Thu, 22 Sep 2011 10:57:37 -0700
6484982: G1: process references during evacuation pauses
Summary: G1 now uses two reference processors - one is used by concurrent marking and the other is used by STW GCs (both full and incremental evacuation pauses). In an evacuation pause, the reference processor is embedded into the closures used to scan objects. Doing so causes causes reference objects to be 'discovered' by the reference processor. At the end of the evacuation pause, these discovered reference objects are processed - preserving (and copying) referent objects (and their reachable graphs) as appropriate.
Reviewed-by: ysr, jwilhelm, brutisso, stefank, tonyp
1 /*
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25 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PCTASKS_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PCTASKS_HPP
28 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
29 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
30 #include "gc_implementation/parallelScavenge/psTasks.hpp"
33 // Tasks for parallel compaction of the old generation
34 //
35 // Tasks are created and enqueued on a task queue. The
36 // tasks for parallel old collector for marking objects
37 // are MarkFromRootsTask and ThreadRootsMarkingTask.
38 //
39 // MarkFromRootsTask's are created
40 // with a root group (e.g., jni_handles) and when the do_it()
41 // method of a MarkFromRootsTask is executed, it starts marking
42 // form it's root group.
43 //
44 // ThreadRootsMarkingTask's are created for each Java thread. When
45 // the do_it() method of a ThreadRootsMarkingTask is executed, it
46 // starts marking from the thread's roots.
47 //
48 // The enqueuing of the MarkFromRootsTask and ThreadRootsMarkingTask
49 // do little more than create the task and put it on a queue. The
50 // queue is a GCTaskQueue and threads steal tasks from this GCTaskQueue.
51 //
52 // In addition to the MarkFromRootsTask and ThreadRootsMarkingTask
53 // tasks there are StealMarkingTask tasks. The StealMarkingTask's
54 // steal a reference from the marking stack of another
55 // thread and transitively marks the object of the reference
56 // and internal references. After successfully stealing a reference
57 // and marking it, the StealMarkingTask drains its marking stack
58 // stack before attempting another steal.
59 //
60 // ThreadRootsMarkingTask
61 //
62 // This task marks from the roots of a single thread. This task
63 // enables marking of thread roots in parallel.
64 //
66 class ParallelTaskTerminator;
68 class ThreadRootsMarkingTask : public GCTask {
69 private:
70 JavaThread* _java_thread;
71 VMThread* _vm_thread;
72 public:
73 ThreadRootsMarkingTask(JavaThread* root) : _java_thread(root), _vm_thread(NULL) {}
74 ThreadRootsMarkingTask(VMThread* root) : _java_thread(NULL), _vm_thread(root) {}
76 char* name() { return (char *)"thread-roots-marking-task"; }
78 virtual void do_it(GCTaskManager* manager, uint which);
79 };
82 //
83 // MarkFromRootsTask
84 //
85 // This task marks from all the roots to all live
86 // objects.
87 //
88 //
90 class MarkFromRootsTask : public GCTask {
91 public:
92 enum RootType {
93 universe = 1,
94 jni_handles = 2,
95 threads = 3,
96 object_synchronizer = 4,
97 flat_profiler = 5,
98 management = 6,
99 jvmti = 7,
100 system_dictionary = 8,
101 code_cache = 9
102 };
103 private:
104 RootType _root_type;
105 public:
106 MarkFromRootsTask(RootType value) : _root_type(value) {}
108 char* name() { return (char *)"mark-from-roots-task"; }
110 virtual void do_it(GCTaskManager* manager, uint which);
111 };
113 //
114 // RefProcTaskProxy
115 //
116 // This task is used as a proxy to parallel reference processing tasks .
117 //
119 class RefProcTaskProxy : public GCTask {
120 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
121 ProcessTask & _rp_task;
122 uint _work_id;
123 public:
124 RefProcTaskProxy(ProcessTask & rp_task, uint work_id)
125 : _rp_task(rp_task),
126 _work_id(work_id)
127 { }
129 private:
130 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
132 virtual void do_it(GCTaskManager* manager, uint which);
133 };
137 //
138 // RefEnqueueTaskProxy
139 //
140 // This task is used as a proxy to parallel reference processing tasks .
141 //
143 class RefEnqueueTaskProxy: public GCTask {
144 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
145 EnqueueTask& _enq_task;
146 uint _work_id;
148 public:
149 RefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
150 : _enq_task(enq_task),
151 _work_id(work_id)
152 { }
154 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
155 virtual void do_it(GCTaskManager* manager, uint which)
156 {
157 _enq_task.work(_work_id);
158 }
159 };
162 //
163 // RefProcTaskExecutor
164 //
165 // Task executor is an interface for the reference processor to run
166 // tasks using GCTaskManager.
167 //
169 class RefProcTaskExecutor: public AbstractRefProcTaskExecutor {
170 virtual void execute(ProcessTask& task);
171 virtual void execute(EnqueueTask& task);
172 };
175 //
176 // StealMarkingTask
177 //
178 // This task is used to distribute work to idle threads.
179 //
181 class StealMarkingTask : public GCTask {
182 private:
183 ParallelTaskTerminator* const _terminator;
184 private:
186 public:
187 char* name() { return (char *)"steal-marking-task"; }
189 StealMarkingTask(ParallelTaskTerminator* t);
191 ParallelTaskTerminator* terminator() { return _terminator; }
193 virtual void do_it(GCTaskManager* manager, uint which);
194 };
196 //
197 // StealRegionCompactionTask
198 //
199 // This task is used to distribute work to idle threads.
200 //
202 class StealRegionCompactionTask : public GCTask {
203 private:
204 ParallelTaskTerminator* const _terminator;
205 public:
206 StealRegionCompactionTask(ParallelTaskTerminator* t);
208 char* name() { return (char *)"steal-region-task"; }
209 ParallelTaskTerminator* terminator() { return _terminator; }
211 virtual void do_it(GCTaskManager* manager, uint which);
212 };
214 //
215 // UpdateDensePrefixTask
216 //
217 // This task is used to update the dense prefix
218 // of a space.
219 //
221 class UpdateDensePrefixTask : public GCTask {
222 private:
223 PSParallelCompact::SpaceId _space_id;
224 size_t _region_index_start;
225 size_t _region_index_end;
227 public:
228 char* name() { return (char *)"update-dense_prefix-task"; }
230 UpdateDensePrefixTask(PSParallelCompact::SpaceId space_id,
231 size_t region_index_start,
232 size_t region_index_end);
234 virtual void do_it(GCTaskManager* manager, uint which);
235 };
237 //
238 // DrainStacksCompactionTask
239 //
240 // This task processes regions that have been added to the stacks of each
241 // compaction manager.
242 //
243 // Trying to use one draining thread does not work because there are no
244 // guarantees about which task will be picked up by which thread. For example,
245 // if thread A gets all the preloaded regions, thread A may not get a draining
246 // task (they may all be done by other threads).
247 //
249 class DrainStacksCompactionTask : public GCTask {
250 uint _stack_index;
251 uint stack_index() { return _stack_index; }
252 public:
253 DrainStacksCompactionTask(uint stack_index) : GCTask(),
254 _stack_index(stack_index) {};
255 char* name() { return (char *)"drain-region-task"; }
256 virtual void do_it(GCTaskManager* manager, uint which);
257 };
259 #endif // SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PCTASKS_HPP