Tue, 07 Oct 2008 11:01:35 -0700
Merge
1 /*
2 * Copyright 2001-2008 Sun Microsystems, Inc. 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 *
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 # include "incls/_precompiled.incl"
26 # include "incls/_psMarkSweepDecorator.cpp.incl"
28 PSMarkSweepDecorator* PSMarkSweepDecorator::_destination_decorator = NULL;
31 void PSMarkSweepDecorator::set_destination_decorator_tenured() {
32 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
33 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
35 _destination_decorator = heap->old_gen()->object_mark_sweep();
36 }
38 void PSMarkSweepDecorator::set_destination_decorator_perm_gen() {
39 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
40 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
42 _destination_decorator = heap->perm_gen()->object_mark_sweep();
43 }
45 void PSMarkSweepDecorator::advance_destination_decorator() {
46 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
47 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
49 assert(_destination_decorator != NULL, "Sanity");
50 guarantee(_destination_decorator != heap->perm_gen()->object_mark_sweep(), "Cannot advance perm gen decorator");
52 PSMarkSweepDecorator* first = heap->old_gen()->object_mark_sweep();
53 PSMarkSweepDecorator* second = heap->young_gen()->eden_mark_sweep();
54 PSMarkSweepDecorator* third = heap->young_gen()->from_mark_sweep();
55 PSMarkSweepDecorator* fourth = heap->young_gen()->to_mark_sweep();
57 if ( _destination_decorator == first ) {
58 _destination_decorator = second;
59 } else if ( _destination_decorator == second ) {
60 _destination_decorator = third;
61 } else if ( _destination_decorator == third ) {
62 _destination_decorator = fourth;
63 } else {
64 fatal("PSMarkSweep attempting to advance past last compaction area");
65 }
66 }
68 PSMarkSweepDecorator* PSMarkSweepDecorator::destination_decorator() {
69 assert(_destination_decorator != NULL, "Sanity");
71 return _destination_decorator;
72 }
74 // FIX ME FIX ME FIX ME FIX ME!!!!!!!!!
75 // The object forwarding code is duplicated. Factor this out!!!!!
76 //
77 // This method "precompacts" objects inside its space to dest. It places forwarding
78 // pointers into markOops for use by adjust_pointers. If "dest" should overflow, we
79 // finish by compacting into our own space.
81 void PSMarkSweepDecorator::precompact() {
82 // Reset our own compact top.
83 set_compaction_top(space()->bottom());
85 /* We allow some amount of garbage towards the bottom of the space, so
86 * we don't start compacting before there is a significant gain to be made.
87 * Occasionally, we want to ensure a full compaction, which is determined
88 * by the MarkSweepAlwaysCompactCount parameter. This is a significant
89 * performance improvement!
90 */
91 bool skip_dead = ((PSMarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0);
93 ssize_t allowed_deadspace = 0;
94 if (skip_dead) {
95 int ratio = allowed_dead_ratio();
96 allowed_deadspace = (space()->capacity_in_bytes() * ratio / 100) / HeapWordSize;
97 }
99 // Fetch the current destination decorator
100 PSMarkSweepDecorator* dest = destination_decorator();
101 ObjectStartArray* start_array = dest->start_array();
103 HeapWord* compact_top = dest->compaction_top();
104 HeapWord* compact_end = dest->space()->end();
106 HeapWord* q = space()->bottom();
107 HeapWord* t = space()->top();
109 HeapWord* end_of_live= q; /* One byte beyond the last byte of the last
110 live object. */
111 HeapWord* first_dead = space()->end(); /* The first dead object. */
112 LiveRange* liveRange = NULL; /* The current live range, recorded in the
113 first header of preceding free area. */
114 _first_dead = first_dead;
116 const intx interval = PrefetchScanIntervalInBytes;
118 while (q < t) {
119 assert(oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() ||
120 oop(q)->mark()->has_bias_pattern(),
121 "these are the only valid states during a mark sweep");
122 if (oop(q)->is_gc_marked()) {
123 /* prefetch beyond q */
124 Prefetch::write(q, interval);
125 size_t size = oop(q)->size();
127 size_t compaction_max_size = pointer_delta(compact_end, compact_top);
129 // This should only happen if a space in the young gen overflows the
130 // old gen. If that should happen, we null out the start_array, because
131 // the young spaces are not covered by one.
132 while(size > compaction_max_size) {
133 // First record the last compact_top
134 dest->set_compaction_top(compact_top);
136 // Advance to the next compaction decorator
137 advance_destination_decorator();
138 dest = destination_decorator();
140 // Update compaction info
141 start_array = dest->start_array();
142 compact_top = dest->compaction_top();
143 compact_end = dest->space()->end();
144 assert(compact_top == dest->space()->bottom(), "Advanced to space already in use");
145 assert(compact_end > compact_top, "Must always be space remaining");
146 compaction_max_size =
147 pointer_delta(compact_end, compact_top);
148 }
150 // store the forwarding pointer into the mark word
151 if (q != compact_top) {
152 oop(q)->forward_to(oop(compact_top));
153 assert(oop(q)->is_gc_marked(), "encoding the pointer should preserve the mark");
154 } else {
155 // if the object isn't moving we can just set the mark to the default
156 // mark and handle it specially later on.
157 oop(q)->init_mark();
158 assert(oop(q)->forwardee() == NULL, "should be forwarded to NULL");
159 }
161 // Update object start array
162 if (start_array) {
163 start_array->allocate_block(compact_top);
164 }
166 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::register_live_oop(oop(q), size));
167 compact_top += size;
168 assert(compact_top <= dest->space()->end(),
169 "Exceeding space in destination");
171 q += size;
172 end_of_live = q;
173 } else {
174 /* run over all the contiguous dead objects */
175 HeapWord* end = q;
176 do {
177 /* prefetch beyond end */
178 Prefetch::write(end, interval);
179 end += oop(end)->size();
180 } while (end < t && (!oop(end)->is_gc_marked()));
182 /* see if we might want to pretend this object is alive so that
183 * we don't have to compact quite as often.
184 */
185 if (allowed_deadspace > 0 && q == compact_top) {
186 size_t sz = pointer_delta(end, q);
187 if (insert_deadspace(allowed_deadspace, q, sz)) {
188 size_t compaction_max_size = pointer_delta(compact_end, compact_top);
190 // This should only happen if a space in the young gen overflows the
191 // old gen. If that should happen, we null out the start_array, because
192 // the young spaces are not covered by one.
193 while (sz > compaction_max_size) {
194 // First record the last compact_top
195 dest->set_compaction_top(compact_top);
197 // Advance to the next compaction decorator
198 advance_destination_decorator();
199 dest = destination_decorator();
201 // Update compaction info
202 start_array = dest->start_array();
203 compact_top = dest->compaction_top();
204 compact_end = dest->space()->end();
205 assert(compact_top == dest->space()->bottom(), "Advanced to space already in use");
206 assert(compact_end > compact_top, "Must always be space remaining");
207 compaction_max_size =
208 pointer_delta(compact_end, compact_top);
209 }
211 // store the forwarding pointer into the mark word
212 if (q != compact_top) {
213 oop(q)->forward_to(oop(compact_top));
214 assert(oop(q)->is_gc_marked(), "encoding the pointer should preserve the mark");
215 } else {
216 // if the object isn't moving we can just set the mark to the default
217 // mark and handle it specially later on.
218 oop(q)->init_mark();
219 assert(oop(q)->forwardee() == NULL, "should be forwarded to NULL");
220 }
222 // Update object start array
223 if (start_array) {
224 start_array->allocate_block(compact_top);
225 }
227 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::register_live_oop(oop(q), sz));
228 compact_top += sz;
229 assert(compact_top <= dest->space()->end(),
230 "Exceeding space in destination");
232 q = end;
233 end_of_live = end;
234 continue;
235 }
236 }
238 /* for the previous LiveRange, record the end of the live objects. */
239 if (liveRange) {
240 liveRange->set_end(q);
241 }
243 /* record the current LiveRange object.
244 * liveRange->start() is overlaid on the mark word.
245 */
246 liveRange = (LiveRange*)q;
247 liveRange->set_start(end);
248 liveRange->set_end(end);
250 /* see if this is the first dead region. */
251 if (q < first_dead) {
252 first_dead = q;
253 }
255 /* move on to the next object */
256 q = end;
257 }
258 }
260 assert(q == t, "just checking");
261 if (liveRange != NULL) {
262 liveRange->set_end(q);
263 }
264 _end_of_live = end_of_live;
265 if (end_of_live < first_dead) {
266 first_dead = end_of_live;
267 }
268 _first_dead = first_dead;
270 // Update compaction top
271 dest->set_compaction_top(compact_top);
272 }
274 bool PSMarkSweepDecorator::insert_deadspace(ssize_t& allowed_deadspace_words,
275 HeapWord* q, size_t deadlength) {
276 allowed_deadspace_words -= deadlength;
277 if (allowed_deadspace_words >= 0) {
278 oop(q)->set_mark(markOopDesc::prototype()->set_marked());
279 const size_t aligned_min_int_array_size =
280 align_object_size(typeArrayOopDesc::header_size(T_INT));
281 if (deadlength >= aligned_min_int_array_size) {
282 oop(q)->set_klass(Universe::intArrayKlassObj());
283 assert(((deadlength - aligned_min_int_array_size) * (HeapWordSize/sizeof(jint))) < (size_t)max_jint,
284 "deadspace too big for Arrayoop");
285 typeArrayOop(q)->set_length((int)((deadlength - aligned_min_int_array_size)
286 * (HeapWordSize/sizeof(jint))));
287 } else {
288 assert((int) deadlength == instanceOopDesc::header_size(),
289 "size for smallest fake dead object doesn't match");
290 oop(q)->set_klass(SystemDictionary::object_klass());
291 }
292 assert((int) deadlength == oop(q)->size(),
293 "make sure size for fake dead object match");
294 // Recall that we required "q == compaction_top".
295 return true;
296 } else {
297 allowed_deadspace_words = 0;
298 return false;
299 }
300 }
302 void PSMarkSweepDecorator::adjust_pointers() {
303 // adjust all the interior pointers to point at the new locations of objects
304 // Used by MarkSweep::mark_sweep_phase3()
306 HeapWord* q = space()->bottom();
307 HeapWord* t = _end_of_live; // Established by "prepare_for_compaction".
309 assert(_first_dead <= _end_of_live, "Stands to reason, no?");
311 if (q < t && _first_dead > q &&
312 !oop(q)->is_gc_marked()) {
313 // we have a chunk of the space which hasn't moved and we've
314 // reinitialized the mark word during the previous pass, so we can't
315 // use is_gc_marked for the traversal.
316 HeapWord* end = _first_dead;
318 while (q < end) {
319 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q)));
320 // point all the oops to the new location
321 size_t size = oop(q)->adjust_pointers();
322 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers());
323 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size));
324 q += size;
325 }
327 if (_first_dead == t) {
328 q = t;
329 } else {
330 // $$$ This is funky. Using this to read the previously written
331 // LiveRange. See also use below.
332 q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer();
333 }
334 }
335 const intx interval = PrefetchScanIntervalInBytes;
337 debug_only(HeapWord* prev_q = NULL);
338 while (q < t) {
339 // prefetch beyond q
340 Prefetch::write(q, interval);
341 if (oop(q)->is_gc_marked()) {
342 // q is alive
343 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q)));
344 // point all the oops to the new location
345 size_t size = oop(q)->adjust_pointers();
346 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers());
347 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size));
348 debug_only(prev_q = q);
349 q += size;
350 } else {
351 // q is not a live object, so its mark should point at the next
352 // live object
353 debug_only(prev_q = q);
354 q = (HeapWord*) oop(q)->mark()->decode_pointer();
355 assert(q > prev_q, "we should be moving forward through memory");
356 }
357 }
359 assert(q == t, "just checking");
360 }
362 void PSMarkSweepDecorator::compact(bool mangle_free_space ) {
363 // Copy all live objects to their new location
364 // Used by MarkSweep::mark_sweep_phase4()
366 HeapWord* q = space()->bottom();
367 HeapWord* const t = _end_of_live;
368 debug_only(HeapWord* prev_q = NULL);
370 if (q < t && _first_dead > q &&
371 !oop(q)->is_gc_marked()) {
372 #ifdef ASSERT
373 // we have a chunk of the space which hasn't moved and we've reinitialized the
374 // mark word during the previous pass, so we can't use is_gc_marked for the
375 // traversal.
376 HeapWord* const end = _first_dead;
378 while (q < end) {
379 size_t size = oop(q)->size();
380 assert(!oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)");
381 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size, q));
382 debug_only(prev_q = q);
383 q += size;
384 }
385 #endif
387 if (_first_dead == t) {
388 q = t;
389 } else {
390 // $$$ Funky
391 q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer();
392 }
393 }
395 const intx scan_interval = PrefetchScanIntervalInBytes;
396 const intx copy_interval = PrefetchCopyIntervalInBytes;
398 while (q < t) {
399 if (!oop(q)->is_gc_marked()) {
400 // mark is pointer to next marked oop
401 debug_only(prev_q = q);
402 q = (HeapWord*) oop(q)->mark()->decode_pointer();
403 assert(q > prev_q, "we should be moving forward through memory");
404 } else {
405 // prefetch beyond q
406 Prefetch::read(q, scan_interval);
408 // size and destination
409 size_t size = oop(q)->size();
410 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee();
412 // prefetch beyond compaction_top
413 Prefetch::write(compaction_top, copy_interval);
415 // copy object and reinit its mark
416 VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size, compaction_top));
417 assert(q != compaction_top, "everything in this pass should be moving");
418 Copy::aligned_conjoint_words(q, compaction_top, size);
419 oop(compaction_top)->init_mark();
420 assert(oop(compaction_top)->klass() != NULL, "should have a class");
422 debug_only(prev_q = q);
423 q += size;
424 }
425 }
427 assert(compaction_top() >= space()->bottom() && compaction_top() <= space()->end(),
428 "should point inside space");
429 space()->set_top(compaction_top());
431 if (mangle_free_space) {
432 space()->mangle_unused_area();
433 }
434 }