--- a/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp Thu Jan 12 00:06:47 2012 -0800
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp Wed Jan 25 12:58:23 2012 -0500
@@ -460,6 +460,84 @@
&& !nextMarkBitMap()->isMarked((HeapWord*)obj)));
}
+CMRootRegions::CMRootRegions() :
+ _young_list(NULL), _cm(NULL), _scan_in_progress(false),
+ _should_abort(false), _next_survivor(NULL) { }
+
+void CMRootRegions::init(G1CollectedHeap* g1h, ConcurrentMark* cm) {
+ _young_list = g1h->young_list();
+ _cm = cm;
+}
+
+void CMRootRegions::prepare_for_scan() {
+ assert(!scan_in_progress(), "pre-condition");
+
+ // Currently, only survivors can be root regions.
+ assert(_next_survivor == NULL, "pre-condition");
+ _next_survivor = _young_list->first_survivor_region();
+ _scan_in_progress = (_next_survivor != NULL);
+ _should_abort = false;
+}
+
+HeapRegion* CMRootRegions::claim_next() {
+ if (_should_abort) {
+ // If someone has set the should_abort flag, we return NULL to
+ // force the caller to bail out of their loop.
+ return NULL;
+ }
+
+ // Currently, only survivors can be root regions.
+ HeapRegion* res = _next_survivor;
+ if (res != NULL) {
+ MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
+ // Read it again in case it changed while we were waiting for the lock.
+ res = _next_survivor;
+ if (res != NULL) {
+ if (res == _young_list->last_survivor_region()) {
+ // We just claimed the last survivor so store NULL to indicate
+ // that we're done.
+ _next_survivor = NULL;
+ } else {
+ _next_survivor = res->get_next_young_region();
+ }
+ } else {
+ // Someone else claimed the last survivor while we were trying
+ // to take the lock so nothing else to do.
+ }
+ }
+ assert(res == NULL || res->is_survivor(), "post-condition");
+
+ return res;
+}
+
+void CMRootRegions::scan_finished() {
+ assert(scan_in_progress(), "pre-condition");
+
+ // Currently, only survivors can be root regions.
+ if (!_should_abort) {
+ assert(_next_survivor == NULL, "we should have claimed all survivors");
+ }
+ _next_survivor = NULL;
+
+ {
+ MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
+ _scan_in_progress = false;
+ RootRegionScan_lock->notify_all();
+ }
+}
+
+bool CMRootRegions::wait_until_scan_finished() {
+ if (!scan_in_progress()) return false;
+
+ {
+ MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
+ while (scan_in_progress()) {
+ RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
+ }
+ }
+ return true;
+}
+
#ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
#pragma warning( disable:4355 ) // 'this' : used in base member initializer list
#endif // _MSC_VER
@@ -548,6 +626,8 @@
SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
satb_qs.set_buffer_size(G1SATBBufferSize);
+ _root_regions.init(_g1h, this);
+
_tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_task_num);
_accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_task_num);
@@ -864,6 +944,8 @@
satb_mq_set.set_active_all_threads(true, /* new active value */
false /* expected_active */);
+ _root_regions.prepare_for_scan();
+
// update_g1_committed() will be called at the end of an evac pause
// when marking is on. So, it's also called at the end of the
// initial-mark pause to update the heap end, if the heap expands
@@ -1157,6 +1239,69 @@
return 0;
}
+void ConcurrentMark::scanRootRegion(HeapRegion* hr, uint worker_id) {
+ // Currently, only survivors can be root regions.
+ assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
+ G1RootRegionScanClosure cl(_g1h, this, worker_id);
+
+ const uintx interval = PrefetchScanIntervalInBytes;
+ HeapWord* curr = hr->bottom();
+ const HeapWord* end = hr->top();
+ while (curr < end) {
+ Prefetch::read(curr, interval);
+ oop obj = oop(curr);
+ int size = obj->oop_iterate(&cl);
+ assert(size == obj->size(), "sanity");
+ curr += size;
+ }
+}
+
+class CMRootRegionScanTask : public AbstractGangTask {
+private:
+ ConcurrentMark* _cm;
+
+public:
+ CMRootRegionScanTask(ConcurrentMark* cm) :
+ AbstractGangTask("Root Region Scan"), _cm(cm) { }
+
+ void work(uint worker_id) {
+ assert(Thread::current()->is_ConcurrentGC_thread(),
+ "this should only be done by a conc GC thread");
+
+ CMRootRegions* root_regions = _cm->root_regions();
+ HeapRegion* hr = root_regions->claim_next();
+ while (hr != NULL) {
+ _cm->scanRootRegion(hr, worker_id);
+ hr = root_regions->claim_next();
+ }
+ }
+};
+
+void ConcurrentMark::scanRootRegions() {
+ // scan_in_progress() will have been set to true only if there was
+ // at least one root region to scan. So, if it's false, we
+ // should not attempt to do any further work.
+ if (root_regions()->scan_in_progress()) {
+ _parallel_marking_threads = calc_parallel_marking_threads();
+ assert(parallel_marking_threads() <= max_parallel_marking_threads(),
+ "Maximum number of marking threads exceeded");
+ uint active_workers = MAX2(1U, parallel_marking_threads());
+
+ CMRootRegionScanTask task(this);
+ if (parallel_marking_threads() > 0) {
+ _parallel_workers->set_active_workers((int) active_workers);
+ _parallel_workers->run_task(&task);
+ } else {
+ task.work(0);
+ }
+
+ // It's possible that has_aborted() is true here without actually
+ // aborting the survivor scan earlier. This is OK as it's
+ // mainly used for sanity checking.
+ root_regions()->scan_finished();
+ }
+}
+
void ConcurrentMark::markFromRoots() {
// we might be tempted to assert that:
// assert(asynch == !SafepointSynchronize::is_at_safepoint(),