[heap] Add tracing for age_marks upon evacuation

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 2973 matching lines @@
   bool success = false;
   DCHECK(p->IsEvacuationCandidate() || p->InNewSpace());
   int saved_live_bytes = p->LiveBytes();
   double evacuation_time;
   {
     AlwaysAllocateScope always_allocate(heap()->isolate());
     TimedScope timed_scope(&evacuation_time);
     success = collector_->VisitLiveObjects(p, visitor, kClearMarkbits);
   }
   if (FLAG_trace_evacuation) {
+    const char age_mark_tag =
+        !p->InNewSpace()
+            ? 'x'
+            : !p->IsFlagSet(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK)
+                  ? '>'
+                  : !p->ContainsLimit(heap()->new_space()->age_mark()) ? '<'
+                                                                       : '#';
     PrintIsolate(heap()->isolate(),
-                 "evacuation[%p]: page=%p new_space=%d executable=%d "
-                 "live_bytes=%d time=%f\n",
-                 this, p, p->InNewSpace(),
+                 "evacuation[%p]: page=%p new_space=%d age_mark_tag=%c "
+                 "executable=%d live_bytes=%d time=%f\n",
+                 this, p, p->InNewSpace(), age_mark_tag,
                  p->IsFlagSet(MemoryChunk::IS_EXECUTABLE), saved_live_bytes,
                  evacuation_time);
   }
   if (success) {
     ReportCompactionProgress(evacuation_time, saved_live_bytes);
   }
   return success;
 }
 
 bool MarkCompactCollector::Evacuator::EvacuatePage(MemoryChunk* chunk) {
@@ skipping 798 matching lines @@
     MarkBit mark_bit = Marking::MarkBitFrom(host);
     if (Marking::IsBlack(mark_bit)) {
       RelocInfo rinfo(isolate(), pc, RelocInfo::CODE_TARGET, 0, host);
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8