void G1AllocRegion::retire(bool fill_up) {
assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));
trace("retiring");
HeapRegion* alloc_region = _alloc_region;
if (alloc_region != _dummy_region) {
// We never have to check whether the active region is empty or not,
// and potentially free it if it is, given that it's guaranteed that
// it will never be empty.
assert(!alloc_region->is_empty(),
ar_ext_msg(this, "the alloc region should never be empty"));
if (fill_up) {
fill_up_remaining_space(alloc_region, _bot_updates);
}
assert(alloc_region->used() >= _used_bytes_before,
ar_ext_msg(this, "invariant"));
size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
retire_region(alloc_region, allocated_bytes);
_used_bytes_before = 0;
_alloc_region = _dummy_region;
}
trace("retired");
}
HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
bool force) {
assert(_alloc_region == _dummy_region, ar_ext_msg(this, "pre-condition"));
assert(_used_bytes_before == 0, ar_ext_msg(this, "pre-condition"));
trace("attempting region allocation");
HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
if (new_alloc_region != NULL) {
new_alloc_region->reset_pre_dummy_top();
// Need to do this before the allocation
_used_bytes_before = new_alloc_region->used();
HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
assert(result != NULL, ar_ext_msg(this, "the allocation should succeeded"));
OrderAccess::storestore();
// Note that we first perform the allocation and then we store the
// region in _alloc_region. This is the reason why an active region
// can never be empty.
_alloc_region = new_alloc_region;
_count += 1;
trace("region allocation successful");
return result;
} else {
trace("region allocation failed");
return NULL;
}
ShouldNotReachHere();
}
void G1AllocRegion::init() {
trace("initializing");
assert(_alloc_region == NULL && _used_bytes_before == 0,
ar_ext_msg(this, "pre-condition"));
assert(_dummy_region != NULL, ar_ext_msg(this, "should have been set"));
_alloc_region = _dummy_region;
_count = 0;
trace("initialized");
}
inline HeapWord* G1AllocRegion::attempt_allocation_force(size_t word_size,
bool bot_updates) {
assert(bot_updates == _bot_updates, ar_ext_msg(this, "pre-condition"));
assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));
trace("forcing alloc");
HeapWord* result = new_alloc_region_and_allocate(word_size, true /* force */);
if (result != NULL) {
trace("alloc forced", word_size, result);
return result;
}
trace("alloc forced failed", word_size);
return NULL;
}
void G1AllocRegion::set(HeapRegion* alloc_region) {
trace("setting");
// We explicitly check that the region is not empty to make sure we
// maintain the "the alloc region cannot be empty" invariant.
assert(alloc_region != NULL && !alloc_region->is_empty(),
ar_ext_msg(this, "pre-condition"));
assert(_alloc_region == _dummy_region &&
_used_bytes_before == 0 && _count == 0,
ar_ext_msg(this, "pre-condition"));
_used_bytes_before = alloc_region->used();
_alloc_region = alloc_region;
_count += 1;
trace("set");
}
/**
* 并发分配
*/
inline HeapWord* G1AllocRegion::attempt_allocation(size_t word_size,
bool bot_updates) {
assert(bot_updates == _bot_updates, ar_ext_msg(this, "pre-condition"));
HeapRegion* alloc_region = _alloc_region;
assert(alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));
HeapWord* result = par_allocate(alloc_region, word_size, bot_updates);
if (result != NULL) {
trace("alloc", word_size, result);
return result;
}
trace("alloc failed", word_size);
return NULL;
}
HeapRegion* G1AllocRegion::release() {
trace("releasing");
HeapRegion* alloc_region = _alloc_region;
retire(false /* fill_up */);
assert(_alloc_region == _dummy_region,
ar_ext_msg(this, "post-condition of retire()"));
_alloc_region = NULL;
trace("released");
return (alloc_region == _dummy_region) ? NULL : alloc_region;
}
void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
trace("update");
// We explicitly check that the region is not empty to make sure we
// maintain the "the alloc region cannot be empty" invariant.
assert(alloc_region != NULL && !alloc_region->is_empty(),
ar_ext_msg(this, "pre-condition"));
_alloc_region = alloc_region;
_alloc_region->set_allocation_context(allocation_context());
_count += 1;
trace("updated");
}