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_G1_BUFFERINGOOPCLOSURE_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_BUFFERINGOOPCLOSURE_HPP
28 #include "memory/genOopClosures.hpp"
29 #include "memory/generation.hpp"
30 #include "runtime/os.hpp"
31 #include "utilities/taskqueue.hpp"
33 // A BufferingOops closure tries to separate out the cost of finding roots
34 // from the cost of applying closures to them. It maintains an array of
35 // ref-containing locations. Until the array is full, applying the closure
36 // to an oop* merely records that location in the array. Since this
37 // closure app cost is small, an elapsed timer can approximately attribute
38 // all of this cost to the cost of finding the roots. When the array fills
39 // up, the wrapped closure is applied to all elements, keeping track of
40 // this elapsed time of this process, and leaving the array empty.
41 // The caller must be sure to call "done" to process any unprocessed
42 // buffered entriess.
44 class Generation;
45 class HeapRegion;
47 class BufferingOopClosure: public OopClosure {
48 protected:
49 enum PrivateConstants {
50 BufferLength = 1024
51 };
53 StarTask _buffer[BufferLength];
54 StarTask* _buffer_top;
55 StarTask* _buffer_curr;
57 OopClosure* _oc;
58 double _closure_app_seconds;
60 void process_buffer () {
61 double start = os::elapsedTime();
62 for (StarTask* curr = _buffer; curr < _buffer_curr; ++curr) {
63 if (curr->is_narrow()) {
64 assert(UseCompressedOops, "Error");
65 _oc->do_oop((narrowOop*)(*curr));
66 } else {
67 _oc->do_oop((oop*)(*curr));
68 }
69 }
70 _buffer_curr = _buffer;
71 _closure_app_seconds += (os::elapsedTime() - start);
72 }
74 template <class T> inline void do_oop_work(T* p) {
75 if (_buffer_curr == _buffer_top) {
76 process_buffer();
77 }
78 StarTask new_ref(p);
79 *_buffer_curr = new_ref;
80 ++_buffer_curr;
81 }
83 public:
84 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
85 virtual void do_oop(oop* p) { do_oop_work(p); }
87 void done () {
88 if (_buffer_curr > _buffer) {
89 process_buffer();
90 }
91 }
92 double closure_app_seconds () {
93 return _closure_app_seconds;
94 }
95 BufferingOopClosure (OopClosure *oc) :
96 _oc(oc),
97 _buffer_curr(_buffer), _buffer_top(_buffer + BufferLength),
98 _closure_app_seconds(0.0) { }
99 };
101 class BufferingOopsInGenClosure: public OopsInGenClosure {
102 BufferingOopClosure _boc;
103 OopsInGenClosure* _oc;
104 protected:
105 template <class T> inline void do_oop_work(T* p) {
106 assert(generation()->is_in_reserved((void*)p), "Must be in!");
107 _boc.do_oop(p);
108 }
109 public:
110 BufferingOopsInGenClosure(OopsInGenClosure *oc) :
111 _boc(oc), _oc(oc) {}
113 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
114 virtual void do_oop(oop* p) { do_oop_work(p); }
116 void done() {
117 _boc.done();
118 }
120 double closure_app_seconds () {
121 return _boc.closure_app_seconds();
122 }
124 void set_generation(Generation* gen) {
125 OopsInGenClosure::set_generation(gen);
126 _oc->set_generation(gen);
127 }
129 void reset_generation() {
130 // Make sure we finish the current work with the current generation.
131 _boc.done();
132 OopsInGenClosure::reset_generation();
133 _oc->reset_generation();
134 }
136 };
139 class BufferingOopsInHeapRegionClosure: public OopsInHeapRegionClosure {
140 private:
141 enum PrivateConstants {
142 BufferLength = 1024
143 };
145 StarTask _buffer[BufferLength];
146 StarTask* _buffer_top;
147 StarTask* _buffer_curr;
149 HeapRegion* _hr_buffer[BufferLength];
150 HeapRegion** _hr_curr;
152 OopsInHeapRegionClosure* _oc;
153 double _closure_app_seconds;
155 void process_buffer () {
157 assert((_hr_curr - _hr_buffer) == (_buffer_curr - _buffer),
158 "the two lengths should be the same");
160 double start = os::elapsedTime();
161 HeapRegion** hr_curr = _hr_buffer;
162 HeapRegion* hr_prev = NULL;
163 for (StarTask* curr = _buffer; curr < _buffer_curr; ++curr) {
164 HeapRegion* region = *hr_curr;
165 if (region != hr_prev) {
166 _oc->set_region(region);
167 hr_prev = region;
168 }
169 if (curr->is_narrow()) {
170 assert(UseCompressedOops, "Error");
171 _oc->do_oop((narrowOop*)(*curr));
172 } else {
173 _oc->do_oop((oop*)(*curr));
174 }
175 ++hr_curr;
176 }
177 _buffer_curr = _buffer;
178 _hr_curr = _hr_buffer;
179 _closure_app_seconds += (os::elapsedTime() - start);
180 }
182 public:
183 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
184 virtual void do_oop( oop* p) { do_oop_work(p); }
186 template <class T> void do_oop_work(T* p) {
187 if (_buffer_curr == _buffer_top) {
188 assert(_hr_curr > _hr_buffer, "_hr_curr should be consistent with _buffer_curr");
189 process_buffer();
190 }
191 StarTask new_ref(p);
192 *_buffer_curr = new_ref;
193 ++_buffer_curr;
194 *_hr_curr = _from;
195 ++_hr_curr;
196 }
197 void done () {
198 if (_buffer_curr > _buffer) {
199 assert(_hr_curr > _hr_buffer, "_hr_curr should be consistent with _buffer_curr");
200 process_buffer();
201 }
202 }
203 double closure_app_seconds () {
204 return _closure_app_seconds;
205 }
206 BufferingOopsInHeapRegionClosure (OopsInHeapRegionClosure *oc) :
207 _oc(oc),
208 _buffer_curr(_buffer), _buffer_top(_buffer + BufferLength),
209 _hr_curr(_hr_buffer),
210 _closure_app_seconds(0.0) { }
211 };
213 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_BUFFERINGOOPCLOSURE_HPP