8051973: Eager reclaim leaves marks of marked but reclaimed objects on the next bitmap

Summary: Eager reclaim also needs to clear marks of eagerly reclaimed regions if they have already been marked during concurrent mark.
Reviewed-by: jmasa

src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -6578,6 +6578,9 @@ class G1FreeHumongousRegionClosure : public HeapRegionClosure {
 
     G1CollectedHeap* g1h = G1CollectedHeap::heap();
 
+    oop obj = (oop)r->bottom();
+    CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
+
     // The following checks whether the humongous object is live are sufficient.
     // The main additional check (in addition to having a reference from the roots
     // or the young gen) is whether the humongous object has a remembered set entry.
@@ -6614,37 +6617,41 @@ class G1FreeHumongousRegionClosure : public HeapRegionClosure {
         g1h->humongous_region_is_always_live(region_idx)) {
 
       if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
-        gclog_or_tty->print_cr("Live humongous %d region %d with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is dead-bitmap %d live-other %d obj array %d",
+        gclog_or_tty->print_cr("Live humongous %d region %d with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
                                r->isHumongous(),
                                region_idx,
                                r->rem_set()->occupied(),
                                r->rem_set()->strong_code_roots_list_length(),
-                               g1h->mark_in_progress() && !g1h->g1_policy()->during_initial_mark_pause(),
+                               next_bitmap->isMarked(r->bottom()),
                                g1h->humongous_is_live(region_idx),
-                               oop(r->bottom())->is_objArray()
+                               obj->is_objArray()
                               );
       }
 
       return false;
     }
 
-    guarantee(!((oop)(r->bottom()))->is_objArray(),
+    guarantee(!obj->is_objArray(),
               err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
                       r->bottom()));
 
     if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
-      gclog_or_tty->print_cr("Reclaim humongous region %d start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is dead-bitmap %d live-other %d obj array %d",
+      gclog_or_tty->print_cr("Reclaim humongous region %d start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
                              r->isHumongous(),
                              r->bottom(),
                              region_idx,
                              r->region_num(),
                              r->rem_set()->occupied(),
                              r->rem_set()->strong_code_roots_list_length(),
-                             g1h->mark_in_progress() && !g1h->g1_policy()->during_initial_mark_pause(),
+                             next_bitmap->isMarked(r->bottom()),
                              g1h->humongous_is_live(region_idx),
-                             oop(r->bottom())->is_objArray()
+                             obj->is_objArray()
                             );
     }
+    // Need to clear mark bit of the humongous object if already set.
+    if (next_bitmap->isMarked(r->bottom())) {
+      next_bitmap->clear(r->bottom());
+    }
     _freed_bytes += r->used();
     r->set_containing_set(NULL);
     _humongous_regions_removed.increment(1u, r->capacity());

test/gc/g1/TestEagerReclaimHumongousRegions2.java

+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * 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.
+ */
+
+/*
+ * @test TestEagerReclaimHumongousRegions2
+ * @bug 8051973
+ * @summary Test to make sure that eager reclaim of humongous objects correctly clears
+ * mark bitmaps at reclaim.
+ * @key gc
+ * @library /testlibrary
+ */
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.Random;
+
+import com.oracle.java.testlibrary.OutputAnalyzer;
+import com.oracle.java.testlibrary.ProcessTools;
+
+// An object that has a few references to other instances to slow down marking.
+class ObjectWithSomeRefs {
+    public ObjectWithSomeRefs other1;
+    public ObjectWithSomeRefs other2;
+    public ObjectWithSomeRefs other3;
+    public ObjectWithSomeRefs other4;
+}
+
+class ReclaimRegionFast {
+    public static final int M = 1024*1024;
+
+    public static LinkedList<Object> garbageList = new LinkedList<Object>();
+
+    public static void genGarbage(Object large) {
+        for (int i = 0; i < 64*1024; i++) {
+            Object[] garbage = new Object[50];
+            garbage[0] = large;
+            garbageList.add(garbage);
+        }
+        garbageList.clear();
+    }
+
+    public static ArrayList<ObjectWithSomeRefs> longList = new ArrayList<ObjectWithSomeRefs>();
+
+    public static void main(String[] args) {
+
+        for (int i = 0; i < 16*1024; i++) {
+             longList.add(new ObjectWithSomeRefs());
+        }
+
+        Random rnd = new Random();
+        for (int i = 0; i < longList.size(); i++) {
+             int len = longList.size();
+             longList.get(i).other1 = longList.get(rnd.nextInt(len));
+             longList.get(i).other2 = longList.get(rnd.nextInt(len));
+             longList.get(i).other3 = longList.get(rnd.nextInt(len));
+             longList.get(i).other4 = longList.get(rnd.nextInt(len));
+        }
+
+        int[] large1 = new int[M];
+        int[] large2 = null;
+        int[] large3 = null;
+        int[] large4 = null;
+
+        Object ref_from_stack = large1;
+
+        for (int i = 0; i < 20; i++) {
+            // A set of large objects that will be reclaimed eagerly - and hopefully marked.
+            large1 = new int[M - 20];
+            large2 = new int[M - 20];
+            large3 = new int[M - 20];
+            large4 = new int[M - 20];
+            genGarbage(large1);
+            // Make sure that the compiler cannot completely remove
+            // the allocation of the large object until here.
+            System.out.println(large1 + " " + large2 + " " + large3 + " " + large4);
+        }
+
+        // Keep the reference to the first object alive.
+        System.out.println(ref_from_stack);
+    }
+}
+
+public class TestEagerReclaimHumongousRegions2 {
+    public static void main(String[] args) throws Exception {
+        ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(
+            "-XX:+UseG1GC",
+            "-Xms128M",
+            "-Xmx128M",
+            "-Xmn2M",
+            "-XX:G1HeapRegionSize=1M",
+            "-XX:InitiatingHeapOccupancyPercent=0", // Want to have as much as possible initial marks.
+            "-XX:+PrintGC",
+            "-XX:+VerifyAfterGC",
+            "-XX:ConcGCThreads=1", // Want to make marking as slow as possible.
+            "-XX:+IgnoreUnrecognizedVMOptions", // G1VerifyBitmaps is develop only.
+            "-XX:+G1VerifyBitmaps",
+            ReclaimRegionFast.class.getName());
+        OutputAnalyzer output = new OutputAnalyzer(pb.start());
+        output.shouldHaveExitValue(0);
+    }
+}
+