1 /*
2 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "memory/compactingPermGenGen.hpp"
29 #include "memory/filemap.hpp"
30 #include "memory/genOopClosures.inline.hpp"
31 #include "memory/generation.inline.hpp"
32 #include "memory/generationSpec.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "runtime/java.hpp"
35 #ifndef SERIALGC
36 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
37 #endif
38
39
40 // An ObjectClosure helper: Recursively adjust all pointers in an object
41 // and all objects by referenced it. Clear marks on objects in order to
42 // prevent visiting any object twice. This helper is used when the
43 // RedefineClasses() API has been called.
44
45 class AdjustSharedObjectClosure : public ObjectClosure {
46 public:
47 void do_object(oop obj) {
48 if (obj->is_shared_readwrite()) {
49 if (obj->mark()->is_marked()) {
50 obj->init_mark(); // Don't revisit this object.
51 obj->adjust_pointers(); // Adjust this object's references.
52 }
53 }
54 }
55 };
56
57
58 // An OopClosure helper: Recursively adjust all pointers in an object
59 // and all objects by referenced it. Clear marks on objects in order
60 // to prevent visiting any object twice.
61
62 class RecursiveAdjustSharedObjectClosure : public OopClosure {
63 protected:
64 template <class T> inline void do_oop_work(T* p) {
65 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
66 if (obj->is_shared_readwrite()) {
67 if (obj->mark()->is_marked()) {
68 obj->init_mark(); // Don't revisit this object.
69 obj->oop_iterate(this); // Recurse - adjust objects referenced.
70 obj->adjust_pointers(); // Adjust this object's references.
71
72 // Special case: if a class has a read-only constant pool,
73 // then the read-write objects referenced by the pool must
74 // have their marks reset.
75
76 if (obj->klass() == Universe::instanceKlassKlassObj()) {
77 instanceKlass* ik = instanceKlass::cast((klassOop)obj);
78 constantPoolOop cp = ik->constants();
79 if (cp->is_shared_readonly()) {
80 cp->oop_iterate(this);
81 }
82 }
83 }
84 }
85 }
86 public:
87 virtual void do_oop(oop* p) { RecursiveAdjustSharedObjectClosure::do_oop_work(p); }
88 virtual void do_oop(narrowOop* p) { RecursiveAdjustSharedObjectClosure::do_oop_work(p); }
89 };
90
91
92 // We need to go through all placeholders in the system dictionary and
93 // try to resolve them into shared classes. Other threads might be in
94 // the process of loading a shared class and have strong roots on
95 // their stack to the class without having added the class to the
96 // dictionary yet. This means the class will be marked during phase 1
97 // but will not be unmarked during the application of the
98 // RecursiveAdjustSharedObjectClosure to the SystemDictionary. Note
99 // that we must not call find_shared_class with non-read-only symbols
100 // as doing so can cause hash codes to be computed, destroying
101 // forwarding pointers.
102 class TraversePlaceholdersClosure : public OopClosure {
103 protected:
104 template <class T> inline void do_oop_work(T* p) {
105 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
106 if (obj->klass() == Universe::symbolKlassObj() &&
107 obj->is_shared_readonly()) {
108 symbolHandle sym((symbolOop) obj);
109 oop k = SystemDictionary::find_shared_class(sym);
110 if (k != NULL) {
111 RecursiveAdjustSharedObjectClosure clo;
112 clo.do_oop(&k);
113 }
114 }
115 }
116 public:
117 virtual void do_oop(oop* p) { TraversePlaceholdersClosure::do_oop_work(p); }
118 virtual void do_oop(narrowOop* p) { TraversePlaceholdersClosure::do_oop_work(p); }
119
120 };
121
122
123 void CompactingPermGenGen::initialize_performance_counters() {
124
125 const char* gen_name = "perm";
126
127 // Generation Counters - generation 2, 1 subspace
128 _gen_counters = new GenerationCounters(gen_name, 2, 1, &_virtual_space);
129
130 _space_counters = new CSpaceCounters(gen_name, 0,
131 _virtual_space.reserved_size(),
132 _the_space, _gen_counters);
133 }
134
135 void CompactingPermGenGen::update_counters() {
136 if (UsePerfData) {
137 _space_counters->update_all();
138 _gen_counters->update_all();
139 }
140 }
141
142
143 CompactingPermGenGen::CompactingPermGenGen(ReservedSpace rs,
144 ReservedSpace shared_rs,
145 size_t initial_byte_size,
146 int level, GenRemSet* remset,
147 ContiguousSpace* space,
148 PermanentGenerationSpec* spec_) :
149 OneContigSpaceCardGeneration(rs, initial_byte_size, MinPermHeapExpansion,
150 level, remset, space) {
151
152 set_spec(spec_);
153 if (!UseSharedSpaces && !DumpSharedSpaces) {
154 spec()->disable_sharing();
155 }
156
157 // Break virtual space into address ranges for all spaces.
158
159 if (spec()->enable_shared_spaces()) {
160 shared_end = (HeapWord*)(shared_rs.base() + shared_rs.size());
161 misccode_end = shared_end;
162 misccode_bottom = misccode_end - heap_word_size(spec()->misc_code_size());
163 miscdata_end = misccode_bottom;
164 miscdata_bottom = miscdata_end - heap_word_size(spec()->misc_data_size());
165 readwrite_end = miscdata_bottom;
166 readwrite_bottom =
167 readwrite_end - heap_word_size(spec()->read_write_size());
168 readonly_end = readwrite_bottom;
169 readonly_bottom =
170 readonly_end - heap_word_size(spec()->read_only_size());
171 shared_bottom = readonly_bottom;
172 unshared_end = shared_bottom;
173 assert((char*)shared_bottom == shared_rs.base(), "shared space mismatch");
174 } else {
175 shared_end = (HeapWord*)(rs.base() + rs.size());
176 misccode_end = shared_end;
177 misccode_bottom = shared_end;
178 miscdata_end = shared_end;
179 miscdata_bottom = shared_end;
180 readwrite_end = shared_end;
181 readwrite_bottom = shared_end;
182 readonly_end = shared_end;
183 readonly_bottom = shared_end;
184 shared_bottom = shared_end;
185 unshared_end = shared_bottom;
186 }
187 unshared_bottom = (HeapWord*) rs.base();
188
189 // Verify shared and unshared spaces adjacent.
190 assert((char*)shared_bottom == rs.base()+rs.size(), "shared space mismatch");
191 assert(unshared_end > unshared_bottom, "shared space mismatch");
192
193 // Split reserved memory into pieces.
194
195 ReservedSpace ro_rs = shared_rs.first_part(spec()->read_only_size(),
196 UseSharedSpaces);
197 ReservedSpace tmp_rs1 = shared_rs.last_part(spec()->read_only_size());
198 ReservedSpace rw_rs = tmp_rs1.first_part(spec()->read_write_size(),
199 UseSharedSpaces);
200 ReservedSpace tmp_rs2 = tmp_rs1.last_part(spec()->read_write_size());
201 ReservedSpace md_rs = tmp_rs2.first_part(spec()->misc_data_size(),
202 UseSharedSpaces);
203 ReservedSpace mc_rs = tmp_rs2.last_part(spec()->misc_data_size());
204
205 _shared_space_size = spec()->read_only_size()
206 + spec()->read_write_size()
207 + spec()->misc_data_size()
208 + spec()->misc_code_size();
209
210 // Allocate the unshared (default) space.
211 _the_space = new ContigPermSpace(_bts,
212 MemRegion(unshared_bottom, heap_word_size(initial_byte_size)));
213 if (_the_space == NULL)
214 vm_exit_during_initialization("Could not allocate an unshared"
215 " CompactingPermGen Space");
216
217 // Allocate shared spaces
218 if (spec()->enable_shared_spaces()) {
219
220 // If mapping a shared file, the space is not committed, don't
221 // mangle.
222 NOT_PRODUCT(bool old_ZapUnusedHeapArea = ZapUnusedHeapArea;)
223 NOT_PRODUCT(if (UseSharedSpaces) ZapUnusedHeapArea = false;)
224
225 // Commit the memory behind the shared spaces if dumping (not
226 // mapping).
227 if (DumpSharedSpaces) {
228 _ro_vs.initialize(ro_rs, spec()->read_only_size());
229 _rw_vs.initialize(rw_rs, spec()->read_write_size());
230 _md_vs.initialize(md_rs, spec()->misc_data_size());
231 _mc_vs.initialize(mc_rs, spec()->misc_code_size());
232 }
233
234 // Allocate the shared spaces.
235 _ro_bts = new BlockOffsetSharedArray(
236 MemRegion(readonly_bottom,
237 heap_word_size(spec()->read_only_size())),
238 heap_word_size(spec()->read_only_size()));
239 _ro_space = new OffsetTableContigSpace(_ro_bts,
240 MemRegion(readonly_bottom, readonly_end));
241 _rw_bts = new BlockOffsetSharedArray(
242 MemRegion(readwrite_bottom,
243 heap_word_size(spec()->read_write_size())),
244 heap_word_size(spec()->read_write_size()));
245 _rw_space = new OffsetTableContigSpace(_rw_bts,
246 MemRegion(readwrite_bottom, readwrite_end));
247
248 // Restore mangling flag.
249 NOT_PRODUCT(ZapUnusedHeapArea = old_ZapUnusedHeapArea;)
250
251 if (_ro_space == NULL || _rw_space == NULL)
252 vm_exit_during_initialization("Could not allocate a shared space");
253
254 // Cover both shared spaces entirely with cards.
255 _rs->resize_covered_region(MemRegion(readonly_bottom, readwrite_end));
256
257 if (UseSharedSpaces) {
258
259 // Map in the regions in the shared file.
260 FileMapInfo* mapinfo = FileMapInfo::current_info();
261 size_t image_alignment = mapinfo->alignment();
262 CollectedHeap* ch = Universe::heap();
263 if ((!mapinfo->map_space(ro, ro_rs, _ro_space)) ||
264 (!mapinfo->map_space(rw, rw_rs, _rw_space)) ||
265 (!mapinfo->map_space(md, md_rs, NULL)) ||
266 (!mapinfo->map_space(mc, mc_rs, NULL)) ||
267 // check the alignment constraints
268 (ch == NULL || ch->kind() != CollectedHeap::GenCollectedHeap ||
269 image_alignment !=
270 ((GenCollectedHeap*)ch)->gen_policy()->max_alignment())) {
271 // Base addresses didn't match; skip sharing, but continue
272 shared_rs.release();
273 spec()->disable_sharing();
274 // If -Xshare:on is specified, print out the error message and exit VM,
275 // otherwise, set UseSharedSpaces to false and continue.
276 if (RequireSharedSpaces) {
277 vm_exit_during_initialization("Unable to use shared archive.", NULL);
278 } else {
279 FLAG_SET_DEFAULT(UseSharedSpaces, false);
280 }
281
282 // Note: freeing the block offset array objects does not
283 // currently free up the underlying storage.
284 delete _ro_bts;
285 _ro_bts = NULL;
286 delete _ro_space;
287 _ro_space = NULL;
288 delete _rw_bts;
289 _rw_bts = NULL;
290 delete _rw_space;
291 _rw_space = NULL;
292 shared_end = (HeapWord*)(rs.base() + rs.size());
293 _rs->resize_covered_region(MemRegion(shared_bottom, shared_bottom));
294 }
295 }
296
297 // Reserved region includes shared spaces for oop.is_in_reserved().
298 _reserved.set_end(shared_end);
299
300 } else {
301 _ro_space = NULL;
302 _rw_space = NULL;
303 }
304 }
305
306
307 // Do a complete scan of the shared read write space to catch all
308 // objects which contain references to any younger generation. Forward
309 // the pointers. Avoid space_iterate, as actually visiting all the
310 // objects in the space will page in more objects than we need.
311 // Instead, use the system dictionary as strong roots into the read
312 // write space.
313 //
314 // If a RedefineClasses() call has been made, then we have to iterate
315 // over the entire shared read-write space in order to find all the
316 // objects that need to be forwarded. For example, it is possible for
317 // an nmethod to be found and marked in GC phase-1 only for the nmethod
318 // to be freed by the time we reach GC phase-3. The underlying method
319 // is still marked, but we can't (easily) find it in GC phase-3 so we
320 // blow up in GC phase-4. With RedefineClasses() we want replaced code
321 // (EMCP or obsolete) to go away (i.e., be collectible) once it is no
322 // longer being executed by any thread so we keep minimal attachments
323 // to the replaced code. However, we can't guarantee when those EMCP
324 // or obsolete methods will be collected so they may still be out there
325 // even after we've severed our minimal attachments.
326
327 void CompactingPermGenGen::pre_adjust_pointers() {
328 if (spec()->enable_shared_spaces()) {
329 if (JvmtiExport::has_redefined_a_class()) {
330 // RedefineClasses() requires a brute force approach
331 AdjustSharedObjectClosure blk;
332 rw_space()->object_iterate(&blk);
333 } else {
334 RecursiveAdjustSharedObjectClosure blk;
335 Universe::oops_do(&blk);
336 StringTable::oops_do(&blk);
337 SystemDictionary::always_strong_classes_do(&blk);
338 TraversePlaceholdersClosure tpc;
339 SystemDictionary::placeholders_do(&tpc);
340 }
341 }
342 }
343
344
345 #ifdef ASSERT
346 class VerifyMarksClearedClosure : public ObjectClosure {
347 public:
348 void do_object(oop obj) {
349 assert(SharedSkipVerify || !obj->mark()->is_marked(),
350 "Shared oop still marked?");
351 }
352 };
353 #endif
354
355
356 void CompactingPermGenGen::post_compact() {
357 #ifdef ASSERT
358 if (!SharedSkipVerify && spec()->enable_shared_spaces()) {
359 VerifyMarksClearedClosure blk;
360 rw_space()->object_iterate(&blk);
361 }
362 #endif
363 }
364
365
366 // Do not use in time-critical operations due to the possibility of paging
367 // in otherwise untouched or previously unread portions of the perm gen,
368 // for instance, the shared spaces. NOTE: Because CompactingPermGenGen
369 // derives from OneContigSpaceCardGeneration which is supposed to have a
370 // single space, and does not override its object_iterate() method,
371 // object iteration via that interface does not look at the objects in
372 // the shared spaces when using CDS. This should be fixed; see CR 6897798.
373 void CompactingPermGenGen::space_iterate(SpaceClosure* blk, bool usedOnly) {
374 OneContigSpaceCardGeneration::space_iterate(blk, usedOnly);
375 if (spec()->enable_shared_spaces()) {
376 // Making the rw_space walkable will page in the entire space, and
377 // is to be avoided in the case of time-critical operations.
378 // However, this is required for Verify and heap dump operations.
379 blk->do_space(ro_space());
380 blk->do_space(rw_space());
381 }
382 }
383
384
385 void CompactingPermGenGen::print_on(outputStream* st) const {
386 OneContigSpaceCardGeneration::print_on(st);
387 if (spec()->enable_shared_spaces()) {
388 st->print(" ro");
389 ro_space()->print_on(st);
390 st->print(" rw");
391 rw_space()->print_on(st);
392 } else {
393 st->print_cr("No shared spaces configured.");
394 }
395 }
396
397
398 // References from the perm gen to the younger generation objects may
399 // occur in static fields in Java classes or in constant pool references
400 // to String objects.
401
402 void CompactingPermGenGen::younger_refs_iterate(OopsInGenClosure* blk) {
403 OneContigSpaceCardGeneration::younger_refs_iterate(blk);
404 if (spec()->enable_shared_spaces()) {
405 blk->set_generation(this);
406 // ro_space has no younger gen refs.
407 _rs->younger_refs_in_space_iterate(rw_space(), blk);
408 blk->reset_generation();
409 }
410 }
411
412
413 // Shared spaces are addressed in pre_adjust_pointers.
414 void CompactingPermGenGen::adjust_pointers() {
415 the_space()->adjust_pointers();
416 }
417
418
419 void CompactingPermGenGen::compact() {
420 the_space()->compact();
421 }
422
423
424 size_t CompactingPermGenGen::contiguous_available() const {
425 // Don't include shared spaces.
426 return OneContigSpaceCardGeneration::contiguous_available()
427 - _shared_space_size;
428 }
429
430 size_t CompactingPermGenGen::max_capacity() const {
431 // Don't include shared spaces.
432 assert(UseSharedSpaces || (_shared_space_size == 0),
433 "If not used, the size of shared spaces should be 0");
434 return OneContigSpaceCardGeneration::max_capacity()
435 - _shared_space_size;
436 }
437
438
439 // No young generation references, clear this generation's main space's
440 // card table entries. Do NOT clear the card table entries for the
441 // read-only space (always clear) or the read-write space (valuable
442 // information).
443
444 void CompactingPermGenGen::clear_remembered_set() {
445 _rs->clear(MemRegion(the_space()->bottom(), the_space()->end()));
446 }
447
448
449 // Objects in this generation's main space may have moved, invalidate
450 // that space's cards. Do NOT invalidate the card table entries for the
451 // read-only or read-write spaces, as those objects never move.
452
453 void CompactingPermGenGen::invalidate_remembered_set() {
454 _rs->invalidate(used_region());
455 }
456
457
458 void CompactingPermGenGen::verify(bool allow_dirty) {
459 the_space()->verify(allow_dirty);
460 if (!SharedSkipVerify && spec()->enable_shared_spaces()) {
461 ro_space()->verify(allow_dirty);
462 rw_space()->verify(allow_dirty);
463 }
464 }
465
466
467 HeapWord* CompactingPermGenGen::unshared_bottom;
468 HeapWord* CompactingPermGenGen::unshared_end;
469 HeapWord* CompactingPermGenGen::shared_bottom;
470 HeapWord* CompactingPermGenGen::shared_end;
471 HeapWord* CompactingPermGenGen::readonly_bottom;
472 HeapWord* CompactingPermGenGen::readonly_end;
473 HeapWord* CompactingPermGenGen::readwrite_bottom;
474 HeapWord* CompactingPermGenGen::readwrite_end;
475 HeapWord* CompactingPermGenGen::miscdata_bottom;
476 HeapWord* CompactingPermGenGen::miscdata_end;
477 HeapWord* CompactingPermGenGen::misccode_bottom;
478 HeapWord* CompactingPermGenGen::misccode_end;
479
480 // JVM/TI RedefineClasses() support:
481 bool CompactingPermGenGen::remap_shared_readonly_as_readwrite() {
482 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
483
484 if (UseSharedSpaces) {
485 // remap the shared readonly space to shared readwrite, private
486 FileMapInfo* mapinfo = FileMapInfo::current_info();
487 if (!mapinfo->remap_shared_readonly_as_readwrite()) {
488 return false;
489 }
490 }
491 return true;
492 }
493
494 void** CompactingPermGenGen::_vtbl_list;