29 #include "memory/generation.hpp"
30
31 // A "SharedHeap" is an implementation of a java heap for HotSpot. This
32 // is an abstract class: there may be many different kinds of heaps. This
33 // class defines the functions that a heap must implement, and contains
34 // infrastructure common to all heaps.
35
36 class Generation;
37 class BarrierSet;
38 class GenRemSet;
39 class Space;
40 class SpaceClosure;
41 class OopClosure;
42 class OopsInGenClosure;
43 class ObjectClosure;
44 class SubTasksDone;
45 class WorkGang;
46 class FlexibleWorkGang;
47 class CollectorPolicy;
48 class KlassClosure;
49
50 // Note on use of FlexibleWorkGang's for GC.
51 // There are three places where task completion is determined.
52 // In
53 // 1) ParallelTaskTerminator::offer_termination() where _n_threads
54 // must be set to the correct value so that count of workers that
55 // have offered termination will exactly match the number
56 // working on the task. Tasks such as those derived from GCTask
57 // use ParallelTaskTerminator's. Tasks that want load balancing
58 // by work stealing use this method to gauge completion.
59 // 2) SubTasksDone has a variable _n_threads that is used in
60 // all_tasks_completed() to determine completion. all_tasks_complete()
61 // counts the number of tasks that have been done and then reset
62 // the SubTasksDone so that it can be used again. When the number of
63 // tasks is set to the number of GC workers, then _n_threads must
64 // be set to the number of active GC workers. G1CollectedHeap,
65 // HRInto_G1RemSet, GenCollectedHeap and SharedHeap have SubTasksDone.
66 // This seems too many.
67 // 3) SequentialSubTasksDone has an _n_threads that is used in
68 // a way similar to SubTasksDone and has the same dependency on the
86 // to a value > 1 before a task that you would like executed in parallel
87 // and then to set it to 0 after that task has completed. A value of
88 // 0 is a "special" value in set_n_threads() which translates to
89 // setting _n_threads to 1.
90 //
91 // Some code uses _n_termination to decide if work should be done in
92 // parallel. The notorious possibly_parallel_oops_do() in threads.cpp
93 // is an example of such code. Look for variable "is_par" for other
94 // examples.
95 //
96 // The active_workers is not reset to 0 after a parallel phase. It's
97 // value may be used in later phases and in one instance at least
98 // (the parallel remark) it has to be used (the parallel remark depends
99 // on the partitioning done in the previous parallel scavenge).
100
101 class SharedHeap : public CollectedHeap {
102 friend class VMStructs;
103
104 friend class VM_GC_Operation;
105 friend class VM_CGC_Operation;
106
107 private:
108 // For claiming strong_roots tasks.
109 SubTasksDone* _process_strong_tasks;
110
111 protected:
112 // There should be only a single instance of "SharedHeap" in a program.
113 // This is enforced with the protected constructor below, which will also
114 // set the static pointer "_sh" to that instance.
115 static SharedHeap* _sh;
116
117 // A gc policy, controls global gc resource issues
118 CollectorPolicy *_collector_policy;
119
120 // See the discussion below, in the specification of the reader function
121 // for this variable.
122 int _strong_roots_parity;
123
124 // If we're doing parallel GC, use this gang of threads.
125 FlexibleWorkGang* _workers;
126
223 public:
224 enum ScanningOption {
225 SO_None = 0x0,
226 SO_AllCodeCache = 0x8,
227 SO_ScavengeCodeCache = 0x10
228 };
229
230 FlexibleWorkGang* workers() const { return _workers; }
231
232 // Invoke the "do_oop" method the closure "roots" on all root locations.
233 // The "so" argument determines which roots the closure is applied to:
234 // "SO_None" does none;
235 // "SO_AllCodeCache" applies the closure to all elements of the CodeCache.
236 // "SO_ScavengeCodeCache" applies the closure to elements on the scavenge root list in the CodeCache.
237 void process_roots(bool activate_scope,
238 ScanningOption so,
239 OopClosure* strong_roots,
240 OopClosure* weak_roots,
241 CLDClosure* strong_cld_closure,
242 CLDClosure* weak_cld_closure,
243 CodeBlobClosure* code_roots);
244 void process_all_roots(bool activate_scope,
245 ScanningOption so,
246 OopClosure* roots,
247 CLDClosure* cld_closure,
248 CodeBlobClosure* code_roots);
249 void process_strong_roots(bool activate_scope,
250 ScanningOption so,
251 OopClosure* roots,
252 CLDClosure* cld_closure,
253 CodeBlobClosure* code_roots);
254
255
256 // Apply "root_closure" to the JNI weak roots..
257 void process_weak_roots(OopClosure* root_closure);
258
259 // The functions below are helper functions that a subclass of
260 // "SharedHeap" can use in the implementation of its virtual
261 // functions.
262
263 public:
264
265 // Do anything common to GC's.
266 virtual void gc_prologue(bool full) = 0;
267 virtual void gc_epilogue(bool full) = 0;
268
269 // Sets the number of parallel threads that will be doing tasks
270 // (such as process roots) subsequently.
271 virtual void set_par_threads(uint t);
272
273 int n_termination();
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29 #include "memory/generation.hpp"
30
31 // A "SharedHeap" is an implementation of a java heap for HotSpot. This
32 // is an abstract class: there may be many different kinds of heaps. This
33 // class defines the functions that a heap must implement, and contains
34 // infrastructure common to all heaps.
35
36 class Generation;
37 class BarrierSet;
38 class GenRemSet;
39 class Space;
40 class SpaceClosure;
41 class OopClosure;
42 class OopsInGenClosure;
43 class ObjectClosure;
44 class SubTasksDone;
45 class WorkGang;
46 class FlexibleWorkGang;
47 class CollectorPolicy;
48 class KlassClosure;
49 class GCPhaseTimeTracker;
50
51 // Note on use of FlexibleWorkGang's for GC.
52 // There are three places where task completion is determined.
53 // In
54 // 1) ParallelTaskTerminator::offer_termination() where _n_threads
55 // must be set to the correct value so that count of workers that
56 // have offered termination will exactly match the number
57 // working on the task. Tasks such as those derived from GCTask
58 // use ParallelTaskTerminator's. Tasks that want load balancing
59 // by work stealing use this method to gauge completion.
60 // 2) SubTasksDone has a variable _n_threads that is used in
61 // all_tasks_completed() to determine completion. all_tasks_complete()
62 // counts the number of tasks that have been done and then reset
63 // the SubTasksDone so that it can be used again. When the number of
64 // tasks is set to the number of GC workers, then _n_threads must
65 // be set to the number of active GC workers. G1CollectedHeap,
66 // HRInto_G1RemSet, GenCollectedHeap and SharedHeap have SubTasksDone.
67 // This seems too many.
68 // 3) SequentialSubTasksDone has an _n_threads that is used in
69 // a way similar to SubTasksDone and has the same dependency on the
87 // to a value > 1 before a task that you would like executed in parallel
88 // and then to set it to 0 after that task has completed. A value of
89 // 0 is a "special" value in set_n_threads() which translates to
90 // setting _n_threads to 1.
91 //
92 // Some code uses _n_termination to decide if work should be done in
93 // parallel. The notorious possibly_parallel_oops_do() in threads.cpp
94 // is an example of such code. Look for variable "is_par" for other
95 // examples.
96 //
97 // The active_workers is not reset to 0 after a parallel phase. It's
98 // value may be used in later phases and in one instance at least
99 // (the parallel remark) it has to be used (the parallel remark depends
100 // on the partitioning done in the previous parallel scavenge).
101
102 class SharedHeap : public CollectedHeap {
103 friend class VMStructs;
104
105 friend class VM_GC_Operation;
106 friend class VM_CGC_Operation;
107 public:
108 // The set of potentially parallel tasks in root scanning.
109 enum SH_process_roots_tasks {
110 SH_PS_Threads_oops_do,
111 SH_PS_StringTable_oops_do,
112 SH_PS_Universe_oops_do,
113 SH_PS_JNIHandles_oops_do,
114 SH_PS_ObjectSynchronizer_oops_do,
115 SH_PS_FlatProfiler_oops_do,
116 SH_PS_Management_oops_do,
117 SH_PS_SystemDictionary_oops_do,
118 SH_PS_ClassLoaderDataGraph_oops_do,
119 SH_PS_jvmti_oops_do,
120 SH_PS_CodeCache_oops_do,
121 // Leave this one last.
122 SH_PS_NumElements
123 };
124
125 static const char* ext_roots_task_str(uint task);
126 private:
127 // For claiming strong_roots tasks.
128 SubTasksDone* _process_strong_tasks;
129
130 protected:
131 // There should be only a single instance of "SharedHeap" in a program.
132 // This is enforced with the protected constructor below, which will also
133 // set the static pointer "_sh" to that instance.
134 static SharedHeap* _sh;
135
136 // A gc policy, controls global gc resource issues
137 CollectorPolicy *_collector_policy;
138
139 // See the discussion below, in the specification of the reader function
140 // for this variable.
141 int _strong_roots_parity;
142
143 // If we're doing parallel GC, use this gang of threads.
144 FlexibleWorkGang* _workers;
145
242 public:
243 enum ScanningOption {
244 SO_None = 0x0,
245 SO_AllCodeCache = 0x8,
246 SO_ScavengeCodeCache = 0x10
247 };
248
249 FlexibleWorkGang* workers() const { return _workers; }
250
251 // Invoke the "do_oop" method the closure "roots" on all root locations.
252 // The "so" argument determines which roots the closure is applied to:
253 // "SO_None" does none;
254 // "SO_AllCodeCache" applies the closure to all elements of the CodeCache.
255 // "SO_ScavengeCodeCache" applies the closure to elements on the scavenge root list in the CodeCache.
256 void process_roots(bool activate_scope,
257 ScanningOption so,
258 OopClosure* strong_roots,
259 OopClosure* weak_roots,
260 CLDClosure* strong_cld_closure,
261 CLDClosure* weak_cld_closure,
262 CodeBlobClosure* code_roots,
263 GCPhaseTimeTracker* phase_durations = NULL);
264 void process_all_roots(bool activate_scope,
265 ScanningOption so,
266 OopClosure* roots,
267 CLDClosure* cld_closure,
268 CodeBlobClosure* code_roots,
269 GCPhaseTimeTracker* phase_durations = NULL);
270 void process_strong_roots(bool activate_scope,
271 ScanningOption so,
272 OopClosure* roots,
273 CLDClosure* cld_closure,
274 CodeBlobClosure* code_roots,
275 GCPhaseTimeTracker* phase_durations = NULL);
276
277
278 // Apply "root_closure" to the JNI weak roots..
279 void process_weak_roots(OopClosure* root_closure);
280
281 // The functions below are helper functions that a subclass of
282 // "SharedHeap" can use in the implementation of its virtual
283 // functions.
284
285 public:
286
287 // Do anything common to GC's.
288 virtual void gc_prologue(bool full) = 0;
289 virtual void gc_epilogue(bool full) = 0;
290
291 // Sets the number of parallel threads that will be doing tasks
292 // (such as process roots) subsequently.
293 virtual void set_par_threads(uint t);
294
295 int n_termination();
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