1 /*
2 * Copyright (c) 2011, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
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20 * or visit www.oracle.com if you need additional information or have any
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23 */
24
25 #ifndef SHARE_VM_GC_G1_G1MONITORINGSUPPORT_HPP
26 #define SHARE_VM_GC_G1_G1MONITORINGSUPPORT_HPP
27
28 #include "gc/shared/collectorCounters.hpp"
29 #include "gc/shared/generationCounters.hpp"
30 #include "services/memoryManager.hpp"
31 #include "services/memoryService.hpp"
32 #include "runtime/mutex.hpp"
33
34 class CollectorCounters;
35 class G1CollectedHeap;
36 class HSpaceCounters;
37 class MemoryPool;
38
39 // Class for monitoring logical spaces in G1. It provides data for
40 // both G1's jstat counters as well as G1's memory pools.
41 //
42 // G1 splits the heap into heap regions and each heap region belongs
43 // to one of the following categories:
44 //
45 // * eden : regions that have been allocated since the last GC
46 // * survivors : regions with objects that survived the last few GCs
47 // * old : long-lived non-humongous regions
48 // * humongous : humongous regions
49 // * archive : archive regions
50 // * free : free regions
51 //
52 // The combination of eden and survivor regions form the equivalent of
53 // the young generation in the other GCs. The combination of old,
54 // humongous, and archive regions form the equivalent of the old
55 // generation in the other GCs. Archive regions are permanently
56 // allocated during heap initialization, e.g., for CDS. Free regions
57 // do not have a good equivalent in the other GCs, given that they can
58 // be allocated as any of the other region types.
59 //
60 // The monitoring tools expect the heap to contain one or more
61 // generations (young, old) and each generation to contain one or
62 // more spaces (young has eden and survivor, old has old, humongous and
63 // archive). Given that G1 does not maintain those spaces physically
64 // (e.g., the set of non-contiguous eden regions can be considered as
65 // a "logical" space), we provide the illusion that those generations and
66 // spaces exist. In reality, each generation and space refers to a set
67 // of heap regions that are potentially non-contiguous.
68 //
69 // This class provides interfaces to access the min, current, and max
70 // capacity and current occupancy for each of G1's logical spaces and
71 // generations we expose to the monitoring tools. Also provided are
72 // counters for G1 concurrent collections and stop-the-world full heap
73 // collections.
74 //
75 // Below is a description of how the various sizes are calculated.
76 //
77 // * Current Capacity
78 //
79 // - heap_capacity = current heap capacity (e.g., current committed size)
80 // - young_gen_capacity = current max young gen target capacity
81 // (i.e., young gen target capacity + max allowed expansion capacity)
82 // - survivor_capacity = current survivor region capacity
83 // - eden_capacity = young_gen_capacity - survivor_capacity
84 // In legacy mode:
85 // - old_capacity = heap_capacity - young_gen_capacity
86 // Otherwise:
87 // - humongous_capacity = sum of humongous regions allocated
88 // - archive_capacity = sum of archive regions allocated
89 // - old_capacity = heap_capacity - young_gen_capacity -
90 // humongous_capacity - archive_capacity
91 //
92 // What we do in the above is to distribute the free regions among
93 // eden_capacity and old_capacity.
94 //
95 // * Occupancy
96 //
97 // - young_gen_committed = current young region capacity
98 // - survivor_used = survivor_capacity
99 // - eden_used = young_gen_used - survivor_used
100 // In legacy mode:
101 // - old_used = overall_used - young_gen_used
102 // Otherwise:
103 // - humongous_used = sum of humongous regions allocated
104 // - archive_used = sum of archive regions allocated
105 // - old_used = overall_used - young_gen_used -
106 // humongous_used - archive_used
107 //
108 // * Min Capacity
109 //
110 // We set this to 0 for all spaces.
111 //
112 // * Max Capacity
113 //
114 // For jstat, we set the max capacity of all spaces to heap_capacity,
115 // given that we don't always have a reasonable upper bound on how big
116 // each space can grow. For the memory pools, we make the max
117 // capacity undefined with the exception of the old memory pool for
118 // which we make the max capacity same as the max heap capacity. This
119 // allows users to sum memory pool max capacities to get something
120 // reasonable.
121 //
122 // We update all the above synchronously and we store the results in
123 // this singleton class so we can just read them out when needed. A subtle
124 // point is that all the above sizes must be recalculated when the old
125 // gen changes capacity (after a GC or after a humongous allocation)
126 // but only the eden occupancy changes when a new eden region is
127 // allocated. So, in the latter case we have minimal recalculation to
128 // do, but we don't both special-casing it because doing the full
129 // recalculation is quite fast.
130
131 class G1MonitoringSupport : public CHeapObj<mtGC> {
132 friend class VMStructs;
133 friend class G1MonitoringScope;
134
135 G1CollectedHeap* _g1h;
136
137 // java.lang.management MemoryManager and MemoryPool support
138
139 bool _use_legacy_monitoring; // For vmStructs and hsdb
140
141 GCMemoryManager _full_memory_manager;
142 // Legacy monitoring
143 GCMemoryManager _incremental_memory_manager;
144 // Default monitoring
145 GCMemoryManager _young_memory_manager;
146 GCMemoryManager _mixed_memory_manager;
147 GCMemoryManager _conc_memory_manager;
148
149 MemoryPool* _eden_space_pool;
150 MemoryPool* _survivor_space_pool;
151 MemoryPool* _old_space_pool;
152 MemoryPool* _archive_space_pool;
153 MemoryPool* _humongous_space_pool;
154
155 // jstat performance counters
156 // incremental collections both young and mixed
157 CollectorCounters* _incremental_collection_counters;
158 // full stop-the-world collections
159 CollectorCounters* _full_collection_counters;
160 // stop-the-world phases in G1
161 CollectorCounters* _conc_collection_counters;
162 // young collection set counters. The _eden_counters,
163 // _from_counters, and _to_counters are associated with
164 // this "generational" counter.
165 GenerationCounters* _young_gen_counters;
166 // old collection set counters. The _old_space_counters
167 // below are associated with this "generational" counter.
168 GenerationCounters* _old_gen_counters;
169 // Counters for the capacity and used for
170 // the whole heap
171 HSpaceCounters* _old_space_counters;
172 // the young collection
173 HSpaceCounters* _eden_space_counters;
174 // the survivor collection (only one, _to_counters, is actively used)
175 HSpaceCounters* _from_space_counters;
176 HSpaceCounters* _to_space_counters;
177
178 // When it's appropriate to recalculate the various sizes (at the
179 // end of a GC, when a new eden region is allocated, etc.) we store
180 // them here so that we can easily report them when needed and not
181 // have to recalculate them every time.
182
183 size_t _overall_committed;
184 size_t _overall_used;
185
186 size_t _young_gen_committed;
187
188 size_t _eden_space_committed;
189 size_t _eden_space_used;
190 size_t _survivor_space_committed;
191 size_t _survivor_space_used;
192
193 size_t _old_space_committed;
194 size_t _old_space_used;
195 size_t _archive_space_committed;
196 size_t _archive_space_used;
197
198 size_t _humongous_space_committed;
199 size_t _humongous_space_used;
200
201 // It returns x - y if x > y, 0 otherwise.
202 // As described in the comment above, some of the inputs to the
203 // calculations we have to do are obtained concurrently and hence
204 // may be inconsistent with each other. So, this provides a
205 // defensive way of performing the subtraction and avoids the value
206 // going negative (which would mean a very large result, given that
207 // the parameter are size_t).
208 static size_t subtract_up_to_zero(size_t x, size_t y) {
209 if (x > y) {
210 return x - y;
211 } else {
212 return 0;
213 }
214 }
215
216 // Recalculate all the space sizes.
217 void recalculate_sizes();
218
219 public:
220 G1MonitoringSupport(G1CollectedHeap* g1h);
221 ~G1MonitoringSupport();
222
223 void initialize_serviceability();
224
225 GrowableArray<GCMemoryManager*> memory_managers();
226 GrowableArray<MemoryPool*> memory_pools();
227
228 bool use_legacy_monitoring() { return _use_legacy_monitoring; }
229 GCMemoryManager* conc_memory_manager() { return &_conc_memory_manager; }
230
231 // Unfortunately, the jstat tool assumes that no space has 0
232 // capacity. In our case, given that each space is logical, it's
233 // possible that no regions will be allocated to it, hence to have 0
234 // capacity (e.g., if there are no survivor regions, the survivor
235 // space has 0 capacity). The way we deal with this is to always pad
236 // each capacity value we report to jstat by a very small amount to
237 // make sure that it's never zero. Given that we sometimes have to
238 // report a capacity of a generation that contains several spaces
239 // (e.g., young gen includes one eden, two survivor spaces), the
240 // mult parameter is provided in order to adding the appropriate
241 // padding multiple times so that the capacities add up correctly.
242 static size_t pad_capacity(size_t size_bytes, size_t mult = 1) {
243 return size_bytes + MinObjAlignmentInBytes * mult;
244 }
245
246 // Recalculate all the space sizes from scratch and update
247 // all jstat counters accordingly.
248 void update_sizes();
249 // Recalculate all the space sizes from scratch, but update
250 // just the eden size and jstat counters.
251 void update_eden_size();
252
253 CollectorCounters* conc_collection_counters() {
254 return _conc_collection_counters;
255 }
256
257 // Monitoring support used by
258 // MemoryService
259 // jstat counters
260 // Tracing
261 // Values may not be consistent wrt to each other.
262
263 size_t young_gen_committed() { return _young_gen_committed; }
264
265 size_t eden_space_used() { return _eden_space_used; }
266 size_t survivor_space_used() { return _survivor_space_used; }
267
268 size_t old_gen_committed();
269 size_t old_gen_used();
270
271 size_t old_space_committed() { return _old_space_committed; }
272 size_t old_space_used() { return _old_space_used; }
273 size_t archive_space_used() { return _archive_space_used; }
274
275 size_t humongous_space_used() { return _humongous_space_used; }
276
277 // Monitoring support for MemoryPools. Values in the returned MemoryUsage are
278 // guaranteed to be consistent with each other.
279 MemoryUsage memory_usage();
280 MemoryUsage eden_space_memory_usage(size_t initial_size, size_t max_size);
281 MemoryUsage survivor_space_memory_usage(size_t initial_size, size_t max_size);
282 MemoryUsage old_space_memory_usage(size_t initial_size, size_t max_size);
283 MemoryUsage archive_space_memory_usage(size_t initial_size, size_t max_size);
284 MemoryUsage humongous_space_memory_usage(size_t initial_size, size_t max_size);
285 };
286
287 // TraceMemoryManagerStats for concurrent cycle.
288 class TraceConcMemoryManagerStats : public TraceMemoryManagerStats {
289 public:
290 enum Stage {
291 CycleStart,
292 Remark,
293 Cleanup,
294 CycleEnd
295 };
296 TraceConcMemoryManagerStats(Stage stage, GCCause::Cause cause);
297 };
298
299 // Scope object for java.lang.management support.
300 class G1MonitoringScope : public StackObj {
301 TraceCollectorStats _tcs;
302 TraceMemoryManagerStats _tms; // full, mixed, or young (default)
303 TraceMemoryManagerStats _tms_incremental; // mixed and young (legacy)
304 public:
305 G1MonitoringScope(G1MonitoringSupport* g1mm, bool full_gc, bool mixed_gc);
306 };
307
308 #endif // SHARE_VM_GC_G1_G1MONITORINGSUPPORT_HPP