8228720: Shenandoah: Implementation of concurrent class unloading
Reviewed-by: rkennke
/*
* Copyright (c) 2019, Red Hat, Inc. All rights reserved.
*
* 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "gc/shenandoah/shenandoahClosures.inline.hpp"
#include "gc/shenandoah/shenandoahConcurrentRoots.hpp"
#include "gc/shenandoah/shenandoahHeap.inline.hpp"
#include "gc/shenandoah/shenandoahNMethod.inline.hpp"
#include "memory/resourceArea.hpp"
ShenandoahNMethod::ShenandoahNMethod(nmethod* nm, GrowableArray<oop*>& oops, bool non_immediate_oops) :
_nm(nm), _oops(NULL), _oops_count(0), _unregistered(false) {
if (!oops.is_empty()) {
_oops_count = oops.length();
_oops = NEW_C_HEAP_ARRAY(oop*, _oops_count, mtGC);
for (int c = 0; c < _oops_count; c++) {
_oops[c] = oops.at(c);
}
}
_has_non_immed_oops = non_immediate_oops;
assert_same_oops();
}
ShenandoahNMethod::~ShenandoahNMethod() {
if (_oops != NULL) {
FREE_C_HEAP_ARRAY(oop*, _oops);
}
}
class ShenandoahHasCSetOopClosure : public OopClosure {
private:
ShenandoahHeap* const _heap;
bool _has_cset_oops;
public:
ShenandoahHasCSetOopClosure() :
_heap(ShenandoahHeap::heap()),
_has_cset_oops(false) {
}
bool has_cset_oops() const {
return _has_cset_oops;
}
void do_oop(oop* p) {
oop value = RawAccess<>::oop_load(p);
if (!_has_cset_oops && _heap->in_collection_set(value)) {
_has_cset_oops = true;
}
}
void do_oop(narrowOop* p) {
ShouldNotReachHere();
}
};
bool ShenandoahNMethod::has_cset_oops(ShenandoahHeap *heap) {
ShenandoahHasCSetOopClosure cl;
oops_do(&cl);
return cl.has_cset_oops();
}
void ShenandoahNMethod::update() {
ResourceMark rm;
bool non_immediate_oops = false;
GrowableArray<oop*> oops;
detect_reloc_oops(nm(), oops, non_immediate_oops);
if (oops.length() != _oops_count) {
if (_oops != NULL) {
FREE_C_HEAP_ARRAY(oop*, _oops);
_oops = NULL;
}
_oops_count = oops.length();
if (_oops_count > 0) {
_oops = NEW_C_HEAP_ARRAY(oop*, _oops_count, mtGC);
}
}
for (int index = 0; index < _oops_count; index ++) {
_oops[index] = oops.at(index);
}
_has_non_immed_oops = non_immediate_oops;
assert_same_oops();
}
void ShenandoahNMethod::oops_do(OopClosure* oops, bool fix_relocations) {
for (int c = 0; c < _oops_count; c ++) {
oops->do_oop(_oops[c]);
}
oop* const begin = _nm->oops_begin();
oop* const end = _nm->oops_end();
for (oop* p = begin; p < end; p++) {
if (*p != Universe::non_oop_word()) {
oops->do_oop(p);
}
}
if (fix_relocations && _has_non_immed_oops) {
_nm->fix_oop_relocations();
}
}
void ShenandoahNMethod::detect_reloc_oops(nmethod* nm, GrowableArray<oop*>& oops, bool& has_non_immed_oops) {
has_non_immed_oops = false;
// Find all oops relocations
RelocIterator iter(nm);
while (iter.next()) {
if (iter.type() != relocInfo::oop_type) {
// Not an oop
continue;
}
oop_Relocation* r = iter.oop_reloc();
if (!r->oop_is_immediate()) {
// Non-immediate oop found
has_non_immed_oops = true;
continue;
}
if (r->oop_value() != NULL) {
// Non-NULL immediate oop found. NULL oops can safely be
// ignored since the method will be re-registered if they
// are later patched to be non-NULL.
oops.push(r->oop_addr());
}
}
}
ShenandoahNMethod* ShenandoahNMethod::for_nmethod(nmethod* nm) {
ResourceMark rm;
bool non_immediate_oops = false;
GrowableArray<oop*> oops;
detect_reloc_oops(nm, oops, non_immediate_oops);
// No embedded oops
if(!ShenandoahConcurrentRoots::can_do_concurrent_class_unloading() &&
oops.is_empty() && nm->oops_begin() >= nm->oops_end()) {
return NULL;
}
return new ShenandoahNMethod(nm, oops, non_immediate_oops);
}
void ShenandoahNMethod::heal_nmethod(nmethod* nm) {
ShenandoahNMethod* data = gc_data(nm);
assert(data != NULL, "Sanity");
assert(data->lock()->owned_by_self(), "Must hold the lock");
ShenandoahEvacuateUpdateRootsClosure cl;
data->oops_do(&cl, true /*fix relocation*/);
}
#ifdef ASSERT
void ShenandoahNMethod::assert_alive_and_correct() {
assert(_nm->is_alive(), "only alive nmethods here");
ShenandoahHeap* heap = ShenandoahHeap::heap();
for (int c = 0; c < _oops_count; c++) {
oop *loc = _oops[c];
assert(_nm->code_contains((address) loc) || _nm->oops_contains(loc), "nmethod should contain the oop*");
oop o = RawAccess<>::oop_load(loc);
shenandoah_assert_correct_except(loc, o, o == NULL || heap->is_full_gc_move_in_progress());
}
oop* const begin = _nm->oops_begin();
oop* const end = _nm->oops_end();
for (oop* p = begin; p < end; p++) {
if (*p != Universe::non_oop_word()) {
oop o = RawAccess<>::oop_load(p);
shenandoah_assert_correct_except(p, o, o == NULL || heap->is_full_gc_move_in_progress());
}
}
}
class ShenandoahNMethodOopDetector : public OopClosure {
private:
ResourceMark rm; // For growable array allocation below.
GrowableArray<oop*> _oops;
public:
ShenandoahNMethodOopDetector() : _oops(10) {};
void do_oop(oop* o) {
_oops.append(o);
}
void do_oop(narrowOop* o) {
fatal("NMethods should not have compressed oops embedded.");
}
GrowableArray<oop*>* oops() {
return &_oops;
}
bool has_oops() {
return !_oops.is_empty();
}
};
void ShenandoahNMethod::assert_same_oops(bool allow_dead) {
ShenandoahNMethodOopDetector detector;
nm()->oops_do(&detector, allow_dead);
GrowableArray<oop*>* oops = detector.oops();
assert(oops->length() == oop_count(), "Must match");
for (int index = 0; index < _oops_count; index ++) {
assert(oops->contains(_oops[index]), "Must contain this oop");
}
for (oop* p = nm()->oops_begin(); p < nm()->oops_end(); p ++) {
assert(oops->contains(p), "Must contain this oop");
}
}
void ShenandoahNMethod::assert_no_oops(nmethod* nm, bool allow_dead) {
ShenandoahNMethodOopDetector detector;
nm->oops_do(&detector, allow_dead);
assert(detector.oops()->length() == 0, "Should not have oops");
}
#endif
ShenandoahNMethodTable::ShenandoahNMethodTable() :
_heap(ShenandoahHeap::heap()),
_size(minSize),
_index(0),
_iteration_in_progress(false) {
_array = NEW_C_HEAP_ARRAY(ShenandoahNMethod*, _size, mtGC);
}
ShenandoahNMethodTable::~ShenandoahNMethodTable() {
assert(_array != NULL, "Sanity");
FREE_C_HEAP_ARRAY(ShenandoahNMethod*, _array);
}
void ShenandoahNMethodTable::register_nmethod(nmethod* nm) {
assert(CodeCache_lock->owned_by_self(), "Must have CodeCache_lock held");
assert(_index >= 0 && _index <= _size, "Sanity");
ShenandoahNMethod* data = ShenandoahNMethod::gc_data(nm);
ShenandoahReentrantLocker data_locker(data != NULL ? data->lock() : NULL);
if (data != NULL) {
assert(contain(nm), "Must have been registered");
data->update();
} else {
data = ShenandoahNMethod::for_nmethod(nm);
if (data == NULL) {
assert(!ShenandoahConcurrentRoots::can_do_concurrent_class_unloading(),
"Only possible when concurrent class unloading is off");
return;
}
ShenandoahNMethod::attach_gc_data(nm, data);
ShenandoahLocker locker(&_lock);
log_register_nmethod(nm);
append(data);
}
// Disarm new nmethod
ShenandoahNMethod::disarm_nmethod(nm);
}
void ShenandoahNMethodTable::unregister_nmethod(nmethod* nm) {
assert_locked_or_safepoint(CodeCache_lock);
ShenandoahNMethod* data = ShenandoahNMethod::gc_data(nm);
if (data == NULL) {
assert(!ShenandoahConcurrentRoots::can_do_concurrent_class_unloading(),
"Only possible when concurrent class unloading is off");
ShenandoahNMethod::assert_no_oops(nm, true /*allow_dead*/);
return;
}
if (Thread::current()->is_Code_cache_sweeper_thread()) {
wait_until_concurrent_iteration_done();
}
log_unregister_nmethod(nm);
ShenandoahLocker locker(&_lock);
assert(contain(nm), "Must have been registered");
ShenandoahReentrantLocker data_locker(data->lock());
data->mark_unregistered();
}
void ShenandoahNMethodTable::flush_nmethod(nmethod* nm) {
assert(CodeCache_lock->owned_by_self(), "Must have CodeCache_lock held");
assert(Thread::current()->is_Code_cache_sweeper_thread(), "Must from Sweep thread");
ShenandoahNMethod* data = ShenandoahNMethod::gc_data(nm);
assert(data != NULL || !ShenandoahConcurrentRoots::can_do_concurrent_class_unloading(),
"Only possible when concurrent class unloading is off");
if (data == NULL) {
ShenandoahNMethod::assert_no_oops(nm, true /*allow_dead*/);
return;
}
// Can not alter the array when iteration is in progress
wait_until_concurrent_iteration_done();
log_flush_nmethod(nm);
ShenandoahLocker locker(&_lock);
int idx = index_of(nm);
assert(idx >= 0 && idx < _index, "Invalid index");
ShenandoahNMethod::attach_gc_data(nm, NULL);
remove(idx);
}
bool ShenandoahNMethodTable::contain(nmethod* nm) const {
return index_of(nm) != -1;
}
ShenandoahNMethod* ShenandoahNMethodTable::at(int index) const {
assert(index >= 0 && index < _index, "Out of bound");
return _array[index];
}
int ShenandoahNMethodTable::index_of(nmethod* nm) const {
for (int index = 0; index < length(); index ++) {
if (_array[index]->nm() == nm) {
return index;
}
}
return -1;
}
void ShenandoahNMethodTable::remove(int idx) {
shenandoah_assert_locked_or_safepoint(CodeCache_lock);
assert(!_iteration_in_progress, "Can not happen");
assert(_index >= 0 && _index <= _size, "Sanity");
assert(idx >= 0 && idx < _index, "Out of bound");
ShenandoahNMethod* snm = _array[idx];
_index --;
_array[idx] = _array[_index];
delete snm;
}
void ShenandoahNMethodTable::wait_until_concurrent_iteration_done() {
assert(CodeCache_lock->owned_by_self(), "Lock must be held");
while (iteration_in_progress()) {
CodeCache_lock->wait_without_safepoint_check();
}
}
void ShenandoahNMethodTable::append(ShenandoahNMethod* snm) {
if (is_full()) {
int new_size = 2 * _size;
ShenandoahNMethod** old_table = _array;
// Rebuild table and replace current one
rebuild(new_size);
// An iteration is in progress over early snapshot,
// can not release the array until iteration is completed
if (!iteration_in_progress()) {
FREE_C_HEAP_ARRAY(ShenandoahNMethod*, old_table);
}
}
_array[_index ++] = snm;
assert(_index >= 0 && _index <= _size, "Sanity");
}
void ShenandoahNMethodTable::rebuild(int size) {
ShenandoahNMethod** arr = NEW_C_HEAP_ARRAY(ShenandoahNMethod*, size, mtGC);
for (int index = 0; index < _index; index ++) {
arr[index] = _array[index];
}
_array = arr;
_size = size;
}
ShenandoahNMethodTableSnapshot* ShenandoahNMethodTable::snapshot_for_iteration() {
assert(!iteration_in_progress(), "Already in progress");
_iteration_in_progress = true;
return new ShenandoahNMethodTableSnapshot(this);
}
void ShenandoahNMethodTable::finish_iteration(ShenandoahNMethodTableSnapshot* snapshot) {
assert(iteration_in_progress(), "Why we here?");
assert(snapshot != NULL, "No snapshot");
_iteration_in_progress = false;
// Table has been rebuilt during iteration, free old table
if (snapshot->_array != _array) {
FREE_C_HEAP_ARRAY(ShenandoahNMethod*, snapshot->_array);
}
delete snapshot;
}
void ShenandoahNMethodTable::log_register_nmethod(nmethod* nm) {
LogTarget(Debug, gc, nmethod) log;
if (!log.is_enabled()) {
return;
}
ResourceMark rm;
log.print("Register NMethod: %s.%s [" PTR_FORMAT "] (%s)",
nm->method()->method_holder()->external_name(),
nm->method()->name()->as_C_string(),
p2i(nm),
nm->compiler_name());
}
void ShenandoahNMethodTable::log_unregister_nmethod(nmethod* nm) {
LogTarget(Debug, gc, nmethod) log;
if (!log.is_enabled()) {
return;
}
ResourceMark rm;
log.print("Unregister NMethod: %s.%s [" PTR_FORMAT "]",
nm->method()->method_holder()->external_name(),
nm->method()->name()->as_C_string(),
p2i(nm));
}
void ShenandoahNMethodTable::log_flush_nmethod(nmethod* nm) {
LogTarget(Debug, gc, nmethod) log;
if (!log.is_enabled()) {
return;
}
ResourceMark rm;
log.print("Flush NMethod: (" PTR_FORMAT ")", p2i(nm));
}
#ifdef ASSERT
void ShenandoahNMethodTable::assert_nmethods_alive_and_correct() {
assert_locked_or_safepoint(CodeCache_lock);
for (int index = 0; index < length(); index ++) {
ShenandoahNMethod* m = _array[index];
// Concurrent unloading may have dead nmethods to be cleaned by sweeper
if (m->is_unregistered()) continue;
m->assert_alive_and_correct();
}
}
#endif
ShenandoahNMethodTableSnapshot::ShenandoahNMethodTableSnapshot(ShenandoahNMethodTable* table) :
_heap(ShenandoahHeap::heap()), _table(table), _array(table->_array), _length(table->_index), _claimed(0) {
}
void ShenandoahNMethodTableSnapshot::concurrent_nmethods_do(NMethodClosure* cl) {
size_t stride = 256; // educated guess
ShenandoahNMethod** list = _array;
size_t max = (size_t)_length;
while (_claimed < max) {
size_t cur = Atomic::add(&_claimed, stride) - stride;
size_t start = cur;
size_t end = MIN2(cur + stride, max);
if (start >= max) break;
for (size_t idx = start; idx < end; idx++) {
ShenandoahNMethod* data = list[idx];
assert(data != NULL, "Should not be NULL");
if (!data->is_unregistered()) {
cl->do_nmethod(data->nm());
}
}
}
}
ShenandoahConcurrentNMethodIterator::ShenandoahConcurrentNMethodIterator(ShenandoahNMethodTable* table) :
_table(table), _table_snapshot(NULL) {
}
void ShenandoahConcurrentNMethodIterator::nmethods_do_begin() {
assert(CodeCache_lock->owned_by_self(), "Lock must be held");
assert(ShenandoahConcurrentRoots::can_do_concurrent_class_unloading(),
"Only for concurrent class unloading");
_table_snapshot = _table->snapshot_for_iteration();
}
void ShenandoahConcurrentNMethodIterator::nmethods_do(NMethodClosure* cl) {
assert(_table_snapshot != NULL, "Must first call nmethod_do_begin()");
_table_snapshot->concurrent_nmethods_do(cl);
}
void ShenandoahConcurrentNMethodIterator::nmethods_do_end() {
assert(CodeCache_lock->owned_by_self(), "Lock must be held");
assert(ShenandoahConcurrentRoots::can_do_concurrent_class_unloading(),
"Only for concurrent class unloading");
_table->finish_iteration(_table_snapshot);
CodeCache_lock->notify_all();
}