Index: oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/Compactor.java
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/Compactor.java	(revision 1701579)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/Compactor.java	(working copy)
@@ -83,7 +83,7 @@
 
     public Compactor(SegmentWriter writer, boolean cloneBinaries) {
         this.writer = writer;
-        this.map = new CompactionMap(100000, writer.getTracker());
+        this.map = new CompactionMap(writer.getTracker());
         this.cloneBinaries = cloneBinaries;
     }
 
@@ -95,8 +95,10 @@
     }
 
     public SegmentNodeState compact(NodeState before, NodeState after) {
+        progressStart();
         SegmentNodeState compacted = process(before, after).getNodeState();
         writer.flush();
+        progressDone();
         return compacted;
     }
 
@@ -105,6 +107,37 @@
         return map;
     }
 
+    // progress reports
+
+    private long progress = 0;
+
+    private int logAt = Integer.getInteger("compaction-progress-log", 15000);
+
+    private long start = 0;
+
+    private void progressStart() {
+        progress = 0;
+        start = System.currentTimeMillis();
+    }
+
+    private void progressNewNode() {
+        if (++progress % logAt == 0) {
+            logProgress(start);
+            start = System.currentTimeMillis();
+        }
+    }
+
+    private void progressDone() {
+        logProgress(start);
+    }
+
+    private void logProgress(long start) {
+        log.warn("Compacted {} nodes in {} ms.", progress,
+                System.currentTimeMillis() - start);
+    }
+
+    // ----
+
     private class CompactDiff extends ApplyDiff {
 
         /**
@@ -130,6 +163,7 @@
             } else {
                 this.path = null;
             }
+            progressNewNode();
         }
 
         @Override