提交 1a26624c 编写于 作者: J jcoomes

6765954: par compact - stress mode for splitting young gen spaces

Reviewed-by: jmasa
上级 ca1cddf2
......@@ -1327,6 +1327,13 @@ HeapWord*
PSParallelCompact::compute_dense_prefix(const SpaceId id,
bool maximum_compaction)
{
if (ParallelOldGCSplitALot) {
if (_space_info[id].dense_prefix() != _space_info[id].space()->bottom()) {
// The value was chosen to provoke splitting a young gen space; use it.
return _space_info[id].dense_prefix();
}
}
const size_t region_size = ParallelCompactData::RegionSize;
const ParallelCompactData& sd = summary_data();
......@@ -1415,6 +1422,160 @@ PSParallelCompact::compute_dense_prefix(const SpaceId id,
return sd.region_to_addr(best_cp);
}
#ifndef PRODUCT
void
PSParallelCompact::fill_with_live_objects(SpaceId id, HeapWord* const start,
size_t words)
{
if (TraceParallelOldGCSummaryPhase) {
tty->print_cr("fill_with_live_objects [" PTR_FORMAT " " PTR_FORMAT ") "
SIZE_FORMAT, start, start + words, words);
}
ObjectStartArray* const start_array = _space_info[id].start_array();
CollectedHeap::fill_with_objects(start, words);
for (HeapWord* p = start; p < start + words; p += oop(p)->size()) {
_mark_bitmap.mark_obj(p, words);
_summary_data.add_obj(p, words);
start_array->allocate_block(p);
}
}
void
PSParallelCompact::summarize_new_objects(SpaceId id, HeapWord* start)
{
ParallelCompactData& sd = summary_data();
MutableSpace* space = _space_info[id].space();
// Find the source and destination start addresses.
HeapWord* const src_addr = sd.region_align_down(start);
HeapWord* dst_addr;
if (src_addr < start) {
dst_addr = sd.addr_to_region_ptr(src_addr)->destination();
} else if (src_addr > space->bottom()) {
// The start (the original top() value) is aligned to a region boundary so
// the associated region does not have a destination. Compute the
// destination from the previous region.
RegionData* const cp = sd.addr_to_region_ptr(src_addr) - 1;
dst_addr = cp->destination() + cp->data_size();
} else {
// Filling the entire space.
dst_addr = space->bottom();
}
assert(dst_addr != NULL, "sanity");
// Update the summary data.
bool result = _summary_data.summarize(_space_info[id].split_info(),
src_addr, space->top(), NULL,
dst_addr, space->end(),
_space_info[id].new_top_addr());
assert(result, "should not fail: bad filler object size");
}
void
PSParallelCompact::provoke_split(bool & max_compaction)
{
const size_t region_size = ParallelCompactData::RegionSize;
ParallelCompactData& sd = summary_data();
MutableSpace* const eden_space = _space_info[eden_space_id].space();
MutableSpace* const from_space = _space_info[from_space_id].space();
const size_t eden_live = pointer_delta(eden_space->top(),
_space_info[eden_space_id].new_top());
const size_t from_live = pointer_delta(from_space->top(),
_space_info[from_space_id].new_top());
const size_t min_fill_size = CollectedHeap::min_fill_size();
const size_t eden_free = pointer_delta(eden_space->end(), eden_space->top());
const size_t eden_fillable = eden_free >= min_fill_size ? eden_free : 0;
const size_t from_free = pointer_delta(from_space->end(), from_space->top());
const size_t from_fillable = from_free >= min_fill_size ? from_free : 0;
// Choose the space to split; need at least 2 regions live (or fillable).
SpaceId id;
MutableSpace* space;
size_t live_words;
size_t fill_words;
if (eden_live + eden_fillable >= region_size * 2) {
id = eden_space_id;
space = eden_space;
live_words = eden_live;
fill_words = eden_fillable;
} else if (from_live + from_fillable >= region_size * 2) {
id = from_space_id;
space = from_space;
live_words = from_live;
fill_words = from_fillable;
} else {
return; // Give up.
}
assert(fill_words == 0 || fill_words >= min_fill_size, "sanity");
if (live_words < region_size * 2) {
// Fill from top() to end() w/live objects of mixed sizes.
HeapWord* const fill_start = space->top();
live_words += fill_words;
space->set_top(fill_start + fill_words);
if (ZapUnusedHeapArea) {
space->set_top_for_allocations();
}
HeapWord* cur_addr = fill_start;
while (fill_words > 0) {
const size_t r = (size_t)os::random() % (region_size / 2) + min_fill_size;
size_t cur_size = MIN2(align_object_size_(r), fill_words);
if (fill_words - cur_size < min_fill_size) {
cur_size = fill_words; // Avoid leaving a fragment too small to fill.
}
CollectedHeap::fill_with_object(cur_addr, cur_size);
mark_bitmap()->mark_obj(cur_addr, cur_size);
sd.add_obj(cur_addr, cur_size);
cur_addr += cur_size;
fill_words -= cur_size;
}
summarize_new_objects(id, fill_start);
}
max_compaction = false;
// Manipulate the old gen so that it has room for about half of the live data
// in the target young gen space (live_words / 2).
id = old_space_id;
space = _space_info[id].space();
const size_t free_at_end = space->free_in_words();
const size_t free_target = align_object_size(live_words / 2);
const size_t dead = pointer_delta(space->top(), _space_info[id].new_top());
if (free_at_end >= free_target + min_fill_size) {
// Fill space above top() and set the dense prefix so everything survives.
HeapWord* const fill_start = space->top();
const size_t fill_size = free_at_end - free_target;
space->set_top(space->top() + fill_size);
if (ZapUnusedHeapArea) {
space->set_top_for_allocations();
}
fill_with_live_objects(id, fill_start, fill_size);
summarize_new_objects(id, fill_start);
_space_info[id].set_dense_prefix(sd.region_align_down(space->top()));
} else if (dead + free_at_end > free_target) {
// Find a dense prefix that makes the right amount of space available.
HeapWord* cur = sd.region_align_down(space->top());
HeapWord* cur_destination = sd.addr_to_region_ptr(cur)->destination();
size_t dead_to_right = pointer_delta(space->end(), cur_destination);
while (dead_to_right < free_target) {
cur -= region_size;
cur_destination = sd.addr_to_region_ptr(cur)->destination();
dead_to_right = pointer_delta(space->end(), cur_destination);
}
_space_info[id].set_dense_prefix(cur);
}
}
#endif // #ifndef PRODUCT
void PSParallelCompact::summarize_spaces_quick()
{
for (unsigned int i = 0; i < last_space_id; ++i) {
......@@ -1508,8 +1669,9 @@ void
PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
{
assert(id < last_space_id, "id out of range");
assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom(),
"should have been set in summarize_spaces_quick()");
assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom() ||
ParallelOldGCSplitALot && id == old_space_id,
"should have been reset in summarize_spaces_quick()");
const MutableSpace* space = _space_info[id].space();
if (_space_info[id].new_top() != space->bottom()) {
......@@ -1525,15 +1687,15 @@ PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
}
#endif // #ifndef PRODUCT
// Recompute the summary data, taking into account the dense prefix. If every
// last byte will be reclaimed, then the existing summary data which compacts
// everything can be left in place.
// Recompute the summary data, taking into account the dense prefix. If
// every last byte will be reclaimed, then the existing summary data which
// compacts everything can be left in place.
if (!maximum_compaction && dense_prefix_end != space->bottom()) {
// If dead space crosses the dense prefix boundary, it is (at least
// partially) filled with a dummy object, marked live and added to the
// summary data. This simplifies the copy/update phase and must be done
// before the final locations of objects are determined, to prevent leaving
// a fragment of dead space that is too small to fill with an object.
// before the final locations of objects are determined, to prevent
// leaving a fragment of dead space that is too small to fill.
fill_dense_prefix_end(id);
// Compute the destination of each Region, and thus each object.
......@@ -1625,10 +1787,18 @@ void PSParallelCompact::summary_phase(ParCompactionManager* cm,
}
MutableSpace* const old_space = _space_info[old_space_id].space();
if (old_space_total_live > old_space->capacity_in_words()) {
const size_t old_capacity = old_space->capacity_in_words();
if (old_space_total_live > old_capacity) {
// XXX - should also try to expand
maximum_compaction = true;
}
#ifndef PRODUCT
if (ParallelOldGCSplitALot && old_space_total_live < old_capacity) {
if (total_invocations() % ParallelOldGCSplitInterval == 0) {
provoke_split(maximum_compaction);
}
}
#endif // #ifndef PRODUCT
// Permanent and Old generations.
summarize_space(perm_space_id, maximum_compaction);
......
......@@ -968,6 +968,20 @@ class PSParallelCompact : AllStatic {
// Clear the summary data source_region field for the specified addresses.
static void clear_source_region(HeapWord* beg_addr, HeapWord* end_addr);
#ifndef PRODUCT
// Routines to provoke splitting a young gen space (ParallelOldGCSplitALot).
// Fill the region [start, start + words) with live object(s). Only usable
// for the old and permanent generations.
static void fill_with_live_objects(SpaceId id, HeapWord* const start,
size_t words);
// Include the new objects in the summary data.
static void summarize_new_objects(SpaceId id, HeapWord* start);
// Add live objects and/or choose the dense prefix to provoke splitting.
static void provoke_split(bool & maximum_compaction);
#endif
static void summarize_spaces_quick();
static void summarize_space(SpaceId id, bool maximum_compaction);
static void summary_phase(ParCompactionManager* cm, bool maximum_compaction);
......
......@@ -1517,6 +1517,16 @@ bool Arguments::check_vm_args_consistency() {
MarkSweepAlwaysCompactCount = 1; // Move objects every gc.
}
if (UseParallelOldGC && ParallelOldGCSplitALot) {
// Settings to encourage splitting.
if (!FLAG_IS_CMDLINE(NewRatio)) {
FLAG_SET_CMDLINE(intx, NewRatio, 2);
}
if (!FLAG_IS_CMDLINE(ScavengeBeforeFullGC)) {
FLAG_SET_CMDLINE(bool, ScavengeBeforeFullGC, false);
}
}
status = status && verify_percentage(GCHeapFreeLimit, "GCHeapFreeLimit");
status = status && verify_percentage(GCTimeLimit, "GCTimeLimit");
if (GCTimeLimit == 100) {
......
......@@ -1203,11 +1203,12 @@ class CommandLineFlags {
product(uintx, ParallelCMSThreads, 0, \
"Max number of threads CMS will use for concurrent work") \
\
develop(bool, ParallelOldMTUnsafeMarkBitMap, false, \
"Use the Parallel Old MT unsafe in marking the bitmap") \
develop(bool, ParallelOldGCSplitALot, false, \
"Provoke splitting (copying data from a young gen space to" \
"multiple destination spaces)") \
\
develop(bool, ParallelOldMTUnsafeUpdateLiveData, false, \
"Use the Parallel Old MT unsafe in update of live size") \
develop(uintx, ParallelOldGCSplitInterval, 3, \
"How often to provoke splitting a young gen space") \
\
develop(bool, TraceRegionTasksQueuing, false, \
"Trace the queuing of the region tasks") \
......
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