1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/memory/genMarkSweep.cpp Sat Dec 01 00:00:00 2007 +0000
1.3 @@ -0,0 +1,392 @@
1.4 +/*
1.5 + * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
1.23 + * CA 95054 USA or visit www.sun.com if you need additional information or
1.24 + * have any questions.
1.25 + *
1.26 + */
1.27 +
1.28 +#include "incls/_precompiled.incl"
1.29 +#include "incls/_genMarkSweep.cpp.incl"
1.30 +
1.31 +void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp,
1.32 + bool clear_all_softrefs) {
1.33 + assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1.34 +
1.35 + // hook up weak ref data so it can be used during Mark-Sweep
1.36 + assert(ref_processor() == NULL, "no stomping");
1.37 + _ref_processor = rp;
1.38 + assert(rp != NULL, "should be non-NULL");
1.39 +
1.40 + TraceTime t1("Full GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
1.41 +
1.42 + // When collecting the permanent generation methodOops may be moving,
1.43 + // so we either have to flush all bcp data or convert it into bci.
1.44 + CodeCache::gc_prologue();
1.45 + Threads::gc_prologue();
1.46 +
1.47 + // Increment the invocation count for the permanent generation, since it is
1.48 + // implicitly collected whenever we do a full mark sweep collection.
1.49 + GenCollectedHeap* gch = GenCollectedHeap::heap();
1.50 + gch->perm_gen()->stat_record()->invocations++;
1.51 +
1.52 + // Capture heap size before collection for printing.
1.53 + size_t gch_prev_used = gch->used();
1.54 +
1.55 + // Some of the card table updates below assume that the perm gen is
1.56 + // also being collected.
1.57 + assert(level == gch->n_gens() - 1,
1.58 + "All generations are being collected, ergo perm gen too.");
1.59 +
1.60 + // Capture used regions for each generation that will be
1.61 + // subject to collection, so that card table adjustments can
1.62 + // be made intelligently (see clear / invalidate further below).
1.63 + gch->save_used_regions(level, true /* perm */);
1.64 +
1.65 + allocate_stacks();
1.66 +
1.67 + mark_sweep_phase1(level, clear_all_softrefs);
1.68 +
1.69 + mark_sweep_phase2();
1.70 +
1.71 + // Don't add any more derived pointers during phase3
1.72 + COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
1.73 + COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
1.74 +
1.75 + mark_sweep_phase3(level);
1.76 +
1.77 + VALIDATE_MARK_SWEEP_ONLY(
1.78 + if (ValidateMarkSweep) {
1.79 + guarantee(_root_refs_stack->length() == 0,
1.80 + "should be empty by now");
1.81 + }
1.82 + )
1.83 +
1.84 + mark_sweep_phase4();
1.85 +
1.86 + VALIDATE_MARK_SWEEP_ONLY(
1.87 + if (ValidateMarkSweep) {
1.88 + guarantee(_live_oops->length() == _live_oops_moved_to->length(),
1.89 + "should be the same size");
1.90 + }
1.91 + )
1.92 +
1.93 + restore_marks();
1.94 +
1.95 + // Set saved marks for allocation profiler (and other things? -- dld)
1.96 + // (Should this be in general part?)
1.97 + gch->save_marks();
1.98 +
1.99 + deallocate_stacks();
1.100 +
1.101 + // If compaction completely evacuated all generations younger than this
1.102 + // one, then we can clear the card table. Otherwise, we must invalidate
1.103 + // it (consider all cards dirty). In the future, we might consider doing
1.104 + // compaction within generations only, and doing card-table sliding.
1.105 + bool all_empty = true;
1.106 + for (int i = 0; all_empty && i < level; i++) {
1.107 + Generation* g = gch->get_gen(i);
1.108 + all_empty = all_empty && gch->get_gen(i)->used() == 0;
1.109 + }
1.110 + GenRemSet* rs = gch->rem_set();
1.111 + // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
1.112 + if (all_empty) {
1.113 + // We've evacuated all generations below us.
1.114 + Generation* g = gch->get_gen(level);
1.115 + rs->clear_into_younger(g, true /* perm */);
1.116 + } else {
1.117 + // Invalidate the cards corresponding to the currently used
1.118 + // region and clear those corresponding to the evacuated region
1.119 + // of all generations just collected (i.e. level and younger).
1.120 + rs->invalidate_or_clear(gch->get_gen(level),
1.121 + true /* younger */,
1.122 + true /* perm */);
1.123 + }
1.124 +
1.125 + Threads::gc_epilogue();
1.126 + CodeCache::gc_epilogue();
1.127 +
1.128 + if (PrintGC && !PrintGCDetails) {
1.129 + gch->print_heap_change(gch_prev_used);
1.130 + }
1.131 +
1.132 + // refs processing: clean slate
1.133 + _ref_processor = NULL;
1.134 +
1.135 + // Update heap occupancy information which is used as
1.136 + // input to soft ref clearing policy at the next gc.
1.137 + Universe::update_heap_info_at_gc();
1.138 +
1.139 + // Update time of last gc for all generations we collected
1.140 + // (which curently is all the generations in the heap).
1.141 + gch->update_time_of_last_gc(os::javaTimeMillis());
1.142 +}
1.143 +
1.144 +void GenMarkSweep::allocate_stacks() {
1.145 + GenCollectedHeap* gch = GenCollectedHeap::heap();
1.146 + // Scratch request on behalf of oldest generation; will do no
1.147 + // allocation.
1.148 + ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
1.149 +
1.150 + // $$$ To cut a corner, we'll only use the first scratch block, and then
1.151 + // revert to malloc.
1.152 + if (scratch != NULL) {
1.153 + _preserved_count_max =
1.154 + scratch->num_words * HeapWordSize / sizeof(PreservedMark);
1.155 + } else {
1.156 + _preserved_count_max = 0;
1.157 + }
1.158 +
1.159 + _preserved_marks = (PreservedMark*)scratch;
1.160 + _preserved_count = 0;
1.161 + _preserved_mark_stack = NULL;
1.162 + _preserved_oop_stack = NULL;
1.163 +
1.164 + _marking_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
1.165 +
1.166 + int size = SystemDictionary::number_of_classes() * 2;
1.167 + _revisit_klass_stack = new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true);
1.168 +
1.169 +#ifdef VALIDATE_MARK_SWEEP
1.170 + if (ValidateMarkSweep) {
1.171 + _root_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<oop*>(100, true);
1.172 + _other_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<oop*>(100, true);
1.173 + _adjusted_pointers = new (ResourceObj::C_HEAP) GrowableArray<oop*>(100, true);
1.174 + _live_oops = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
1.175 + _live_oops_moved_to = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
1.176 + _live_oops_size = new (ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
1.177 + }
1.178 + if (RecordMarkSweepCompaction) {
1.179 + if (_cur_gc_live_oops == NULL) {
1.180 + _cur_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
1.181 + _cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
1.182 + _cur_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
1.183 + _last_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
1.184 + _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
1.185 + _last_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
1.186 + } else {
1.187 + _cur_gc_live_oops->clear();
1.188 + _cur_gc_live_oops_moved_to->clear();
1.189 + _cur_gc_live_oops_size->clear();
1.190 + }
1.191 + }
1.192 +#endif
1.193 +}
1.194 +
1.195 +
1.196 +void GenMarkSweep::deallocate_stacks() {
1.197 + if (_preserved_oop_stack) {
1.198 + delete _preserved_mark_stack;
1.199 + _preserved_mark_stack = NULL;
1.200 + delete _preserved_oop_stack;
1.201 + _preserved_oop_stack = NULL;
1.202 + }
1.203 +
1.204 + delete _marking_stack;
1.205 + delete _revisit_klass_stack;
1.206 +
1.207 +#ifdef VALIDATE_MARK_SWEEP
1.208 + if (ValidateMarkSweep) {
1.209 + delete _root_refs_stack;
1.210 + delete _other_refs_stack;
1.211 + delete _adjusted_pointers;
1.212 + delete _live_oops;
1.213 + delete _live_oops_size;
1.214 + delete _live_oops_moved_to;
1.215 + _live_oops_index = 0;
1.216 + _live_oops_index_at_perm = 0;
1.217 + }
1.218 +#endif
1.219 +}
1.220 +
1.221 +void GenMarkSweep::mark_sweep_phase1(int level,
1.222 + bool clear_all_softrefs) {
1.223 + // Recursively traverse all live objects and mark them
1.224 + EventMark m("1 mark object");
1.225 + TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
1.226 + trace(" 1");
1.227 +
1.228 + VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
1.229 +
1.230 + GenCollectedHeap* gch = GenCollectedHeap::heap();
1.231 +
1.232 + // Because follow_root_closure is created statically, cannot
1.233 + // use OopsInGenClosure constructor which takes a generation,
1.234 + // as the Universe has not been created when the static constructors
1.235 + // are run.
1.236 + follow_root_closure.set_orig_generation(gch->get_gen(level));
1.237 +
1.238 + gch->gen_process_strong_roots(level,
1.239 + false, // Younger gens are not roots.
1.240 + true, // Collecting permanent generation.
1.241 + SharedHeap::SO_SystemClasses,
1.242 + &follow_root_closure, &follow_root_closure);
1.243 +
1.244 + // Process reference objects found during marking
1.245 + {
1.246 + ReferencePolicy *soft_ref_policy;
1.247 + if (clear_all_softrefs) {
1.248 + soft_ref_policy = new AlwaysClearPolicy();
1.249 + } else {
1.250 +#ifdef COMPILER2
1.251 + soft_ref_policy = new LRUMaxHeapPolicy();
1.252 +#else
1.253 + soft_ref_policy = new LRUCurrentHeapPolicy();
1.254 +#endif // COMPILER2
1.255 + }
1.256 + assert(soft_ref_policy != NULL,"No soft reference policy");
1.257 + ref_processor()->process_discovered_references(
1.258 + soft_ref_policy, &is_alive, &keep_alive,
1.259 + &follow_stack_closure, NULL);
1.260 + }
1.261 +
1.262 + // Follow system dictionary roots and unload classes
1.263 + bool purged_class = SystemDictionary::do_unloading(&is_alive);
1.264 +
1.265 + // Follow code cache roots
1.266 + CodeCache::do_unloading(&is_alive, &keep_alive, purged_class);
1.267 + follow_stack(); // Flush marking stack
1.268 +
1.269 + // Update subklass/sibling/implementor links of live klasses
1.270 + follow_weak_klass_links();
1.271 + assert(_marking_stack->is_empty(), "just drained");
1.272 +
1.273 + // Visit symbol and interned string tables and delete unmarked oops
1.274 + SymbolTable::unlink(&is_alive);
1.275 + StringTable::unlink(&is_alive);
1.276 +
1.277 + assert(_marking_stack->is_empty(), "stack should be empty by now");
1.278 +}
1.279 +
1.280 +
1.281 +void GenMarkSweep::mark_sweep_phase2() {
1.282 + // Now all live objects are marked, compute the new object addresses.
1.283 +
1.284 + // It is imperative that we traverse perm_gen LAST. If dead space is
1.285 + // allowed a range of dead object may get overwritten by a dead int
1.286 + // array. If perm_gen is not traversed last a klassOop may get
1.287 + // overwritten. This is fine since it is dead, but if the class has dead
1.288 + // instances we have to skip them, and in order to find their size we
1.289 + // need the klassOop!
1.290 + //
1.291 + // It is not required that we traverse spaces in the same order in
1.292 + // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
1.293 + // tracking expects us to do so. See comment under phase4.
1.294 +
1.295 + GenCollectedHeap* gch = GenCollectedHeap::heap();
1.296 + Generation* pg = gch->perm_gen();
1.297 +
1.298 + EventMark m("2 compute new addresses");
1.299 + TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
1.300 + trace("2");
1.301 +
1.302 + VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
1.303 +
1.304 + gch->prepare_for_compaction();
1.305 +
1.306 + VALIDATE_MARK_SWEEP_ONLY(_live_oops_index_at_perm = _live_oops_index);
1.307 + CompactPoint perm_cp(pg, NULL, NULL);
1.308 + pg->prepare_for_compaction(&perm_cp);
1.309 +}
1.310 +
1.311 +class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
1.312 +public:
1.313 + void do_generation(Generation* gen) {
1.314 + gen->adjust_pointers();
1.315 + }
1.316 +};
1.317 +
1.318 +void GenMarkSweep::mark_sweep_phase3(int level) {
1.319 + GenCollectedHeap* gch = GenCollectedHeap::heap();
1.320 + Generation* pg = gch->perm_gen();
1.321 +
1.322 + // Adjust the pointers to reflect the new locations
1.323 + EventMark m("3 adjust pointers");
1.324 + TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
1.325 + trace("3");
1.326 +
1.327 + VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
1.328 +
1.329 + // Needs to be done before the system dictionary is adjusted.
1.330 + pg->pre_adjust_pointers();
1.331 +
1.332 + // Because the two closures below are created statically, cannot
1.333 + // use OopsInGenClosure constructor which takes a generation,
1.334 + // as the Universe has not been created when the static constructors
1.335 + // are run.
1.336 + adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));
1.337 + adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
1.338 +
1.339 + gch->gen_process_strong_roots(level,
1.340 + false, // Younger gens are not roots.
1.341 + true, // Collecting permanent generation.
1.342 + SharedHeap::SO_AllClasses,
1.343 + &adjust_root_pointer_closure,
1.344 + &adjust_root_pointer_closure);
1.345 +
1.346 + // Now adjust pointers in remaining weak roots. (All of which should
1.347 + // have been cleared if they pointed to non-surviving objects.)
1.348 + gch->gen_process_weak_roots(&adjust_root_pointer_closure,
1.349 + &adjust_pointer_closure);
1.350 +
1.351 + adjust_marks();
1.352 + GenAdjustPointersClosure blk;
1.353 + gch->generation_iterate(&blk, true);
1.354 + pg->adjust_pointers();
1.355 +}
1.356 +
1.357 +class GenCompactClosure: public GenCollectedHeap::GenClosure {
1.358 +public:
1.359 + void do_generation(Generation* gen) {
1.360 + gen->compact();
1.361 + }
1.362 +};
1.363 +
1.364 +void GenMarkSweep::mark_sweep_phase4() {
1.365 + // All pointers are now adjusted, move objects accordingly
1.366 +
1.367 + // It is imperative that we traverse perm_gen first in phase4. All
1.368 + // classes must be allocated earlier than their instances, and traversing
1.369 + // perm_gen first makes sure that all klassOops have moved to their new
1.370 + // location before any instance does a dispatch through it's klass!
1.371 +
1.372 + // The ValidateMarkSweep live oops tracking expects us to traverse spaces
1.373 + // in the same order in phase2, phase3 and phase4. We don't quite do that
1.374 + // here (perm_gen first rather than last), so we tell the validate code
1.375 + // to use a higher index (saved from phase2) when verifying perm_gen.
1.376 + GenCollectedHeap* gch = GenCollectedHeap::heap();
1.377 + Generation* pg = gch->perm_gen();
1.378 +
1.379 + EventMark m("4 compact heap");
1.380 + TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
1.381 + trace("4");
1.382 +
1.383 + VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(true));
1.384 +
1.385 + pg->compact();
1.386 +
1.387 + VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
1.388 +
1.389 + GenCompactClosure blk;
1.390 + gch->generation_iterate(&blk, true);
1.391 +
1.392 + VALIDATE_MARK_SWEEP_ONLY(compaction_complete());
1.393 +
1.394 + pg->post_compact(); // Shared spaces verification.
1.395 +}
