--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/memory/genCollectedHeap.cpp Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,1368 @@
+/*
+ * Copyright 2000-2007 Sun Microsystems, Inc. All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+# include "incls/_precompiled.incl"
+# include "incls/_genCollectedHeap.cpp.incl"
+
+GenCollectedHeap* GenCollectedHeap::_gch;
+NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)
+
+// The set of potentially parallel tasks in strong root scanning.
+enum GCH_process_strong_roots_tasks {
+ // We probably want to parallelize both of these internally, but for now...
+ GCH_PS_younger_gens,
+ // Leave this one last.
+ GCH_PS_NumElements
+};
+
+GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :
+ SharedHeap(policy),
+ _gen_policy(policy),
+ _gen_process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)),
+ _full_collections_completed(0)
+{
+ if (_gen_process_strong_tasks == NULL ||
+ !_gen_process_strong_tasks->valid()) {
+ vm_exit_during_initialization("Failed necessary allocation.");
+ }
+ assert(policy != NULL, "Sanity check");
+ _preloading_shared_classes = false;
+}
+
+jint GenCollectedHeap::initialize() {
+ int i;
+ _n_gens = gen_policy()->number_of_generations();
+
+ // While there are no constraints in the GC code that HeapWordSize
+ // be any particular value, there are multiple other areas in the
+ // system which believe this to be true (e.g. oop->object_size in some
+ // cases incorrectly returns the size in wordSize units rather than
+ // HeapWordSize).
+ guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
+
+ // The heap must be at least as aligned as generations.
+ size_t alignment = Generation::GenGrain;
+
+ _gen_specs = gen_policy()->generations();
+ PermanentGenerationSpec *perm_gen_spec =
+ collector_policy()->permanent_generation();
+
+ // Make sure the sizes are all aligned.
+ for (i = 0; i < _n_gens; i++) {
+ _gen_specs[i]->align(alignment);
+ }
+ perm_gen_spec->align(alignment);
+
+ // If we are dumping the heap, then allocate a wasted block of address
+ // space in order to push the heap to a lower address. This extra
+ // address range allows for other (or larger) libraries to be loaded
+ // without them occupying the space required for the shared spaces.
+
+ if (DumpSharedSpaces) {
+ uintx reserved = 0;
+ uintx block_size = 64*1024*1024;
+ while (reserved < SharedDummyBlockSize) {
+ char* dummy = os::reserve_memory(block_size);
+ reserved += block_size;
+ }
+ }
+
+ // Allocate space for the heap.
+
+ char* heap_address;
+ size_t total_reserved = 0;
+ int n_covered_regions = 0;
+ ReservedSpace heap_rs(0);
+
+ heap_address = allocate(alignment, perm_gen_spec, &total_reserved,
+ &n_covered_regions, &heap_rs);
+
+ if (UseSharedSpaces) {
+ if (!heap_rs.is_reserved() || heap_address != heap_rs.base()) {
+ if (heap_rs.is_reserved()) {
+ heap_rs.release();
+ }
+ FileMapInfo* mapinfo = FileMapInfo::current_info();
+ mapinfo->fail_continue("Unable to reserve shared region.");
+ allocate(alignment, perm_gen_spec, &total_reserved, &n_covered_regions,
+ &heap_rs);
+ }
+ }
+
+ if (!heap_rs.is_reserved()) {
+ vm_shutdown_during_initialization(
+ "Could not reserve enough space for object heap");
+ return JNI_ENOMEM;
+ }
+
+ _reserved = MemRegion((HeapWord*)heap_rs.base(),
+ (HeapWord*)(heap_rs.base() + heap_rs.size()));
+
+ // It is important to do this in a way such that concurrent readers can't
+ // temporarily think somethings in the heap. (Seen this happen in asserts.)
+ _reserved.set_word_size(0);
+ _reserved.set_start((HeapWord*)heap_rs.base());
+ size_t actual_heap_size = heap_rs.size() - perm_gen_spec->misc_data_size()
+ - perm_gen_spec->misc_code_size();
+ _reserved.set_end((HeapWord*)(heap_rs.base() + actual_heap_size));
+
+ _rem_set = collector_policy()->create_rem_set(_reserved, n_covered_regions);
+ set_barrier_set(rem_set()->bs());
+ _gch = this;
+
+ for (i = 0; i < _n_gens; i++) {
+ ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(),
+ UseSharedSpaces, UseSharedSpaces);
+ _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set());
+ heap_rs = heap_rs.last_part(_gen_specs[i]->max_size());
+ }
+ _perm_gen = perm_gen_spec->init(heap_rs, PermSize, rem_set());
+
+ clear_incremental_collection_will_fail();
+ clear_last_incremental_collection_failed();
+
+#ifndef SERIALGC
+ // If we are running CMS, create the collector responsible
+ // for collecting the CMS generations.
+ if (collector_policy()->is_concurrent_mark_sweep_policy()) {
+ bool success = create_cms_collector();
+ if (!success) return JNI_ENOMEM;
+ }
+#endif // SERIALGC
+
+ return JNI_OK;
+}
+
+
+char* GenCollectedHeap::allocate(size_t alignment,
+ PermanentGenerationSpec* perm_gen_spec,
+ size_t* _total_reserved,
+ int* _n_covered_regions,
+ ReservedSpace* heap_rs){
+ const char overflow_msg[] = "The size of the object heap + VM data exceeds "
+ "the maximum representable size";
+
+ // Now figure out the total size.
+ size_t total_reserved = 0;
+ int n_covered_regions = 0;
+ const size_t pageSize = UseLargePages ?
+ os::large_page_size() : os::vm_page_size();
+
+ for (int i = 0; i < _n_gens; i++) {
+ total_reserved += _gen_specs[i]->max_size();
+ if (total_reserved < _gen_specs[i]->max_size()) {
+ vm_exit_during_initialization(overflow_msg);
+ }
+ n_covered_regions += _gen_specs[i]->n_covered_regions();
+ }
+ assert(total_reserved % pageSize == 0, "Gen size");
+ total_reserved += perm_gen_spec->max_size();
+ assert(total_reserved % pageSize == 0, "Perm Gen size");
+
+ if (total_reserved < perm_gen_spec->max_size()) {
+ vm_exit_during_initialization(overflow_msg);
+ }
+ n_covered_regions += perm_gen_spec->n_covered_regions();
+
+ // Add the size of the data area which shares the same reserved area
+ // as the heap, but which is not actually part of the heap.
+ size_t s = perm_gen_spec->misc_data_size() + perm_gen_spec->misc_code_size();
+
+ total_reserved += s;
+ if (total_reserved < s) {
+ vm_exit_during_initialization(overflow_msg);
+ }
+
+ if (UseLargePages) {
+ assert(total_reserved != 0, "total_reserved cannot be 0");
+ total_reserved = round_to(total_reserved, os::large_page_size());
+ if (total_reserved < os::large_page_size()) {
+ vm_exit_during_initialization(overflow_msg);
+ }
+ }
+
+ // Calculate the address at which the heap must reside in order for
+ // the shared data to be at the required address.
+
+ char* heap_address;
+ if (UseSharedSpaces) {
+
+ // Calculate the address of the first word beyond the heap.
+ FileMapInfo* mapinfo = FileMapInfo::current_info();
+ int lr = CompactingPermGenGen::n_regions - 1;
+ size_t capacity = align_size_up(mapinfo->space_capacity(lr), alignment);
+ heap_address = mapinfo->region_base(lr) + capacity;
+
+ // Calculate the address of the first word of the heap.
+ heap_address -= total_reserved;
+ } else {
+ heap_address = NULL; // any address will do.
+ }
+
+ *_total_reserved = total_reserved;
+ *_n_covered_regions = n_covered_regions;
+ *heap_rs = ReservedSpace(total_reserved, alignment,
+ UseLargePages, heap_address);
+
+ return heap_address;
+}
+
+
+void GenCollectedHeap::post_initialize() {
+ SharedHeap::post_initialize();
+ TwoGenerationCollectorPolicy *policy =
+ (TwoGenerationCollectorPolicy *)collector_policy();
+ guarantee(policy->is_two_generation_policy(), "Illegal policy type");
+ DefNewGeneration* def_new_gen = (DefNewGeneration*) get_gen(0);
+ assert(def_new_gen->kind() == Generation::DefNew ||
+ def_new_gen->kind() == Generation::ParNew ||
+ def_new_gen->kind() == Generation::ASParNew,
+ "Wrong generation kind");
+
+ Generation* old_gen = get_gen(1);
+ assert(old_gen->kind() == Generation::ConcurrentMarkSweep ||
+ old_gen->kind() == Generation::ASConcurrentMarkSweep ||
+ old_gen->kind() == Generation::MarkSweepCompact,
+ "Wrong generation kind");
+
+ policy->initialize_size_policy(def_new_gen->eden()->capacity(),
+ old_gen->capacity(),
+ def_new_gen->from()->capacity());
+ policy->initialize_gc_policy_counters();
+}
+
+void GenCollectedHeap::ref_processing_init() {
+ SharedHeap::ref_processing_init();
+ for (int i = 0; i < _n_gens; i++) {
+ _gens[i]->ref_processor_init();
+ }
+}
+
+size_t GenCollectedHeap::capacity() const {
+ size_t res = 0;
+ for (int i = 0; i < _n_gens; i++) {
+ res += _gens[i]->capacity();
+ }
+ return res;
+}
+
+size_t GenCollectedHeap::used() const {
+ size_t res = 0;
+ for (int i = 0; i < _n_gens; i++) {
+ res += _gens[i]->used();
+ }
+ return res;
+}
+
+// Save the "used_region" for generations level and lower,
+// and, if perm is true, for perm gen.
+void GenCollectedHeap::save_used_regions(int level, bool perm) {
+ assert(level < _n_gens, "Illegal level parameter");
+ for (int i = level; i >= 0; i--) {
+ _gens[i]->save_used_region();
+ }
+ if (perm) {
+ perm_gen()->save_used_region();
+ }
+}
+
+size_t GenCollectedHeap::max_capacity() const {
+ size_t res = 0;
+ for (int i = 0; i < _n_gens; i++) {
+ res += _gens[i]->max_capacity();
+ }
+ return res;
+}
+
+// Update the _full_collections_completed counter
+// at the end of a stop-world full GC.
+unsigned int GenCollectedHeap::update_full_collections_completed() {
+ MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
+ assert(_full_collections_completed <= _total_full_collections,
+ "Can't complete more collections than were started");
+ _full_collections_completed = _total_full_collections;
+ ml.notify_all();
+ return _full_collections_completed;
+}
+
+// Update the _full_collections_completed counter, as appropriate,
+// at the end of a concurrent GC cycle. Note the conditional update
+// below to allow this method to be called by a concurrent collector
+// without synchronizing in any manner with the VM thread (which
+// may already have initiated a STW full collection "concurrently").
+unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
+ MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
+ assert((_full_collections_completed <= _total_full_collections) &&
+ (count <= _total_full_collections),
+ "Can't complete more collections than were started");
+ if (count > _full_collections_completed) {
+ _full_collections_completed = count;
+ ml.notify_all();
+ }
+ return _full_collections_completed;
+}
+
+
+#ifndef PRODUCT
+// Override of memory state checking method in CollectedHeap:
+// Some collectors (CMS for example) can't have badHeapWordVal written
+// in the first two words of an object. (For instance , in the case of
+// CMS these words hold state used to synchronize between certain
+// (concurrent) GC steps and direct allocating mutators.)
+// The skip_header_HeapWords() method below, allows us to skip
+// over the requisite number of HeapWord's. Note that (for
+// generational collectors) this means that those many words are
+// skipped in each object, irrespective of the generation in which
+// that object lives. The resultant loss of precision seems to be
+// harmless and the pain of avoiding that imprecision appears somewhat
+// higher than we are prepared to pay for such rudimentary debugging
+// support.
+void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,
+ size_t size) {
+ if (CheckMemoryInitialization && ZapUnusedHeapArea) {
+ // We are asked to check a size in HeapWords,
+ // but the memory is mangled in juint words.
+ juint* start = (juint*) (addr + skip_header_HeapWords());
+ juint* end = (juint*) (addr + size);
+ for (juint* slot = start; slot < end; slot += 1) {
+ assert(*slot == badHeapWordVal,
+ "Found non badHeapWordValue in pre-allocation check");
+ }
+ }
+}
+#endif
+
+HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
+ bool is_tlab,
+ bool first_only) {
+ HeapWord* res;
+ for (int i = 0; i < _n_gens; i++) {
+ if (_gens[i]->should_allocate(size, is_tlab)) {
+ res = _gens[i]->allocate(size, is_tlab);
+ if (res != NULL) return res;
+ else if (first_only) break;
+ }
+ }
+ // Otherwise...
+ return NULL;
+}
+
+HeapWord* GenCollectedHeap::mem_allocate(size_t size,
+ bool is_large_noref,
+ bool is_tlab,
+ bool* gc_overhead_limit_was_exceeded) {
+ return collector_policy()->mem_allocate_work(size,
+ is_tlab,
+ gc_overhead_limit_was_exceeded);
+}
+
+bool GenCollectedHeap::must_clear_all_soft_refs() {
+ return _gc_cause == GCCause::_last_ditch_collection;
+}
+
+bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
+ return (cause == GCCause::_java_lang_system_gc ||
+ cause == GCCause::_gc_locker) &&
+ UseConcMarkSweepGC && ExplicitGCInvokesConcurrent;
+}
+
+void GenCollectedHeap::do_collection(bool full,
+ bool clear_all_soft_refs,
+ size_t size,
+ bool is_tlab,
+ int max_level) {
+ bool prepared_for_verification = false;
+ ResourceMark rm;
+ DEBUG_ONLY(Thread* my_thread = Thread::current();)
+
+ assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
+ assert(my_thread->is_VM_thread() ||
+ my_thread->is_ConcurrentGC_thread(),
+ "incorrect thread type capability");
+ assert(Heap_lock->is_locked(), "the requesting thread should have the Heap_lock");
+ guarantee(!is_gc_active(), "collection is not reentrant");
+ assert(max_level < n_gens(), "sanity check");
+
+ if (GC_locker::check_active_before_gc()) {
+ return; // GC is disabled (e.g. JNI GetXXXCritical operation)
+ }
+
+ const size_t perm_prev_used = perm_gen()->used();
+
+ if (PrintHeapAtGC) {
+ Universe::print_heap_before_gc();
+ if (Verbose) {
+ gclog_or_tty->print_cr("GC Cause: %s", GCCause::to_string(gc_cause()));
+ }
+ }
+
+ {
+ FlagSetting fl(_is_gc_active, true);
+
+ bool complete = full && (max_level == (n_gens()-1));
+ const char* gc_cause_str = "GC ";
+ if (complete) {
+ GCCause::Cause cause = gc_cause();
+ if (cause == GCCause::_java_lang_system_gc) {
+ gc_cause_str = "Full GC (System) ";
+ } else {
+ gc_cause_str = "Full GC ";
+ }
+ }
+ gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
+ TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
+ TraceTime t(gc_cause_str, PrintGCDetails, false, gclog_or_tty);
+
+ gc_prologue(complete);
+ increment_total_collections(complete);
+
+ size_t gch_prev_used = used();
+
+ int starting_level = 0;
+ if (full) {
+ // Search for the oldest generation which will collect all younger
+ // generations, and start collection loop there.
+ for (int i = max_level; i >= 0; i--) {
+ if (_gens[i]->full_collects_younger_generations()) {
+ starting_level = i;
+ break;
+ }
+ }
+ }
+
+ bool must_restore_marks_for_biased_locking = false;
+
+ int max_level_collected = starting_level;
+ for (int i = starting_level; i <= max_level; i++) {
+ if (_gens[i]->should_collect(full, size, is_tlab)) {
+ // Timer for individual generations. Last argument is false: no CR
+ TraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, gclog_or_tty);
+ TraceCollectorStats tcs(_gens[i]->counters());
+ TraceMemoryManagerStats tmms(_gens[i]->kind());
+
+ size_t prev_used = _gens[i]->used();
+ _gens[i]->stat_record()->invocations++;
+ _gens[i]->stat_record()->accumulated_time.start();
+
+ if (PrintGC && Verbose) {
+ gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT,
+ i,
+ _gens[i]->stat_record()->invocations,
+ size*HeapWordSize);
+ }
+
+ if (VerifyBeforeGC && i >= VerifyGCLevel &&
+ total_collections() >= VerifyGCStartAt) {
+ HandleMark hm; // Discard invalid handles created during verification
+ if (!prepared_for_verification) {
+ prepare_for_verify();
+ prepared_for_verification = true;
+ }
+ gclog_or_tty->print(" VerifyBeforeGC:");
+ Universe::verify(true);
+ }
+ COMPILER2_PRESENT(DerivedPointerTable::clear());
+
+ if (!must_restore_marks_for_biased_locking &&
+ _gens[i]->performs_in_place_marking()) {
+ // We perform this mark word preservation work lazily
+ // because it's only at this point that we know whether we
+ // absolutely have to do it; we want to avoid doing it for
+ // scavenge-only collections where it's unnecessary
+ must_restore_marks_for_biased_locking = true;
+ BiasedLocking::preserve_marks();
+ }
+
+ // Do collection work
+ {
+ // Note on ref discovery: For what appear to be historical reasons,
+ // GCH enables and disabled (by enqueing) refs discovery.
+ // In the future this should be moved into the generation's
+ // collect method so that ref discovery and enqueueing concerns
+ // are local to a generation. The collect method could return
+ // an appropriate indication in the case that notification on
+ // the ref lock was needed. This will make the treatment of
+ // weak refs more uniform (and indeed remove such concerns
+ // from GCH). XXX
+
+ HandleMark hm; // Discard invalid handles created during gc
+ save_marks(); // save marks for all gens
+ // We want to discover references, but not process them yet.
+ // This mode is disabled in process_discovered_references if the
+ // generation does some collection work, or in
+ // enqueue_discovered_references if the generation returns
+ // without doing any work.
+ ReferenceProcessor* rp = _gens[i]->ref_processor();
+ // If the discovery of ("weak") refs in this generation is
+ // atomic wrt other collectors in this configuration, we
+ // are guaranteed to have empty discovered ref lists.
+ if (rp->discovery_is_atomic()) {
+ rp->verify_no_references_recorded();
+ rp->enable_discovery();
+ } else {
+ // collect() will enable discovery as appropriate
+ }
+ _gens[i]->collect(full, clear_all_soft_refs, size, is_tlab);
+ if (!rp->enqueuing_is_done()) {
+ rp->enqueue_discovered_references();
+ } else {
+ rp->set_enqueuing_is_done(false);
+ }
+ rp->verify_no_references_recorded();
+ }
+ max_level_collected = i;
+
+ // Determine if allocation request was met.
+ if (size > 0) {
+ if (!is_tlab || _gens[i]->supports_tlab_allocation()) {
+ if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) {
+ size = 0;
+ }
+ }
+ }
+
+ COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
+
+ _gens[i]->stat_record()->accumulated_time.stop();
+
+ update_gc_stats(i, full);
+
+ if (VerifyAfterGC && i >= VerifyGCLevel &&
+ total_collections() >= VerifyGCStartAt) {
+ HandleMark hm; // Discard invalid handles created during verification
+ gclog_or_tty->print(" VerifyAfterGC:");
+ Universe::verify(false);
+ }
+
+ if (PrintGCDetails) {
+ gclog_or_tty->print(":");
+ _gens[i]->print_heap_change(prev_used);
+ }
+ }
+ }
+
+ // Update "complete" boolean wrt what actually transpired --
+ // for instance, a promotion failure could have led to
+ // a whole heap collection.
+ complete = complete || (max_level_collected == n_gens() - 1);
+
+ if (PrintGCDetails) {
+ print_heap_change(gch_prev_used);
+
+ // Print perm gen info for full GC with PrintGCDetails flag.
+ if (complete) {
+ print_perm_heap_change(perm_prev_used);
+ }
+ }
+
+ for (int j = max_level_collected; j >= 0; j -= 1) {
+ // Adjust generation sizes.
+ _gens[j]->compute_new_size();
+ }
+
+ if (complete) {
+ // Ask the permanent generation to adjust size for full collections
+ perm()->compute_new_size();
+ update_full_collections_completed();
+ }
+
+ // Track memory usage and detect low memory after GC finishes
+ MemoryService::track_memory_usage();
+
+ gc_epilogue(complete);
+
+ if (must_restore_marks_for_biased_locking) {
+ BiasedLocking::restore_marks();
+ }
+ }
+
+ AdaptiveSizePolicy* sp = gen_policy()->size_policy();
+ AdaptiveSizePolicyOutput(sp, total_collections());
+
+ if (PrintHeapAtGC) {
+ Universe::print_heap_after_gc();
+ }
+
+ if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
+ tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
+ vm_exit(-1);
+ }
+}
+
+HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
+ return collector_policy()->satisfy_failed_allocation(size, is_tlab);
+}
+
+void GenCollectedHeap::set_par_threads(int t) {
+ SharedHeap::set_par_threads(t);
+ _gen_process_strong_tasks->set_par_threads(t);
+}
+
+class AssertIsPermClosure: public OopClosure {
+public:
+ void do_oop(oop* p) {
+ assert((*p) == NULL || (*p)->is_perm(), "Referent should be perm.");
+ }
+};
+static AssertIsPermClosure assert_is_perm_closure;
+
+void GenCollectedHeap::
+gen_process_strong_roots(int level,
+ bool younger_gens_as_roots,
+ bool collecting_perm_gen,
+ SharedHeap::ScanningOption so,
+ OopsInGenClosure* older_gens,
+ OopsInGenClosure* not_older_gens) {
+ // General strong roots.
+ SharedHeap::process_strong_roots(collecting_perm_gen, so,
+ not_older_gens, older_gens);
+
+ if (younger_gens_as_roots) {
+ if (!_gen_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) {
+ for (int i = 0; i < level; i++) {
+ not_older_gens->set_generation(_gens[i]);
+ _gens[i]->oop_iterate(not_older_gens);
+ }
+ not_older_gens->reset_generation();
+ }
+ }
+ // When collection is parallel, all threads get to cooperate to do
+ // older-gen scanning.
+ for (int i = level+1; i < _n_gens; i++) {
+ older_gens->set_generation(_gens[i]);
+ rem_set()->younger_refs_iterate(_gens[i], older_gens);
+ older_gens->reset_generation();
+ }
+
+ _gen_process_strong_tasks->all_tasks_completed();
+}
+
+void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure,
+ OopClosure* non_root_closure) {
+ SharedHeap::process_weak_roots(root_closure, non_root_closure);
+ // "Local" "weak" refs
+ for (int i = 0; i < _n_gens; i++) {
+ _gens[i]->ref_processor()->weak_oops_do(root_closure);
+ }
+}
+
+#define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix) \
+void GenCollectedHeap:: \
+oop_since_save_marks_iterate(int level, \
+ OopClosureType* cur, \
+ OopClosureType* older) { \
+ _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur); \
+ for (int i = level+1; i < n_gens(); i++) { \
+ _gens[i]->oop_since_save_marks_iterate##nv_suffix(older); \
+ } \
+ perm_gen()->oop_since_save_marks_iterate##nv_suffix(older); \
+}
+
+ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
+
+#undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
+
+bool GenCollectedHeap::no_allocs_since_save_marks(int level) {
+ for (int i = level; i < _n_gens; i++) {
+ if (!_gens[i]->no_allocs_since_save_marks()) return false;
+ }
+ return perm_gen()->no_allocs_since_save_marks();
+}
+
+bool GenCollectedHeap::supports_inline_contig_alloc() const {
+ return _gens[0]->supports_inline_contig_alloc();
+}
+
+HeapWord** GenCollectedHeap::top_addr() const {
+ return _gens[0]->top_addr();
+}
+
+HeapWord** GenCollectedHeap::end_addr() const {
+ return _gens[0]->end_addr();
+}
+
+size_t GenCollectedHeap::unsafe_max_alloc() {
+ return _gens[0]->unsafe_max_alloc_nogc();
+}
+
+// public collection interfaces
+
+void GenCollectedHeap::collect(GCCause::Cause cause) {
+ if (should_do_concurrent_full_gc(cause)) {
+#ifndef SERIALGC
+ // mostly concurrent full collection
+ collect_mostly_concurrent(cause);
+#else // SERIALGC
+ ShouldNotReachHere();
+#endif // SERIALGC
+ } else {
+#ifdef ASSERT
+ if (cause == GCCause::_scavenge_alot) {
+ // minor collection only
+ collect(cause, 0);
+ } else {
+ // Stop-the-world full collection
+ collect(cause, n_gens() - 1);
+ }
+#else
+ // Stop-the-world full collection
+ collect(cause, n_gens() - 1);
+#endif
+ }
+}
+
+void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) {
+ // The caller doesn't have the Heap_lock
+ assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
+ MutexLocker ml(Heap_lock);
+ collect_locked(cause, max_level);
+}
+
+// This interface assumes that it's being called by the
+// vm thread. It collects the heap assuming that the
+// heap lock is already held and that we are executing in
+// the context of the vm thread.
+void GenCollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
+ assert(Thread::current()->is_VM_thread(), "Precondition#1");
+ assert(Heap_lock->is_locked(), "Precondition#2");
+ GCCauseSetter gcs(this, cause);
+ switch (cause) {
+ case GCCause::_heap_inspection:
+ case GCCause::_heap_dump: {
+ HandleMark hm;
+ do_full_collection(false, // don't clear all soft refs
+ n_gens() - 1);
+ break;
+ }
+ default: // XXX FIX ME
+ ShouldNotReachHere(); // Unexpected use of this function
+ }
+}
+
+void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
+ // The caller has the Heap_lock
+ assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
+ collect_locked(cause, n_gens() - 1);
+}
+
+// this is the private collection interface
+// The Heap_lock is expected to be held on entry.
+
+void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) {
+ if (_preloading_shared_classes) {
+ warning("\nThe permanent generation is not large enough to preload "
+ "requested classes.\nUse -XX:PermSize= to increase the initial "
+ "size of the permanent generation.\n");
+ vm_exit(2);
+ }
+ // Read the GC count while holding the Heap_lock
+ unsigned int gc_count_before = total_collections();
+ unsigned int full_gc_count_before = total_full_collections();
+ {
+ MutexUnlocker mu(Heap_lock); // give up heap lock, execute gets it back
+ VM_GenCollectFull op(gc_count_before, full_gc_count_before,
+ cause, max_level);
+ VMThread::execute(&op);
+ }
+}
+
+#ifndef SERIALGC
+bool GenCollectedHeap::create_cms_collector() {
+
+ assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) ||
+ (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)) &&
+ _perm_gen->as_gen()->kind() == Generation::ConcurrentMarkSweep,
+ "Unexpected generation kinds");
+ // Skip two header words in the block content verification
+ NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
+ CMSCollector* collector = new CMSCollector(
+ (ConcurrentMarkSweepGeneration*)_gens[1],
+ (ConcurrentMarkSweepGeneration*)_perm_gen->as_gen(),
+ _rem_set->as_CardTableRS(),
+ (ConcurrentMarkSweepPolicy*) collector_policy());
+
+ if (collector == NULL || !collector->completed_initialization()) {
+ if (collector) {
+ delete collector; // Be nice in embedded situation
+ }
+ vm_shutdown_during_initialization("Could not create CMS collector");
+ return false;
+ }
+ return true; // success
+}
+
+void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
+ assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
+
+ MutexLocker ml(Heap_lock);
+ // Read the GC counts while holding the Heap_lock
+ unsigned int full_gc_count_before = total_full_collections();
+ unsigned int gc_count_before = total_collections();
+ {
+ MutexUnlocker mu(Heap_lock);
+ VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
+ VMThread::execute(&op);
+ }
+}
+#endif // SERIALGC
+
+
+void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
+ int max_level) {
+ int local_max_level;
+ if (!incremental_collection_will_fail() &&
+ gc_cause() == GCCause::_gc_locker) {
+ local_max_level = 0;
+ } else {
+ local_max_level = max_level;
+ }
+
+ do_collection(true /* full */,
+ clear_all_soft_refs /* clear_all_soft_refs */,
+ 0 /* size */,
+ false /* is_tlab */,
+ local_max_level /* max_level */);
+ // Hack XXX FIX ME !!!
+ // A scavenge may not have been attempted, or may have
+ // been attempted and failed, because the old gen was too full
+ if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker &&
+ incremental_collection_will_fail()) {
+ if (PrintGCDetails) {
+ gclog_or_tty->print_cr("GC locker: Trying a full collection "
+ "because scavenge failed");
+ }
+ // This time allow the old gen to be collected as well
+ do_collection(true /* full */,
+ clear_all_soft_refs /* clear_all_soft_refs */,
+ 0 /* size */,
+ false /* is_tlab */,
+ n_gens() - 1 /* max_level */);
+ }
+}
+
+// Returns "TRUE" iff "p" points into the allocated area of the heap.
+bool GenCollectedHeap::is_in(const void* p) const {
+ #ifndef ASSERT
+ guarantee(VerifyBeforeGC ||
+ VerifyDuringGC ||
+ VerifyBeforeExit ||
+ VerifyAfterGC, "too expensive");
+ #endif
+ // This might be sped up with a cache of the last generation that
+ // answered yes.
+ for (int i = 0; i < _n_gens; i++) {
+ if (_gens[i]->is_in(p)) return true;
+ }
+ if (_perm_gen->as_gen()->is_in(p)) return true;
+ // Otherwise...
+ return false;
+}
+
+// Returns "TRUE" iff "p" points into the allocated area of the heap.
+bool GenCollectedHeap::is_in_youngest(void* p) {
+ return _gens[0]->is_in(p);
+}
+
+void GenCollectedHeap::oop_iterate(OopClosure* cl) {
+ for (int i = 0; i < _n_gens; i++) {
+ _gens[i]->oop_iterate(cl);
+ }
+}
+
+void GenCollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl) {
+ for (int i = 0; i < _n_gens; i++) {
+ _gens[i]->oop_iterate(mr, cl);
+ }
+}
+
+void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
+ for (int i = 0; i < _n_gens; i++) {
+ _gens[i]->object_iterate(cl);
+ }
+ perm_gen()->object_iterate(cl);
+}
+
+void GenCollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
+ for (int i = 0; i < _n_gens; i++) {
+ _gens[i]->object_iterate_since_last_GC(cl);
+ }
+}
+
+Space* GenCollectedHeap::space_containing(const void* addr) const {
+ for (int i = 0; i < _n_gens; i++) {
+ Space* res = _gens[i]->space_containing(addr);
+ if (res != NULL) return res;
+ }
+ Space* res = perm_gen()->space_containing(addr);
+ if (res != NULL) return res;
+ // Otherwise...
+ assert(false, "Could not find containing space");
+ return NULL;
+}
+
+
+HeapWord* GenCollectedHeap::block_start(const void* addr) const {
+ assert(is_in_reserved(addr), "block_start of address outside of heap");
+ for (int i = 0; i < _n_gens; i++) {
+ if (_gens[i]->is_in_reserved(addr)) {
+ assert(_gens[i]->is_in(addr),
+ "addr should be in allocated part of generation");
+ return _gens[i]->block_start(addr);
+ }
+ }
+ if (perm_gen()->is_in_reserved(addr)) {
+ assert(perm_gen()->is_in(addr),
+ "addr should be in allocated part of perm gen");
+ return perm_gen()->block_start(addr);
+ }
+ assert(false, "Some generation should contain the address");
+ return NULL;
+}
+
+size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
+ assert(is_in_reserved(addr), "block_size of address outside of heap");
+ for (int i = 0; i < _n_gens; i++) {
+ if (_gens[i]->is_in_reserved(addr)) {
+ assert(_gens[i]->is_in(addr),
+ "addr should be in allocated part of generation");
+ return _gens[i]->block_size(addr);
+ }
+ }
+ if (perm_gen()->is_in_reserved(addr)) {
+ assert(perm_gen()->is_in(addr),
+ "addr should be in allocated part of perm gen");
+ return perm_gen()->block_size(addr);
+ }
+ assert(false, "Some generation should contain the address");
+ return 0;
+}
+
+bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
+ assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
+ assert(block_start(addr) == addr, "addr must be a block start");
+ for (int i = 0; i < _n_gens; i++) {
+ if (_gens[i]->is_in_reserved(addr)) {
+ return _gens[i]->block_is_obj(addr);
+ }
+ }
+ if (perm_gen()->is_in_reserved(addr)) {
+ return perm_gen()->block_is_obj(addr);
+ }
+ assert(false, "Some generation should contain the address");
+ return false;
+}
+
+bool GenCollectedHeap::supports_tlab_allocation() const {
+ for (int i = 0; i < _n_gens; i += 1) {
+ if (_gens[i]->supports_tlab_allocation()) {
+ return true;
+ }
+ }
+ return false;
+}
+
+size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
+ size_t result = 0;
+ for (int i = 0; i < _n_gens; i += 1) {
+ if (_gens[i]->supports_tlab_allocation()) {
+ result += _gens[i]->tlab_capacity();
+ }
+ }
+ return result;
+}
+
+size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
+ size_t result = 0;
+ for (int i = 0; i < _n_gens; i += 1) {
+ if (_gens[i]->supports_tlab_allocation()) {
+ result += _gens[i]->unsafe_max_tlab_alloc();
+ }
+ }
+ return result;
+}
+
+HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
+ bool gc_overhead_limit_was_exceeded;
+ HeapWord* result = mem_allocate(size /* size */,
+ false /* is_large_noref */,
+ true /* is_tlab */,
+ &gc_overhead_limit_was_exceeded);
+ return result;
+}
+
+// Requires "*prev_ptr" to be non-NULL. Deletes and a block of minimal size
+// from the list headed by "*prev_ptr".
+static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
+ bool first = true;
+ size_t min_size = 0; // "first" makes this conceptually infinite.
+ ScratchBlock **smallest_ptr, *smallest;
+ ScratchBlock *cur = *prev_ptr;
+ while (cur) {
+ assert(*prev_ptr == cur, "just checking");
+ if (first || cur->num_words < min_size) {
+ smallest_ptr = prev_ptr;
+ smallest = cur;
+ min_size = smallest->num_words;
+ first = false;
+ }
+ prev_ptr = &cur->next;
+ cur = cur->next;
+ }
+ smallest = *smallest_ptr;
+ *smallest_ptr = smallest->next;
+ return smallest;
+}
+
+// Sort the scratch block list headed by res into decreasing size order,
+// and set "res" to the result.
+static void sort_scratch_list(ScratchBlock*& list) {
+ ScratchBlock* sorted = NULL;
+ ScratchBlock* unsorted = list;
+ while (unsorted) {
+ ScratchBlock *smallest = removeSmallestScratch(&unsorted);
+ smallest->next = sorted;
+ sorted = smallest;
+ }
+ list = sorted;
+}
+
+ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
+ size_t max_alloc_words) {
+ ScratchBlock* res = NULL;
+ for (int i = 0; i < _n_gens; i++) {
+ _gens[i]->contribute_scratch(res, requestor, max_alloc_words);
+ }
+ sort_scratch_list(res);
+ return res;
+}
+
+size_t GenCollectedHeap::large_typearray_limit() {
+ return gen_policy()->large_typearray_limit();
+}
+
+class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
+ void do_generation(Generation* gen) {
+ gen->prepare_for_verify();
+ }
+};
+
+void GenCollectedHeap::prepare_for_verify() {
+ ensure_parsability(false); // no need to retire TLABs
+ GenPrepareForVerifyClosure blk;
+ generation_iterate(&blk, false);
+ perm_gen()->prepare_for_verify();
+}
+
+
+void GenCollectedHeap::generation_iterate(GenClosure* cl,
+ bool old_to_young) {
+ if (old_to_young) {
+ for (int i = _n_gens-1; i >= 0; i--) {
+ cl->do_generation(_gens[i]);
+ }
+ } else {
+ for (int i = 0; i < _n_gens; i++) {
+ cl->do_generation(_gens[i]);
+ }
+ }
+}
+
+void GenCollectedHeap::space_iterate(SpaceClosure* cl) {
+ for (int i = 0; i < _n_gens; i++) {
+ _gens[i]->space_iterate(cl, true);
+ }
+ perm_gen()->space_iterate(cl, true);
+}
+
+bool GenCollectedHeap::is_maximal_no_gc() const {
+ for (int i = 0; i < _n_gens; i++) { // skip perm gen
+ if (!_gens[i]->is_maximal_no_gc()) {
+ return false;
+ }
+ }
+ return true;
+}
+
+void GenCollectedHeap::save_marks() {
+ for (int i = 0; i < _n_gens; i++) {
+ _gens[i]->save_marks();
+ }
+ perm_gen()->save_marks();
+}
+
+void GenCollectedHeap::compute_new_generation_sizes(int collectedGen) {
+ for (int i = 0; i <= collectedGen; i++) {
+ _gens[i]->compute_new_size();
+ }
+}
+
+GenCollectedHeap* GenCollectedHeap::heap() {
+ assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()");
+ assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap");
+ return _gch;
+}
+
+
+void GenCollectedHeap::prepare_for_compaction() {
+ Generation* scanning_gen = _gens[_n_gens-1];
+ // Start by compacting into same gen.
+ CompactPoint cp(scanning_gen, NULL, NULL);
+ while (scanning_gen != NULL) {
+ scanning_gen->prepare_for_compaction(&cp);
+ scanning_gen = prev_gen(scanning_gen);
+ }
+}
+
+GCStats* GenCollectedHeap::gc_stats(int level) const {
+ return _gens[level]->gc_stats();
+}
+
+void GenCollectedHeap::verify(bool allow_dirty, bool silent) {
+ if (!silent) {
+ gclog_or_tty->print("permgen ");
+ }
+ perm_gen()->verify(allow_dirty);
+ for (int i = _n_gens-1; i >= 0; i--) {
+ Generation* g = _gens[i];
+ if (!silent) {
+ gclog_or_tty->print(g->name());
+ gclog_or_tty->print(" ");
+ }
+ g->verify(allow_dirty);
+ }
+ if (!silent) {
+ gclog_or_tty->print("remset ");
+ }
+ rem_set()->verify();
+ if (!silent) {
+ gclog_or_tty->print("ref_proc ");
+ }
+ ReferenceProcessor::verify();
+}
+
+void GenCollectedHeap::print() const { print_on(tty); }
+void GenCollectedHeap::print_on(outputStream* st) const {
+ for (int i = 0; i < _n_gens; i++) {
+ _gens[i]->print_on(st);
+ }
+ perm_gen()->print_on(st);
+}
+
+void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
+ if (workers() != NULL) {
+ workers()->threads_do(tc);
+ }
+#ifndef SERIALGC
+ if (UseConcMarkSweepGC) {
+ ConcurrentMarkSweepThread::threads_do(tc);
+ }
+#endif // SERIALGC
+}
+
+void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
+#ifndef SERIALGC
+ if (UseParNewGC) {
+ workers()->print_worker_threads_on(st);
+ }
+ if (UseConcMarkSweepGC) {
+ ConcurrentMarkSweepThread::print_all_on(st);
+ }
+#endif // SERIALGC
+}
+
+void GenCollectedHeap::print_tracing_info() const {
+ if (TraceGen0Time) {
+ get_gen(0)->print_summary_info();
+ }
+ if (TraceGen1Time) {
+ get_gen(1)->print_summary_info();
+ }
+}
+
+void GenCollectedHeap::print_heap_change(size_t prev_used) const {
+ if (PrintGCDetails && Verbose) {
+ gclog_or_tty->print(" " SIZE_FORMAT
+ "->" SIZE_FORMAT
+ "(" SIZE_FORMAT ")",
+ prev_used, used(), capacity());
+ } else {
+ gclog_or_tty->print(" " SIZE_FORMAT "K"
+ "->" SIZE_FORMAT "K"
+ "(" SIZE_FORMAT "K)",
+ prev_used / K, used() / K, capacity() / K);
+ }
+}
+
+//New method to print perm gen info with PrintGCDetails flag
+void GenCollectedHeap::print_perm_heap_change(size_t perm_prev_used) const {
+ gclog_or_tty->print(", [%s :", perm_gen()->short_name());
+ perm_gen()->print_heap_change(perm_prev_used);
+ gclog_or_tty->print("]");
+}
+
+class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
+ private:
+ bool _full;
+ public:
+ void do_generation(Generation* gen) {
+ gen->gc_prologue(_full);
+ }
+ GenGCPrologueClosure(bool full) : _full(full) {};
+};
+
+void GenCollectedHeap::gc_prologue(bool full) {
+ assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
+
+ always_do_update_barrier = false;
+ // Fill TLAB's and such
+ CollectedHeap::accumulate_statistics_all_tlabs();
+ ensure_parsability(true); // retire TLABs
+
+ // Call allocation profiler
+ AllocationProfiler::iterate_since_last_gc();
+ // Walk generations
+ GenGCPrologueClosure blk(full);
+ generation_iterate(&blk, false); // not old-to-young.
+ perm_gen()->gc_prologue(full);
+};
+
+class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
+ private:
+ bool _full;
+ public:
+ void do_generation(Generation* gen) {
+ gen->gc_epilogue(_full);
+ }
+ GenGCEpilogueClosure(bool full) : _full(full) {};
+};
+
+void GenCollectedHeap::gc_epilogue(bool full) {
+ // Remember if a partial collection of the heap failed, and
+ // we did a complete collection.
+ if (full && incremental_collection_will_fail()) {
+ set_last_incremental_collection_failed();
+ } else {
+ clear_last_incremental_collection_failed();
+ }
+ // Clear the flag, if set; the generation gc_epilogues will set the
+ // flag again if the condition persists despite the collection.
+ clear_incremental_collection_will_fail();
+
+#ifdef COMPILER2
+ assert(DerivedPointerTable::is_empty(), "derived pointer present");
+ size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
+ guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
+#endif /* COMPILER2 */
+
+ resize_all_tlabs();
+
+ GenGCEpilogueClosure blk(full);
+ generation_iterate(&blk, false); // not old-to-young.
+ perm_gen()->gc_epilogue(full);
+
+ always_do_update_barrier = UseConcMarkSweepGC;
+};
+
+class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
+ public:
+ void do_generation(Generation* gen) {
+ gen->ensure_parsability();
+ }
+};
+
+void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
+ CollectedHeap::ensure_parsability(retire_tlabs);
+ GenEnsureParsabilityClosure ep_cl;
+ generation_iterate(&ep_cl, false);
+ perm_gen()->ensure_parsability();
+}
+
+oop GenCollectedHeap::handle_failed_promotion(Generation* gen,
+ oop obj,
+ size_t obj_size,
+ oop* ref) {
+ assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
+ HeapWord* result = NULL;
+
+ // First give each higher generation a chance to allocate the promoted object.
+ Generation* allocator = next_gen(gen);
+ if (allocator != NULL) {
+ do {
+ result = allocator->allocate(obj_size, false);
+ } while (result == NULL && (allocator = next_gen(allocator)) != NULL);
+ }
+
+ if (result == NULL) {
+ // Then give gen and higher generations a chance to expand and allocate the
+ // object.
+ do {
+ result = gen->expand_and_allocate(obj_size, false);
+ } while (result == NULL && (gen = next_gen(gen)) != NULL);
+ }
+
+ if (result != NULL) {
+ Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
+ }
+ return oop(result);
+}
+
+class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
+ jlong _time; // in ms
+ jlong _now; // in ms
+
+ public:
+ GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
+
+ jlong time() { return _time; }
+
+ void do_generation(Generation* gen) {
+ _time = MIN2(_time, gen->time_of_last_gc(_now));
+ }
+};
+
+jlong GenCollectedHeap::millis_since_last_gc() {
+ jlong now = os::javaTimeMillis();
+ GenTimeOfLastGCClosure tolgc_cl(now);
+ // iterate over generations getting the oldest
+ // time that a generation was collected
+ generation_iterate(&tolgc_cl, false);
+ tolgc_cl.do_generation(perm_gen());
+ // XXX Despite the assert above, since javaTimeMillis()
+ // doesnot guarantee monotonically increasing return
+ // values (note, i didn't say "strictly monotonic"),
+ // we need to guard against getting back a time
+ // later than now. This should be fixed by basing
+ // on someting like gethrtime() which guarantees
+ // monotonicity. Note that cond_wait() is susceptible
+ // to a similar problem, because its interface is
+ // based on absolute time in the form of the
+ // system time's notion of UCT. See also 4506635
+ // for yet another problem of similar nature. XXX
+ jlong retVal = now - tolgc_cl.time();
+ if (retVal < 0) {
+ NOT_PRODUCT(warning("time warp: %d", retVal);)
+ return 0;
+ }
+ return retVal;
+}