if (FullGCALot && FLAG_IS_DEFAULT(MarkSweepAlwaysCompactCount)) {
  41     MarkSweepAlwaysCompactCount = 1;  // Move objects every gc.
  42   }
  43 
  44   if (!(UseParallelGC || UseParallelOldGC) && FLAG_IS_DEFAULT(ScavengeBeforeFullGC)) {
  45     FLAG_SET_DEFAULT(ScavengeBeforeFullGC, false);
  46   }
  47 
  48   if (GCTimeLimit == 100) {
  49     // Turn off gc-overhead-limit-exceeded checks
  50     FLAG_SET_DEFAULT(UseGCOverheadLimit, false);
  51   }
  52 
  53   if (MinHeapFreeRatio == 100) {
  54     // Keeping the heap 100% free is hard ;-) so limit it to 99%.
  55     FLAG_SET_ERGO(MinHeapFreeRatio, 99);
  56   }
  57 
  58   if (!ClassUnloading) {
  59     // If class unloading is disabled, also disable concurrent class unloading.
  60     FLAG_SET_CMDLINE(ClassUnloadingWithConcurrentMark, false);
  61   }
  62 
  63   if (!FLAG_IS_DEFAULT(AllocateOldGenAt)) {
  64     // CompressedOops not supported when AllocateOldGenAt is set.
  65     LP64_ONLY(FLAG_SET_DEFAULT(UseCompressedOops, false));
  66     LP64_ONLY(FLAG_SET_DEFAULT(UseCompressedClassPointers, false));
  67     // When AllocateOldGenAt is set, we cannot use largepages for entire heap memory.
  68     // Only young gen which is allocated in dram can use large pages, but we currently don't support that.
  69     FLAG_SET_DEFAULT(UseLargePages, false);
  70   }
  71 }
  72 
  73 void GCArguments::initialize_heap_sizes() {
  74   initialize_alignments();
  75   initialize_heap_flags_and_sizes();
  76   initialize_size_info();
  77 }
  78 
  79 size_t GCArguments::compute_heap_alignment() {
  80   // The card marking array and the offset arrays for old generations are
  81   // committed in os pages as well. Make sure they are entirely full (to
  82   // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
  83   // byte entry and the os page size is 4096, the maximum heap size should
  84   // be 512*4096 = 2MB aligned.
  85 
  86   size_t alignment = CardTableRS::ct_max_alignment_constraint();
  87 
  88   if (UseLargePages) {
  89       // In presence of large pages we have to make sure that our
  90       // alignment is large page aware.
  91       alignment = lcm(os::large_page_size(), alignment);
  92   }
  93 
  94   return alignment;
  95 }
  96 
  97 bool GCArguments::check_args_consistency() {
  98   bool status = true;
  99   if (!FLAG_IS_DEFAULT(AllocateHeapAt) && !FLAG_IS_DEFAULT(AllocateOldGenAt)) {
 100     jio_fprintf(defaultStream::error_stream(),
 101       "AllocateHeapAt and AllocateOldGenAt cannot be used together.\n");
 102     status = false;
 103   }
 104   if (!FLAG_IS_DEFAULT(AllocateOldGenAt) && (UseSerialGC || UseConcMarkSweepGC || UseEpsilonGC || UseZGC)) {
 105     jio_fprintf(defaultStream::error_stream(),
 106       "AllocateOldGenAt is not supported for selected GC.\n");
 107     status = false;
 108   }
 109   return status;
 110 }
 111 
 112 #ifdef ASSERT
 113 void GCArguments::assert_flags() {
 114   assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes");
 115   assert(InitialHeapSize % HeapAlignment == 0, "InitialHeapSize alignment");
 116   assert(MaxHeapSize % HeapAlignment == 0, "MaxHeapSize alignment");
 117 }
 118 
 119 void GCArguments::assert_size_info() {
 120   assert(MaxHeapSize >= MinHeapSize, "Ergonomics decided on incompatible minimum and maximum heap sizes");
 121   assert(InitialHeapSize >= MinHeapSize, "Ergonomics decided on incompatible initial and minimum heap sizes");
 122   assert(MaxHeapSize >= InitialHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes");
 123   assert(MinHeapSize % HeapAlignment == 0, "MinHeapSize alignment");
 124   assert(InitialHeapSize % HeapAlignment == 0, "InitialHeapSize alignment");
 125   assert(MaxHeapSize % HeapAlignment == 0, "MaxHeapSize alignment");
 126 }
 127 #endif // ASSERT
 128 
 129 void GCArguments::initialize_size_info() {
 130   log_debug(gc, heap)("Minimum heap " SIZE_FORMAT "  Initial heap " SIZE_FORMAT "  Maximum heap " SIZE_FORMAT,
 131                       MinHeapSize, InitialHeapSize, MaxHeapSize);
 132 
 133   DEBUG_ONLY(assert_size_info();)
 134 }
 135 
 136 void GCArguments::initialize_heap_flags_and_sizes() {
 137   assert(SpaceAlignment != 0, "Space alignment not set up properly");
 138   assert(HeapAlignment != 0, "Heap alignment not set up properly");
 139   assert(HeapAlignment >= SpaceAlignment,
 140          "HeapAlignment: " SIZE_FORMAT " less than SpaceAlignment: " SIZE_FORMAT,
 141          HeapAlignment, SpaceAlignment);
 142   assert(HeapAlignment % SpaceAlignment == 0,
 143          "HeapAlignment: " SIZE_FORMAT " not aligned by SpaceAlignment: " SIZE_FORMAT,
 144          HeapAlignment, SpaceAlignment);
 145 
 146   if (FLAG_IS_CMDLINE(MaxHeapSize)) {
 147     if (FLAG_IS_CMDLINE(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
 148       vm_exit_during_initialization("Initial heap size set to a larger value than the maximum heap size");
 149     }
 150     if (FLAG_IS_CMDLINE(MinHeapSize) && MaxHeapSize < MinHeapSize) {
 151       vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
 152     }
 153   }
 154 
 155   // Check heap parameter properties
 156   if (MaxHeapSize < 2 * M) {
 157     vm_exit_during_initialization("Too small maximum heap");
 158   }
 159   if (InitialHeapSize < M) {
 160     vm_exit_during_initialization("Too small initial heap");
 161   }
 162   if (MinHeapSize < M) {
 163     vm_exit_during_initialization("Too small minimum heap");
 164   }
 165 
 166   // User inputs from -Xmx and -Xms must be aligned
 167   // Write back to flags if the values changed
 168   if (!is_aligned(MinHeapSize, HeapAlignment)) {
 169     FLAG_SET_ERGO(MinHeapSize, align_up(MinHeapSize, HeapAlignment));
 170   }
 171   if (!is_aligned(InitialHeapSize, HeapAlignment)) {
 172     FLAG_SET_ERGO(InitialHeapSize, align_up(InitialHeapSize, HeapAlignment));
 173   }
 174   if (!is_aligned(MaxHeapSize, HeapAlignment)) {
 175     FLAG_SET_ERGO(MaxHeapSize, align_up(MaxHeapSize, HeapAlignment));
 176   }
 177 
 178   if (FLAG_IS_CMDLINE(InitialHeapSize) && FLAG_IS_CMDLINE(MinHeapSize) &&
 179       InitialHeapSize < MinHeapSize) {
 180     vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
 181   }
 182 
 183   if (!FLAG_IS_DEFAULT(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
 184     FLAG_SET_ERGO(MaxHeapSize, InitialHeapSize);
 185   } else if (!FLAG_IS_DEFAULT(MaxHeapSize) && InitialHeapSize > MaxHeapSize) {
 186     FLAG_SET_ERGO(InitialHeapSize, MaxHeapSize);
 187     if (InitialHeapSize < MinHeapSize) {
 188       FLAG_SET_ERGO(MinHeapSize, InitialHeapSize);
 189     }
 190   }
 191 
 192   if (FLAG_IS_DEFAULT(SoftMaxHeapSize)) {
 193     FLAG_SET_ERGO(SoftMaxHeapSize, MaxHeapSize);
 194   }
 195 
 196   FLAG_SET_ERGO(MinHeapDeltaBytes, align_up(MinHeapDeltaBytes, SpaceAlignment));
 197 
 198   DEBUG_ONLY(assert_flags();)
 199 }