void VM_GenCollectForPermanentAllocation::doit() {
SvcGCMarker sgcm(SvcGCMarker::FULL);
SharedHeap* heap = (SharedHeap*)Universe::heap();
GCCauseSetter gccs(heap, _gc_cause);
switch (heap->kind()) {
case (CollectedHeap::GenCollectedHeap): {
GenCollectedHeap* gch = (GenCollectedHeap*)heap;
gch->do_full_collection(gch->must_clear_all_soft_refs(),
gch->n_gens() - 1);
break;
}
#ifndef SERIALGC
case (CollectedHeap::G1CollectedHeap): {
G1CollectedHeap* g1h = (G1CollectedHeap*)heap;
g1h->do_full_collection(_gc_cause == GCCause::_last_ditch_collection);
break;
}
#endif // SERIALGC
default:
ShouldNotReachHere();
}
_res = heap->perm_gen()->allocate(_size, false);
assert(heap->is_in_reserved_or_null(_res), "result not in heap");
if (_res == NULL && GC_locker::is_active_and_needs_gc()) {
set_gc_locked();
}
}
/**
* 标记清除的方式回收内存堆的垃圾对象
* 1.第一步: 标记所有存活的对象
* 2.第二步: 计算存活的对象在其内存区压缩后的偏移位置
* 3.第三步: 遍历所有存活的对象并修改其对应的地址映射表
* 4.第四步: 移动存活的对象压缩内存区
*/
void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp,
bool clear_all_softrefs) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
GenCollectedHeap* gch = GenCollectedHeap::heap();
#ifdef ASSERT
if (gch->collector_policy()->should_clear_all_soft_refs()) {
assert(clear_all_softrefs, "Policy should have been checked earlier");
}
#endif
// hook up weak ref data so it can be used during Mark-Sweep
assert(ref_processor() == NULL, "no stomping");
assert(rp != NULL, "should be non-NULL");
_ref_processor = rp;
rp->setup_policy(clear_all_softrefs);
TraceTime t1("Full GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
// 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.
gch->perm_gen()->stat_record()->invocations++;
//本次Gc之前内存堆的使用量
size_t gch_prev_used = gch->used();
// Some of the card table updates below assume that the perm gen is
// also being collected.
assert(level == gch->n_gens() - 1, "All generations are being collected, ergo perm gen too.");
// Capture used regions for each generation that will be
// subject to collection, so that card table adjustments can
// be made intelligently (see clear / invalidate further below).
gch->save_used_regions(level, true /* perm */);
allocate_stacks();
mark_sweep_phase1(level, clear_all_softrefs);
mark_sweep_phase2();
// Don't add any more derived pointers during phase3
COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
mark_sweep_phase3(level);
VALIDATE_MARK_SWEEP_ONLY(
if (ValidateMarkSweep) {
guarantee(_root_refs_stack->length() == 0, "should be empty by now");
}
)
jbyte CardTableRS::find_unused_youngergenP_card_value() {
GenCollectedHeap* gch = GenCollectedHeap::heap();
for (jbyte v = youngergenP1_card;
v < cur_youngergen_and_prev_nonclean_card;
v++) {
bool seen = false;
for (int g = 0; g < gch->n_gens()+1; g++) {
if (_last_cur_val_in_gen[g] == v) {
seen = true;
break;
}
}
if (!seen) return v;
}
ShouldNotReachHere();
return 0;
}