1 /*
  2  * Copyright (c) 2018, 2020, 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 && 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 || 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 }
--- EOF ---