/*
* Copyright 2001-2009 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/_g1MarkSweep.cpp.incl"
class HeapRegion;
void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
bool clear_all_softrefs) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
// hook up weak ref data so it can be used during Mark-Sweep
assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
assert(rp != NULL, "should be non-NULL");
GenMarkSweep::_ref_processor = rp;
rp->setup_policy(clear_all_softrefs);
// When collecting the permanent generation methodOops may be moving,
// so we either have to flush all bcp data or convert it into bci.
CodeCache::gc_prologue();
Threads::gc_prologue();
// Increment the invocation count for the permanent generation, since it is
// implicitly collected whenever we do a full mark sweep collection.
SharedHeap* sh = SharedHeap::heap();
sh->perm_gen()->stat_record()->invocations++;
bool marked_for_unloading = false;
allocate_stacks();
// We should save the marks of the currently locked biased monitors.
// The marking doesn't preserve the marks of biased objects.
BiasedLocking::preserve_marks();
mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
if (VerifyDuringGC) {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
g1h->checkConcurrentMark();
}
mark_sweep_phase2();
// Don't add any more derived pointers during phase3
COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
mark_sweep_phase3();
mark_sweep_phase4();
GenMarkSweep::restore_marks();
BiasedLocking::restore_marks();
GenMarkSweep::deallocate_stacks();
// We must invalidate the perm-gen rs, so that it gets rebuilt.
GenRemSet* rs = sh->rem_set();
rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/);
// "free at last gc" is calculated from these.
// CHF: cheating for now!!!
// Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
// Universe::set_heap_used_at_last_gc(Universe::heap()->used());
Threads::gc_epilogue();
CodeCache::gc_epilogue();
// refs processing: clean slate
GenMarkSweep::_ref_processor = NULL;
}
void G1MarkSweep::allocate_stacks() {
GenMarkSweep::_preserved_count_max = 0;
GenMarkSweep::_preserved_marks = NULL;
GenMarkSweep::_preserved_count = 0;
GenMarkSweep::_preserved_mark_stack = NULL;
GenMarkSweep::_preserved_oop_stack = NULL;
GenMarkSweep::_marking_stack =
new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
int size = SystemDictionary::number_of_classes() * 2;
GenMarkSweep::_revisit_klass_stack =
new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true);
// (#klass/k)^2 for k ~ 10 appears a better fit, but this will have to do
// for now until we have a chance to work out a more optimal setting.
GenMarkSweep::_revisit_mdo_stack =
new (ResourceObj::C_HEAP) GrowableArray<DataLayout*>(size*2, true);
}
void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
bool clear_all_softrefs) {
// Recursively traverse all live objects and mark them
EventMark m("1 mark object");
TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
GenMarkSweep::trace(" 1");
SharedHeap* sh = SharedHeap::heap();
sh->process_strong_roots(true, // activeate StrongRootsScope
true, // Collecting permanent generation.
SharedHeap::SO_SystemClasses,
&GenMarkSweep::follow_root_closure,
&GenMarkSweep::follow_code_root_closure,
&GenMarkSweep::follow_root_closure);
// Process reference objects found during marking
ReferenceProcessor* rp = GenMarkSweep::ref_processor();
rp->setup_policy(clear_all_softrefs);
rp->process_discovered_references(&GenMarkSweep::is_alive,
&GenMarkSweep::keep_alive,
&GenMarkSweep::follow_stack_closure,
NULL);
// Follow system dictionary roots and unload classes
bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
assert(GenMarkSweep::_marking_stack->is_empty(),
"stack should be empty by now");
// Follow code cache roots (has to be done after system dictionary,
// assumes all live klasses are marked)
CodeCache::do_unloading(&GenMarkSweep::is_alive,
&GenMarkSweep::keep_alive,
purged_class);
GenMarkSweep::follow_stack();
// Update subklass/sibling/implementor links of live klasses
GenMarkSweep::follow_weak_klass_links();
assert(GenMarkSweep::_marking_stack->is_empty(),
"stack should be empty by now");
// Visit memoized MDO's and clear any unmarked weak refs
GenMarkSweep::follow_mdo_weak_refs();
assert(GenMarkSweep::_marking_stack->is_empty(), "just drained");
// Visit symbol and interned string tables and delete unmarked oops
SymbolTable::unlink(&GenMarkSweep::is_alive);
StringTable::unlink(&GenMarkSweep::is_alive);
assert(GenMarkSweep::_marking_stack->is_empty(),
"stack should be empty by now");
}
class G1PrepareCompactClosure: public HeapRegionClosure {
ModRefBarrierSet* _mrbs;
CompactPoint _cp;
void free_humongous_region(HeapRegion* hr) {
HeapWord* bot = hr->bottom();
HeapWord* end = hr->end();
assert(hr->startsHumongous(),
"Only the start of a humongous region should be freed.");
G1CollectedHeap::heap()->free_region(hr);
hr->prepare_for_compaction(&_cp);
// Also clear the part of the card table that will be unused after
// compaction.
_mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
}
public:
G1PrepareCompactClosure(CompactibleSpace* cs) :
_cp(NULL, cs, cs->initialize_threshold()),
_mrbs(G1CollectedHeap::heap()->mr_bs())
{}
bool doHeapRegion(HeapRegion* hr) {
if (hr->isHumongous()) {
if (hr->startsHumongous()) {
oop obj = oop(hr->bottom());
if (obj->is_gc_marked()) {
obj->forward_to(obj);
} else {
free_humongous_region(hr);
}
} else {
assert(hr->continuesHumongous(), "Invalid humongous.");
}
} else {
hr->prepare_for_compaction(&_cp);
// Also clear the part of the card table that will be unused after
// compaction.
_mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
}
return false;
}
};
// Finds the first HeapRegion.
class FindFirstRegionClosure: public HeapRegionClosure {
HeapRegion* _a_region;
public:
FindFirstRegionClosure() : _a_region(NULL) {}
bool doHeapRegion(HeapRegion* r) {
_a_region = r;
return true;
}
HeapRegion* result() { return _a_region; }
};
void G1MarkSweep::mark_sweep_phase2() {
// Now all live objects are marked, compute the new object addresses.
// It is imperative that we traverse perm_gen LAST. If dead space is
// allowed a range of dead object may get overwritten by a dead int
// array. If perm_gen is not traversed last a klassOop may get
// overwritten. This is fine since it is dead, but if the class has dead
// instances we have to skip them, and in order to find their size we
// need the klassOop!
//
// It is not required that we traverse spaces in the same order in
// phase2, phase3 and phase4, but the ValidateMarkSweep live oops
// tracking expects us to do so. See comment under phase4.
G1CollectedHeap* g1h = G1CollectedHeap::heap();
Generation* pg = g1h->perm_gen();
EventMark m("2 compute new addresses");
TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
GenMarkSweep::trace("2");
FindFirstRegionClosure cl;
g1h->heap_region_iterate(&cl);
HeapRegion *r = cl.result();
CompactibleSpace* sp = r;
if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
sp = r->next_compaction_space();
}
G1PrepareCompactClosure blk(sp);
g1h->heap_region_iterate(&blk);
CompactPoint perm_cp(pg, NULL, NULL);
pg->prepare_for_compaction(&perm_cp);
}
class G1AdjustPointersClosure: public HeapRegionClosure {
public:
bool doHeapRegion(HeapRegion* r) {
if (r->isHumongous()) {
if (r->startsHumongous()) {
// We must adjust the pointers on the single H object.
oop obj = oop(r->bottom());
debug_only(GenMarkSweep::track_interior_pointers(obj));
// point all the oops to the new location
obj->adjust_pointers();
debug_only(GenMarkSweep::check_interior_pointers());
}
} else {
// This really ought to be "as_CompactibleSpace"...
r->adjust_pointers();
}
return false;
}
};
void G1MarkSweep::mark_sweep_phase3() {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
Generation* pg = g1h->perm_gen();
// Adjust the pointers to reflect the new locations
EventMark m("3 adjust pointers");
TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
GenMarkSweep::trace("3");
SharedHeap* sh = SharedHeap::heap();
sh->process_strong_roots(true, // activate StrongRootsScope
true, // Collecting permanent generation.
SharedHeap::SO_AllClasses,
&GenMarkSweep::adjust_root_pointer_closure,
NULL, // do not touch code cache here
&GenMarkSweep::adjust_pointer_closure);
g1h->ref_processor()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);
// Now adjust pointers in remaining weak roots. (All of which should
// have been cleared if they pointed to non-surviving objects.)
g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
&GenMarkSweep::adjust_pointer_closure);
GenMarkSweep::adjust_marks();
G1AdjustPointersClosure blk;
g1h->heap_region_iterate(&blk);
pg->adjust_pointers();
}
class G1SpaceCompactClosure: public HeapRegionClosure {
public:
G1SpaceCompactClosure() {}
bool doHeapRegion(HeapRegion* hr) {
if (hr->isHumongous()) {
if (hr->startsHumongous()) {
oop obj = oop(hr->bottom());
if (obj->is_gc_marked()) {
obj->init_mark();
} else {
assert(hr->is_empty(), "Should have been cleared in phase 2.");
}
hr->reset_during_compaction();
}
} else {
hr->compact();
}
return false;
}
};
void G1MarkSweep::mark_sweep_phase4() {
// All pointers are now adjusted, move objects accordingly
// It is imperative that we traverse perm_gen first in phase4. All
// classes must be allocated earlier than their instances, and traversing
// perm_gen first makes sure that all klassOops have moved to their new
// location before any instance does a dispatch through it's klass!
// The ValidateMarkSweep live oops tracking expects us to traverse spaces
// in the same order in phase2, phase3 and phase4. We don't quite do that
// here (perm_gen first rather than last), so we tell the validate code
// to use a higher index (saved from phase2) when verifying perm_gen.
G1CollectedHeap* g1h = G1CollectedHeap::heap();
Generation* pg = g1h->perm_gen();
EventMark m("4 compact heap");
TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
GenMarkSweep::trace("4");
pg->compact();
G1SpaceCompactClosure blk;
g1h->heap_region_iterate(&blk);
}
// Local Variables: ***
// c-indentation-style: gnu ***
// End: ***