DefNewGeneration::DefNewGeneration(ReservedSpace rs,
size_t initial_size,
const char* policy)
: Generation(rs, initial_size),
_promo_failure_drain_in_progress(false),
_should_allocate_from_space(false)
{
MemRegion cmr((HeapWord*)_virtual_space.low(),
(HeapWord*)_virtual_space.high());
GenCollectedHeap* gch = GenCollectedHeap::heap();
gch->barrier_set()->resize_covered_region(cmr);
_eden_space = new ContiguousSpace();
_from_space = new ContiguousSpace();
_to_space = new ContiguousSpace();
if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
vm_exit_during_initialization("Could not allocate a new gen space");
}
// Compute the maximum eden and survivor space sizes. These sizes
// are computed assuming the entire reserved space is committed.
// These values are exported as performance counters.
uintx alignment = gch->collector_policy()->space_alignment();
uintx size = _virtual_space.reserved_size();
_max_survivor_size = compute_survivor_size(size, alignment);
_max_eden_size = size - (2*_max_survivor_size);
// allocate the performance counters
GenCollectorPolicy* gcp = gch->gen_policy();
// Generation counters -- generation 0, 3 subspaces
_gen_counters = new GenerationCounters("new", 0, 3,
gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
_gc_counters = new CollectorCounters(policy, 0);
_eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
_gen_counters);
_from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
_gen_counters);
_to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
_gen_counters);
compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
update_counters();
_old_gen = NULL;
_tenuring_threshold = MaxTenuringThreshold;
_pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
_gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
}
void DefNewGeneration::compute_new_size() {
// This is called after a GC that includes the old generation, so from-space
// will normally be empty.
// Note that we check both spaces, since if scavenge failed they revert roles.
// If not we bail out (otherwise we would have to relocate the objects).
if (!from()->is_empty() || !to()->is_empty()) {
return;
}
GenCollectedHeap* gch = GenCollectedHeap::heap();
size_t old_size = gch->old_gen()->capacity();
size_t new_size_before = _virtual_space.committed_size();
size_t min_new_size = initial_size();
size_t max_new_size = reserved().byte_size();
assert(min_new_size <= new_size_before &&
new_size_before <= max_new_size,
"just checking");
// All space sizes must be multiples of Generation::GenGrain.
size_t alignment = Generation::GenGrain;
// Compute desired new generation size based on NewRatio and
// NewSizeThreadIncrease
size_t desired_new_size = old_size/NewRatio;
int threads_count = Threads::number_of_non_daemon_threads();
size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
// Adjust new generation size
desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
assert(desired_new_size <= max_new_size, "just checking");
bool changed = false;
if (desired_new_size > new_size_before) {
size_t change = desired_new_size - new_size_before;
assert(change % alignment == 0, "just checking");
if (expand(change)) {
changed = true;
}
// If the heap failed to expand to the desired size,
// "changed" will be false. If the expansion failed
// (and at this point it was expected to succeed),
// ignore the failure (leaving "changed" as false).
}
if (desired_new_size < new_size_before && eden()->is_empty()) {
// bail out of shrinking if objects in eden
size_t change = new_size_before - desired_new_size;
assert(change % alignment == 0, "just checking");
_virtual_space.shrink_by(change);
changed = true;
}
if (changed) {
// The spaces have already been mangled at this point but
// may not have been cleared (set top = bottom) and should be.
// Mangling was done when the heap was being expanded.
compute_space_boundaries(eden()->used(),
SpaceDecorator::Clear,
SpaceDecorator::DontMangle);
MemRegion cmr((HeapWord*)_virtual_space.low(),
(HeapWord*)_virtual_space.high());
gch->barrier_set()->resize_covered_region(cmr);
log_debug(gc, heap, ergo)(
"New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
new_size_before/K, _virtual_space.committed_size()/K,
eden()->capacity()/K, from()->capacity()/K);
log_trace(gc, heap, ergo)(
" [allowed " SIZE_FORMAT "K extra for %d threads]",
thread_increase_size/K, threads_count);
}
}