Mercurial > hg > truffle
annotate src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.cpp @ 1972:f95d63e2154a
6989984: Use standard include model for Hospot
Summary: Replaced MakeDeps and the includeDB files with more standardized solutions.
Reviewed-by: coleenp, kvn, kamg
| author | stefank |
|---|---|
| date | Tue, 23 Nov 2010 13:22:55 -0800 |
| parents | 9d7a8ab3736b |
| children | bca17e38de00 |
| rev | line source |
|---|---|
| 0 | 1 /* |
|
1612
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved. |
| 0 | 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 * | |
|
1552
c18cbe5936b8
6941466: Oracle rebranding changes for Hotspot repositories
trims
parents:
605
diff
changeset
|
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
|
c18cbe5936b8
6941466: Oracle rebranding changes for Hotspot repositories
trims
parents:
605
diff
changeset
|
20 * or visit www.oracle.com if you need additional information or have any |
|
c18cbe5936b8
6941466: Oracle rebranding changes for Hotspot repositories
trims
parents:
605
diff
changeset
|
21 * questions. |
| 0 | 22 * |
| 23 */ | |
| 24 | |
| 1972 | 25 #include "precompiled.hpp" |
| 26 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp" | |
| 27 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp" | |
| 28 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp" | |
| 29 #include "gc_implementation/parallelScavenge/psTasks.hpp" | |
| 30 #include "gc_implementation/parallelScavenge/psYoungGen.hpp" | |
| 31 #include "oops/oop.inline.hpp" | |
| 32 #include "oops/oop.psgc.inline.hpp" | |
| 0 | 33 |
| 34 // Checks an individual oop for missing precise marks. Mark | |
| 35 // may be either dirty or newgen. | |
| 36 class CheckForUnmarkedOops : public OopClosure { | |
|
113
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
37 private: |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
38 PSYoungGen* _young_gen; |
| 0 | 39 CardTableExtension* _card_table; |
|
113
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
40 HeapWord* _unmarked_addr; |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
41 jbyte* _unmarked_card; |
| 0 | 42 |
|
113
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
43 protected: |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
44 template <class T> void do_oop_work(T* p) { |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
45 oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
46 if (_young_gen->is_in_reserved(obj) && |
| 0 | 47 !_card_table->addr_is_marked_imprecise(p)) { |
| 48 // Don't overwrite the first missing card mark | |
| 49 if (_unmarked_addr == NULL) { | |
| 50 _unmarked_addr = (HeapWord*)p; | |
| 51 _unmarked_card = _card_table->byte_for(p); | |
| 52 } | |
| 53 } | |
| 54 } | |
| 55 | |
|
113
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
56 public: |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
57 CheckForUnmarkedOops(PSYoungGen* young_gen, CardTableExtension* card_table) : |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
58 _young_gen(young_gen), _card_table(card_table), _unmarked_addr(NULL) { } |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
59 |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
60 virtual void do_oop(oop* p) { CheckForUnmarkedOops::do_oop_work(p); } |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
61 virtual void do_oop(narrowOop* p) { CheckForUnmarkedOops::do_oop_work(p); } |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
62 |
| 0 | 63 bool has_unmarked_oop() { |
| 64 return _unmarked_addr != NULL; | |
| 65 } | |
| 66 }; | |
| 67 | |
| 68 // Checks all objects for the existance of some type of mark, | |
| 69 // precise or imprecise, dirty or newgen. | |
| 70 class CheckForUnmarkedObjects : public ObjectClosure { | |
|
113
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
71 private: |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
72 PSYoungGen* _young_gen; |
| 0 | 73 CardTableExtension* _card_table; |
| 74 | |
| 75 public: | |
| 76 CheckForUnmarkedObjects() { | |
| 77 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); | |
| 78 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); | |
| 79 | |
| 80 _young_gen = heap->young_gen(); | |
| 81 _card_table = (CardTableExtension*)heap->barrier_set(); | |
| 82 // No point in asserting barrier set type here. Need to make CardTableExtension | |
| 83 // a unique barrier set type. | |
| 84 } | |
| 85 | |
| 86 // Card marks are not precise. The current system can leave us with | |
| 605 | 87 // a mismash of precise marks and beginning of object marks. This means |
| 0 | 88 // we test for missing precise marks first. If any are found, we don't |
| 89 // fail unless the object head is also unmarked. | |
| 90 virtual void do_object(oop obj) { | |
|
113
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
91 CheckForUnmarkedOops object_check(_young_gen, _card_table); |
| 0 | 92 obj->oop_iterate(&object_check); |
| 93 if (object_check.has_unmarked_oop()) { | |
| 94 assert(_card_table->addr_is_marked_imprecise(obj), "Found unmarked young_gen object"); | |
| 95 } | |
| 96 } | |
| 97 }; | |
| 98 | |
| 99 // Checks for precise marking of oops as newgen. | |
| 100 class CheckForPreciseMarks : public OopClosure { | |
|
113
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
101 private: |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
102 PSYoungGen* _young_gen; |
| 0 | 103 CardTableExtension* _card_table; |
| 104 | |
|
113
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
105 protected: |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
106 template <class T> void do_oop_work(T* p) { |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
107 oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
108 if (_young_gen->is_in_reserved(obj)) { |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
109 assert(_card_table->addr_is_marked_precise(p), "Found unmarked precise oop"); |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
110 _card_table->set_card_newgen(p); |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
111 } |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
112 } |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
113 |
| 0 | 114 public: |
| 115 CheckForPreciseMarks( PSYoungGen* young_gen, CardTableExtension* card_table ) : | |
| 116 _young_gen(young_gen), _card_table(card_table) { } | |
| 117 | |
|
113
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
118 virtual void do_oop(oop* p) { CheckForPreciseMarks::do_oop_work(p); } |
|
ba764ed4b6f2
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes
coleenp
parents:
0
diff
changeset
|
119 virtual void do_oop(narrowOop* p) { CheckForPreciseMarks::do_oop_work(p); } |
| 0 | 120 }; |
| 121 | |
| 122 // We get passed the space_top value to prevent us from traversing into | |
| 123 // the old_gen promotion labs, which cannot be safely parsed. | |
| 124 void CardTableExtension::scavenge_contents(ObjectStartArray* start_array, | |
| 125 MutableSpace* sp, | |
| 126 HeapWord* space_top, | |
| 127 PSPromotionManager* pm) | |
| 128 { | |
| 129 assert(start_array != NULL && sp != NULL && pm != NULL, "Sanity"); | |
| 130 assert(start_array->covered_region().contains(sp->used_region()), | |
| 131 "ObjectStartArray does not cover space"); | |
| 132 | |
| 133 if (sp->not_empty()) { | |
| 134 oop* sp_top = (oop*)space_top; | |
| 135 oop* prev_top = NULL; | |
| 136 jbyte* current_card = byte_for(sp->bottom()); | |
| 137 jbyte* end_card = byte_for(sp_top - 1); // sp_top is exclusive | |
| 138 // scan card marking array | |
| 139 while (current_card <= end_card) { | |
| 140 jbyte value = *current_card; | |
| 141 // skip clean cards | |
| 142 if (card_is_clean(value)) { | |
| 143 current_card++; | |
| 144 } else { | |
| 145 // we found a non-clean card | |
| 146 jbyte* first_nonclean_card = current_card++; | |
| 147 oop* bottom = (oop*)addr_for(first_nonclean_card); | |
| 148 // find object starting on card | |
| 149 oop* bottom_obj = (oop*)start_array->object_start((HeapWord*)bottom); | |
| 150 // bottom_obj = (oop*)start_array->object_start((HeapWord*)bottom); | |
| 151 assert(bottom_obj <= bottom, "just checking"); | |
| 152 // make sure we don't scan oops we already looked at | |
| 153 if (bottom < prev_top) bottom = prev_top; | |
| 154 // figure out when to stop scanning | |
| 155 jbyte* first_clean_card; | |
| 156 oop* top; | |
| 157 bool restart_scanning; | |
| 158 do { | |
| 159 restart_scanning = false; | |
| 160 // find a clean card | |
| 161 while (current_card <= end_card) { | |
| 162 value = *current_card; | |
| 163 if (card_is_clean(value)) break; | |
| 164 current_card++; | |
| 165 } | |
| 166 // check if we reached the end, if so we are done | |
| 167 if (current_card >= end_card) { | |
| 168 first_clean_card = end_card + 1; | |
| 169 current_card++; | |
| 170 top = sp_top; | |
| 171 } else { | |
| 172 // we have a clean card, find object starting on that card | |
| 173 first_clean_card = current_card++; | |
| 174 top = (oop*)addr_for(first_clean_card); | |
| 175 oop* top_obj = (oop*)start_array->object_start((HeapWord*)top); | |
| 176 // top_obj = (oop*)start_array->object_start((HeapWord*)top); | |
| 177 assert(top_obj <= top, "just checking"); | |
| 178 if (oop(top_obj)->is_objArray() || oop(top_obj)->is_typeArray()) { | |
| 179 // an arrayOop is starting on the clean card - since we do exact store | |
| 180 // checks for objArrays we are done | |
| 181 } else { | |
| 182 // otherwise, it is possible that the object starting on the clean card | |
| 183 // spans the entire card, and that the store happened on a later card. | |
| 184 // figure out where the object ends | |
| 185 top = top_obj + oop(top_obj)->size(); | |
| 186 jbyte* top_card = CardTableModRefBS::byte_for(top - 1); // top is exclusive | |
| 187 if (top_card > first_clean_card) { | |
| 188 // object ends a different card | |
| 189 current_card = top_card + 1; | |
| 190 if (card_is_clean(*top_card)) { | |
| 191 // the ending card is clean, we are done | |
| 192 first_clean_card = top_card; | |
| 193 } else { | |
| 194 // the ending card is not clean, continue scanning at start of do-while | |
| 195 restart_scanning = true; | |
| 196 } | |
| 197 } else { | |
| 198 // object ends on the clean card, we are done. | |
| 199 assert(first_clean_card == top_card, "just checking"); | |
| 200 } | |
| 201 } | |
| 202 } | |
| 203 } while (restart_scanning); | |
| 204 // we know which cards to scan, now clear them | |
| 205 while (first_nonclean_card < first_clean_card) { | |
| 206 *first_nonclean_card++ = clean_card; | |
| 207 } | |
| 208 // scan oops in objects | |
|
1706
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
209 do { |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
210 oop(bottom_obj)->push_contents(pm); |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
211 bottom_obj += oop(bottom_obj)->size(); |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
212 assert(bottom_obj <= sp_top, "just checking"); |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
213 } while (bottom_obj < top); |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
214 pm->drain_stacks_cond_depth(); |
| 0 | 215 // remember top oop* scanned |
| 216 prev_top = top; | |
| 217 } | |
| 218 } | |
| 219 } | |
| 220 } | |
| 221 | |
| 222 void CardTableExtension::scavenge_contents_parallel(ObjectStartArray* start_array, | |
| 223 MutableSpace* sp, | |
| 224 HeapWord* space_top, | |
| 225 PSPromotionManager* pm, | |
| 226 uint stripe_number) { | |
| 227 int ssize = 128; // Naked constant! Work unit = 64k. | |
| 228 int dirty_card_count = 0; | |
| 229 | |
| 230 oop* sp_top = (oop*)space_top; | |
| 231 jbyte* start_card = byte_for(sp->bottom()); | |
| 232 jbyte* end_card = byte_for(sp_top - 1) + 1; | |
| 233 oop* last_scanned = NULL; // Prevent scanning objects more than once | |
| 234 for (jbyte* slice = start_card; slice < end_card; slice += ssize*ParallelGCThreads) { | |
| 235 jbyte* worker_start_card = slice + stripe_number * ssize; | |
| 236 if (worker_start_card >= end_card) | |
| 237 return; // We're done. | |
| 238 | |
| 239 jbyte* worker_end_card = worker_start_card + ssize; | |
| 240 if (worker_end_card > end_card) | |
| 241 worker_end_card = end_card; | |
| 242 | |
| 243 // We do not want to scan objects more than once. In order to accomplish | |
| 244 // this, we assert that any object with an object head inside our 'slice' | |
| 245 // belongs to us. We may need to extend the range of scanned cards if the | |
| 246 // last object continues into the next 'slice'. | |
| 247 // | |
| 248 // Note! ending cards are exclusive! | |
| 249 HeapWord* slice_start = addr_for(worker_start_card); | |
| 250 HeapWord* slice_end = MIN2((HeapWord*) sp_top, addr_for(worker_end_card)); | |
| 251 | |
| 252 // If there are not objects starting within the chunk, skip it. | |
| 253 if (!start_array->object_starts_in_range(slice_start, slice_end)) { | |
| 254 continue; | |
| 255 } | |
| 605 | 256 // Update our beginning addr |
| 0 | 257 HeapWord* first_object = start_array->object_start(slice_start); |
| 258 debug_only(oop* first_object_within_slice = (oop*) first_object;) | |
| 259 if (first_object < slice_start) { | |
| 260 last_scanned = (oop*)(first_object + oop(first_object)->size()); | |
| 261 debug_only(first_object_within_slice = last_scanned;) | |
| 262 worker_start_card = byte_for(last_scanned); | |
| 263 } | |
| 264 | |
| 265 // Update the ending addr | |
| 266 if (slice_end < (HeapWord*)sp_top) { | |
| 267 // The subtraction is important! An object may start precisely at slice_end. | |
| 268 HeapWord* last_object = start_array->object_start(slice_end - 1); | |
| 269 slice_end = last_object + oop(last_object)->size(); | |
| 270 // worker_end_card is exclusive, so bump it one past the end of last_object's | |
| 271 // covered span. | |
| 272 worker_end_card = byte_for(slice_end) + 1; | |
| 273 | |
| 274 if (worker_end_card > end_card) | |
| 275 worker_end_card = end_card; | |
| 276 } | |
| 277 | |
| 278 assert(slice_end <= (HeapWord*)sp_top, "Last object in slice crosses space boundary"); | |
| 279 assert(is_valid_card_address(worker_start_card), "Invalid worker start card"); | |
| 280 assert(is_valid_card_address(worker_end_card), "Invalid worker end card"); | |
| 281 // Note that worker_start_card >= worker_end_card is legal, and happens when | |
| 282 // an object spans an entire slice. | |
| 283 assert(worker_start_card <= end_card, "worker start card beyond end card"); | |
| 284 assert(worker_end_card <= end_card, "worker end card beyond end card"); | |
| 285 | |
| 286 jbyte* current_card = worker_start_card; | |
| 287 while (current_card < worker_end_card) { | |
| 288 // Find an unclean card. | |
| 289 while (current_card < worker_end_card && card_is_clean(*current_card)) { | |
| 290 current_card++; | |
| 291 } | |
| 292 jbyte* first_unclean_card = current_card; | |
| 293 | |
| 294 // Find the end of a run of contiguous unclean cards | |
| 295 while (current_card < worker_end_card && !card_is_clean(*current_card)) { | |
| 296 while (current_card < worker_end_card && !card_is_clean(*current_card)) { | |
| 297 current_card++; | |
| 298 } | |
| 299 | |
| 300 if (current_card < worker_end_card) { | |
| 301 // Some objects may be large enough to span several cards. If such | |
| 302 // an object has more than one dirty card, separated by a clean card, | |
| 303 // we will attempt to scan it twice. The test against "last_scanned" | |
| 304 // prevents the redundant object scan, but it does not prevent newly | |
| 305 // marked cards from being cleaned. | |
| 306 HeapWord* last_object_in_dirty_region = start_array->object_start(addr_for(current_card)-1); | |
| 307 size_t size_of_last_object = oop(last_object_in_dirty_region)->size(); | |
| 308 HeapWord* end_of_last_object = last_object_in_dirty_region + size_of_last_object; | |
| 309 jbyte* ending_card_of_last_object = byte_for(end_of_last_object); | |
| 310 assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card"); | |
| 311 if (ending_card_of_last_object > current_card) { | |
| 312 // This means the object spans the next complete card. | |
| 313 // We need to bump the current_card to ending_card_of_last_object | |
| 314 current_card = ending_card_of_last_object; | |
| 315 } | |
| 316 } | |
| 317 } | |
| 318 jbyte* following_clean_card = current_card; | |
| 319 | |
| 320 if (first_unclean_card < worker_end_card) { | |
| 321 oop* p = (oop*) start_array->object_start(addr_for(first_unclean_card)); | |
| 322 assert((HeapWord*)p <= addr_for(first_unclean_card), "checking"); | |
| 323 // "p" should always be >= "last_scanned" because newly GC dirtied | |
| 324 // cards are no longer scanned again (see comment at end | |
| 325 // of loop on the increment of "current_card"). Test that | |
| 326 // hypothesis before removing this code. | |
| 327 // If this code is removed, deal with the first time through | |
| 328 // the loop when the last_scanned is the object starting in | |
| 329 // the previous slice. | |
| 330 assert((p >= last_scanned) || | |
| 331 (last_scanned == first_object_within_slice), | |
| 332 "Should no longer be possible"); | |
| 333 if (p < last_scanned) { | |
| 334 // Avoid scanning more than once; this can happen because | |
| 335 // newgen cards set by GC may a different set than the | |
| 336 // originally dirty set | |
| 337 p = last_scanned; | |
| 338 } | |
| 339 oop* to = (oop*)addr_for(following_clean_card); | |
| 340 | |
| 341 // Test slice_end first! | |
| 342 if ((HeapWord*)to > slice_end) { | |
| 343 to = (oop*)slice_end; | |
| 344 } else if (to > sp_top) { | |
| 345 to = sp_top; | |
| 346 } | |
| 347 | |
| 348 // we know which cards to scan, now clear them | |
| 349 if (first_unclean_card <= worker_start_card+1) | |
| 350 first_unclean_card = worker_start_card+1; | |
| 351 if (following_clean_card >= worker_end_card-1) | |
| 352 following_clean_card = worker_end_card-1; | |
| 353 | |
| 354 while (first_unclean_card < following_clean_card) { | |
| 355 *first_unclean_card++ = clean_card; | |
| 356 } | |
| 357 | |
| 358 const int interval = PrefetchScanIntervalInBytes; | |
| 359 // scan all objects in the range | |
| 360 if (interval != 0) { | |
|
1706
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
361 while (p < to) { |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
362 Prefetch::write(p, interval); |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
363 oop m = oop(p); |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
364 assert(m->is_oop_or_null(), "check for header"); |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
365 m->push_contents(pm); |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
366 p += m->size(); |
| 0 | 367 } |
|
1706
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
368 pm->drain_stacks_cond_depth(); |
| 0 | 369 } else { |
|
1706
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
370 while (p < to) { |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
371 oop m = oop(p); |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
372 assert(m->is_oop_or_null(), "check for header"); |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
373 m->push_contents(pm); |
|
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
374 p += m->size(); |
| 0 | 375 } |
|
1706
9d7a8ab3736b
6962589: remove breadth first scanning code from parallel gc
tonyp
parents:
1612
diff
changeset
|
376 pm->drain_stacks_cond_depth(); |
| 0 | 377 } |
| 378 last_scanned = p; | |
| 379 } | |
| 380 // "current_card" is still the "following_clean_card" or | |
| 381 // the current_card is >= the worker_end_card so the | |
| 382 // loop will not execute again. | |
| 383 assert((current_card == following_clean_card) || | |
| 384 (current_card >= worker_end_card), | |
| 385 "current_card should only be incremented if it still equals " | |
| 386 "following_clean_card"); | |
| 387 // Increment current_card so that it is not processed again. | |
| 388 // It may now be dirty because a old-to-young pointer was | |
| 389 // found on it an updated. If it is now dirty, it cannot be | |
| 390 // be safely cleaned in the next iteration. | |
| 391 current_card++; | |
| 392 } | |
| 393 } | |
| 394 } | |
| 395 | |
| 396 // This should be called before a scavenge. | |
| 397 void CardTableExtension::verify_all_young_refs_imprecise() { | |
| 398 CheckForUnmarkedObjects check; | |
| 399 | |
| 400 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); | |
| 401 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); | |
| 402 | |
| 403 PSOldGen* old_gen = heap->old_gen(); | |
| 404 PSPermGen* perm_gen = heap->perm_gen(); | |
| 405 | |
| 406 old_gen->object_iterate(&check); | |
| 407 perm_gen->object_iterate(&check); | |
| 408 } | |
| 409 | |
| 410 // This should be called immediately after a scavenge, before mutators resume. | |
| 411 void CardTableExtension::verify_all_young_refs_precise() { | |
| 412 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); | |
| 413 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); | |
| 414 | |
| 415 PSOldGen* old_gen = heap->old_gen(); | |
| 416 PSPermGen* perm_gen = heap->perm_gen(); | |
| 417 | |
| 418 CheckForPreciseMarks check(heap->young_gen(), (CardTableExtension*)heap->barrier_set()); | |
| 419 | |
| 420 old_gen->oop_iterate(&check); | |
| 421 perm_gen->oop_iterate(&check); | |
| 422 | |
| 423 verify_all_young_refs_precise_helper(old_gen->object_space()->used_region()); | |
| 424 verify_all_young_refs_precise_helper(perm_gen->object_space()->used_region()); | |
| 425 } | |
| 426 | |
| 427 void CardTableExtension::verify_all_young_refs_precise_helper(MemRegion mr) { | |
| 428 CardTableExtension* card_table = (CardTableExtension*)Universe::heap()->barrier_set(); | |
| 429 // FIX ME ASSERT HERE | |
| 430 | |
| 431 jbyte* bot = card_table->byte_for(mr.start()); | |
| 432 jbyte* top = card_table->byte_for(mr.end()); | |
| 433 while(bot <= top) { | |
| 434 assert(*bot == clean_card || *bot == verify_card, "Found unwanted or unknown card mark"); | |
| 435 if (*bot == verify_card) | |
| 436 *bot = youngergen_card; | |
| 437 bot++; | |
| 438 } | |
| 439 } | |
| 440 | |
| 441 bool CardTableExtension::addr_is_marked_imprecise(void *addr) { | |
| 442 jbyte* p = byte_for(addr); | |
| 443 jbyte val = *p; | |
| 444 | |
| 445 if (card_is_dirty(val)) | |
| 446 return true; | |
| 447 | |
| 448 if (card_is_newgen(val)) | |
| 449 return true; | |
| 450 | |
| 451 if (card_is_clean(val)) | |
| 452 return false; | |
| 453 | |
| 454 assert(false, "Found unhandled card mark type"); | |
| 455 | |
| 456 return false; | |
| 457 } | |
| 458 | |
| 459 // Also includes verify_card | |
| 460 bool CardTableExtension::addr_is_marked_precise(void *addr) { | |
| 461 jbyte* p = byte_for(addr); | |
| 462 jbyte val = *p; | |
| 463 | |
| 464 if (card_is_newgen(val)) | |
| 465 return true; | |
| 466 | |
| 467 if (card_is_verify(val)) | |
| 468 return true; | |
| 469 | |
| 470 if (card_is_clean(val)) | |
| 471 return false; | |
| 472 | |
| 473 if (card_is_dirty(val)) | |
| 474 return false; | |
| 475 | |
| 476 assert(false, "Found unhandled card mark type"); | |
| 477 | |
| 478 return false; | |
| 479 } | |
| 480 | |
| 481 // Assumes that only the base or the end changes. This allows indentification | |
| 482 // of the region that is being resized. The | |
| 483 // CardTableModRefBS::resize_covered_region() is used for the normal case | |
| 484 // where the covered regions are growing or shrinking at the high end. | |
| 485 // The method resize_covered_region_by_end() is analogous to | |
| 486 // CardTableModRefBS::resize_covered_region() but | |
| 487 // for regions that grow or shrink at the low end. | |
| 488 void CardTableExtension::resize_covered_region(MemRegion new_region) { | |
| 489 | |
| 490 for (int i = 0; i < _cur_covered_regions; i++) { | |
| 491 if (_covered[i].start() == new_region.start()) { | |
| 492 // Found a covered region with the same start as the | |
| 493 // new region. The region is growing or shrinking | |
| 494 // from the start of the region. | |
| 495 resize_covered_region_by_start(new_region); | |
| 496 return; | |
| 497 } | |
| 498 if (_covered[i].start() > new_region.start()) { | |
| 499 break; | |
| 500 } | |
| 501 } | |
| 502 | |
| 503 int changed_region = -1; | |
| 504 for (int j = 0; j < _cur_covered_regions; j++) { | |
| 505 if (_covered[j].end() == new_region.end()) { | |
| 506 changed_region = j; | |
| 507 // This is a case where the covered region is growing or shrinking | |
| 508 // at the start of the region. | |
| 509 assert(changed_region != -1, "Don't expect to add a covered region"); | |
| 510 assert(_covered[changed_region].byte_size() != new_region.byte_size(), | |
| 511 "The sizes should be different here"); | |
| 512 resize_covered_region_by_end(changed_region, new_region); | |
| 513 return; | |
| 514 } | |
| 515 } | |
| 516 // This should only be a new covered region (where no existing | |
| 517 // covered region matches at the start or the end). | |
| 518 assert(_cur_covered_regions < _max_covered_regions, | |
| 519 "An existing region should have been found"); | |
| 520 resize_covered_region_by_start(new_region); | |
| 521 } | |
| 522 | |
| 523 void CardTableExtension::resize_covered_region_by_start(MemRegion new_region) { | |
| 524 CardTableModRefBS::resize_covered_region(new_region); | |
| 525 debug_only(verify_guard();) | |
| 526 } | |
| 527 | |
| 528 void CardTableExtension::resize_covered_region_by_end(int changed_region, | |
| 529 MemRegion new_region) { | |
| 530 assert(SafepointSynchronize::is_at_safepoint(), | |
| 531 "Only expect an expansion at the low end at a GC"); | |
| 532 debug_only(verify_guard();) | |
| 533 #ifdef ASSERT | |
| 534 for (int k = 0; k < _cur_covered_regions; k++) { | |
| 535 if (_covered[k].end() == new_region.end()) { | |
| 536 assert(changed_region == k, "Changed region is incorrect"); | |
| 537 break; | |
| 538 } | |
| 539 } | |
| 540 #endif | |
| 541 | |
| 542 // Commit new or uncommit old pages, if necessary. | |
|
1612
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
543 if (resize_commit_uncommit(changed_region, new_region)) { |
|
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
544 // Set the new start of the committed region |
|
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
545 resize_update_committed_table(changed_region, new_region); |
|
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
546 } |
| 0 | 547 |
| 548 // Update card table entries | |
| 549 resize_update_card_table_entries(changed_region, new_region); | |
| 550 | |
| 551 // Update the covered region | |
| 552 resize_update_covered_table(changed_region, new_region); | |
| 553 | |
| 554 if (TraceCardTableModRefBS) { | |
| 555 int ind = changed_region; | |
| 556 gclog_or_tty->print_cr("CardTableModRefBS::resize_covered_region: "); | |
| 557 gclog_or_tty->print_cr(" " | |
| 558 " _covered[%d].start(): " INTPTR_FORMAT | |
| 559 " _covered[%d].last(): " INTPTR_FORMAT, | |
| 560 ind, _covered[ind].start(), | |
| 561 ind, _covered[ind].last()); | |
| 562 gclog_or_tty->print_cr(" " | |
| 563 " _committed[%d].start(): " INTPTR_FORMAT | |
| 564 " _committed[%d].last(): " INTPTR_FORMAT, | |
| 565 ind, _committed[ind].start(), | |
| 566 ind, _committed[ind].last()); | |
| 567 gclog_or_tty->print_cr(" " | |
| 568 " byte_for(start): " INTPTR_FORMAT | |
| 569 " byte_for(last): " INTPTR_FORMAT, | |
| 570 byte_for(_covered[ind].start()), | |
| 571 byte_for(_covered[ind].last())); | |
| 572 gclog_or_tty->print_cr(" " | |
| 573 " addr_for(start): " INTPTR_FORMAT | |
| 574 " addr_for(last): " INTPTR_FORMAT, | |
| 575 addr_for((jbyte*) _committed[ind].start()), | |
| 576 addr_for((jbyte*) _committed[ind].last())); | |
| 577 } | |
| 578 debug_only(verify_guard();) | |
| 579 } | |
| 580 | |
|
1612
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
581 bool CardTableExtension::resize_commit_uncommit(int changed_region, |
| 0 | 582 MemRegion new_region) { |
|
1612
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
583 bool result = false; |
| 0 | 584 // Commit new or uncommit old pages, if necessary. |
| 585 MemRegion cur_committed = _committed[changed_region]; | |
| 586 assert(_covered[changed_region].end() == new_region.end(), | |
| 587 "The ends of the regions are expected to match"); | |
| 588 // Extend the start of this _committed region to | |
| 589 // to cover the start of any previous _committed region. | |
| 590 // This forms overlapping regions, but never interior regions. | |
| 591 HeapWord* min_prev_start = lowest_prev_committed_start(changed_region); | |
| 592 if (min_prev_start < cur_committed.start()) { | |
| 593 // Only really need to set start of "cur_committed" to | |
| 594 // the new start (min_prev_start) but assertion checking code | |
| 595 // below use cur_committed.end() so make it correct. | |
| 596 MemRegion new_committed = | |
| 597 MemRegion(min_prev_start, cur_committed.end()); | |
| 598 cur_committed = new_committed; | |
| 599 } | |
| 600 #ifdef ASSERT | |
| 601 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); | |
| 602 assert(cur_committed.start() == | |
| 603 (HeapWord*) align_size_up((uintptr_t) cur_committed.start(), | |
| 604 os::vm_page_size()), | |
| 605 "Starts should have proper alignment"); | |
| 606 #endif | |
| 607 | |
| 608 jbyte* new_start = byte_for(new_region.start()); | |
| 609 // Round down because this is for the start address | |
| 610 HeapWord* new_start_aligned = | |
| 611 (HeapWord*)align_size_down((uintptr_t)new_start, os::vm_page_size()); | |
| 612 // The guard page is always committed and should not be committed over. | |
| 613 // This method is used in cases where the generation is growing toward | |
| 614 // lower addresses but the guard region is still at the end of the | |
| 615 // card table. That still makes sense when looking for writes | |
| 616 // off the end of the card table. | |
| 617 if (new_start_aligned < cur_committed.start()) { | |
| 618 // Expand the committed region | |
| 619 // | |
| 620 // Case A | |
| 621 // |+ guard +| | |
| 622 // |+ cur committed +++++++++| | |
| 623 // |+ new committed +++++++++++++++++| | |
| 624 // | |
| 625 // Case B | |
| 626 // |+ guard +| | |
| 627 // |+ cur committed +| | |
| 628 // |+ new committed +++++++| | |
| 629 // | |
| 630 // These are not expected because the calculation of the | |
| 631 // cur committed region and the new committed region | |
| 632 // share the same end for the covered region. | |
| 633 // Case C | |
| 634 // |+ guard +| | |
| 635 // |+ cur committed +| | |
| 636 // |+ new committed +++++++++++++++++| | |
| 637 // Case D | |
| 638 // |+ guard +| | |
| 639 // |+ cur committed +++++++++++| | |
| 640 // |+ new committed +++++++| | |
| 641 | |
| 642 HeapWord* new_end_for_commit = | |
| 643 MIN2(cur_committed.end(), _guard_region.start()); | |
|
263
12eea04c8b06
6672698: mangle_unused_area() should not remangle the entire heap at each collection.
jmasa
parents:
113
diff
changeset
|
644 if(new_start_aligned < new_end_for_commit) { |
|
12eea04c8b06
6672698: mangle_unused_area() should not remangle the entire heap at each collection.
jmasa
parents:
113
diff
changeset
|
645 MemRegion new_committed = |
|
12eea04c8b06
6672698: mangle_unused_area() should not remangle the entire heap at each collection.
jmasa
parents:
113
diff
changeset
|
646 MemRegion(new_start_aligned, new_end_for_commit); |
| 0 | 647 if (!os::commit_memory((char*)new_committed.start(), |
| 648 new_committed.byte_size())) { | |
| 649 vm_exit_out_of_memory(new_committed.byte_size(), | |
| 650 "card table expansion"); | |
| 651 } | |
| 652 } | |
|
1612
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
653 result = true; |
| 0 | 654 } else if (new_start_aligned > cur_committed.start()) { |
| 655 // Shrink the committed region | |
|
1612
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
656 #if 0 // uncommitting space is currently unsafe because of the interactions |
|
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
657 // of growing and shrinking regions. One region A can uncommit space |
|
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
658 // that it owns but which is being used by another region B (maybe). |
|
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
659 // Region B has not committed the space because it was already |
|
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
660 // committed by region A. |
| 0 | 661 MemRegion uncommit_region = committed_unique_to_self(changed_region, |
| 662 MemRegion(cur_committed.start(), new_start_aligned)); | |
| 663 if (!uncommit_region.is_empty()) { | |
| 664 if (!os::uncommit_memory((char*)uncommit_region.start(), | |
| 665 uncommit_region.byte_size())) { | |
|
1612
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
666 // If the uncommit fails, ignore it. Let the |
|
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
667 // committed table resizing go even though the committed |
|
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
668 // table will over state the committed space. |
| 0 | 669 } |
| 670 } | |
|
1612
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
671 #else |
|
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
672 assert(!result, "Should be false with current workaround"); |
|
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
673 #endif |
| 0 | 674 } |
| 675 assert(_committed[changed_region].end() == cur_committed.end(), | |
| 676 "end should not change"); | |
|
1612
fdde661c8e06
6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008
jmasa
parents:
1552
diff
changeset
|
677 return result; |
| 0 | 678 } |
| 679 | |
| 680 void CardTableExtension::resize_update_committed_table(int changed_region, | |
| 681 MemRegion new_region) { | |
| 682 | |
| 683 jbyte* new_start = byte_for(new_region.start()); | |
| 684 // Set the new start of the committed region | |
| 685 HeapWord* new_start_aligned = | |
| 686 (HeapWord*)align_size_down((uintptr_t)new_start, | |
| 687 os::vm_page_size()); | |
| 688 MemRegion new_committed = MemRegion(new_start_aligned, | |
| 689 _committed[changed_region].end()); | |
| 690 _committed[changed_region] = new_committed; | |
| 691 _committed[changed_region].set_start(new_start_aligned); | |
| 692 } | |
| 693 | |
| 694 void CardTableExtension::resize_update_card_table_entries(int changed_region, | |
| 695 MemRegion new_region) { | |
| 696 debug_only(verify_guard();) | |
| 697 MemRegion original_covered = _covered[changed_region]; | |
| 698 // Initialize the card entries. Only consider the | |
| 699 // region covered by the card table (_whole_heap) | |
| 700 jbyte* entry; | |
| 701 if (new_region.start() < _whole_heap.start()) { | |
| 702 entry = byte_for(_whole_heap.start()); | |
| 703 } else { | |
| 704 entry = byte_for(new_region.start()); | |
| 705 } | |
| 706 jbyte* end = byte_for(original_covered.start()); | |
| 707 // If _whole_heap starts at the original covered regions start, | |
| 708 // this loop will not execute. | |
| 709 while (entry < end) { *entry++ = clean_card; } | |
| 710 } | |
| 711 | |
| 712 void CardTableExtension::resize_update_covered_table(int changed_region, | |
| 713 MemRegion new_region) { | |
| 714 // Update the covered region | |
| 715 _covered[changed_region].set_start(new_region.start()); | |
| 716 _covered[changed_region].set_word_size(new_region.word_size()); | |
| 717 | |
| 718 // reorder regions. There should only be at most 1 out | |
| 719 // of order. | |
| 720 for (int i = _cur_covered_regions-1 ; i > 0; i--) { | |
| 721 if (_covered[i].start() < _covered[i-1].start()) { | |
| 722 MemRegion covered_mr = _covered[i-1]; | |
| 723 _covered[i-1] = _covered[i]; | |
| 724 _covered[i] = covered_mr; | |
| 725 MemRegion committed_mr = _committed[i-1]; | |
| 726 _committed[i-1] = _committed[i]; | |
| 727 _committed[i] = committed_mr; | |
| 728 break; | |
| 729 } | |
| 730 } | |
| 731 #ifdef ASSERT | |
| 732 for (int m = 0; m < _cur_covered_regions-1; m++) { | |
| 733 assert(_covered[m].start() <= _covered[m+1].start(), | |
| 734 "Covered regions out of order"); | |
| 735 assert(_committed[m].start() <= _committed[m+1].start(), | |
| 736 "Committed regions out of order"); | |
| 737 } | |
| 738 #endif | |
| 739 } | |
| 740 | |
| 741 // Returns the start of any committed region that is lower than | |
| 742 // the target committed region (index ind) and that intersects the | |
| 743 // target region. If none, return start of target region. | |
| 744 // | |
| 745 // ------------- | |
| 746 // | | | |
| 747 // ------------- | |
| 748 // ------------ | |
| 749 // | target | | |
| 750 // ------------ | |
| 751 // ------------- | |
| 752 // | | | |
| 753 // ------------- | |
| 754 // ^ returns this | |
| 755 // | |
| 756 // ------------- | |
| 757 // | | | |
| 758 // ------------- | |
| 759 // ------------ | |
| 760 // | target | | |
| 761 // ------------ | |
| 762 // ------------- | |
| 763 // | | | |
| 764 // ------------- | |
| 765 // ^ returns this | |
| 766 | |
| 767 HeapWord* CardTableExtension::lowest_prev_committed_start(int ind) const { | |
| 768 assert(_cur_covered_regions >= 0, "Expecting at least on region"); | |
| 769 HeapWord* min_start = _committed[ind].start(); | |
| 770 for (int j = 0; j < ind; j++) { | |
| 771 HeapWord* this_start = _committed[j].start(); | |
| 772 if ((this_start < min_start) && | |
| 773 !(_committed[j].intersection(_committed[ind])).is_empty()) { | |
| 774 min_start = this_start; | |
| 775 } | |
| 776 } | |
| 777 return min_start; | |
| 778 } |