count memory mappings in container

1 files changed, 22 insertions, 0 deletions

diff --git a/container-disc/src/main/java/com/yahoo/container/jdisc/metric/MetricUpdater.java b/container-disc/src/main/java/com/yahoo/container/jdisc/metric/MetricUpdater.java
index ab6e0b04085..e23844c65b7 100644
--- a/container-disc/src/main/java/com/yahoo/container/jdisc/metric/MetricUpdater.java
+++ b/container-disc/src/main/java/com/yahoo/container/jdisc/metric/MetricUpdater.java
@@ -3,6 +3,9 @@ package com.yahoo.container.jdisc.metric;
 
 import java.util.Timer;
 import java.util.TimerTask;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.Files;
 
 import com.google.inject.Inject;
 import com.yahoo.component.AbstractComponent;
@@ -23,6 +26,7 @@ public class MetricUpdater extends AbstractComponent {
     private static final String MANHATTAN_FREE_MEMORY_BYTES = "mem.heap.free";
     private static final String MANHATTAN_USED_MEMORY_BYTES = "mem.heap.used";
     private static final String MANHATTAN_TOTAL_MEMORY_BYTES = "mem.heap.total";
+    private static final String MEMORY_MAPPINGS_COUNT = "memory_mappings_count";
 
     private final Metric metric;
     private final Timer timer = new Timer();
@@ -60,6 +64,24 @@ public class MetricUpdater extends AbstractComponent {
             metric.set(MANHATTAN_FREE_MEMORY_BYTES, freeMemory, null);
             metric.set(MANHATTAN_USED_MEMORY_BYTES, usedMemory, null);
             metric.set(MANHATTAN_TOTAL_MEMORY_BYTES, totalMemory, null);
+            metric.set(MEMORY_MAPPINGS_COUNT, count_mappings(), null);
+        }
+
+        // Note: Linux-specific
+        private long count_mappings() {
+            long count = 0;
+            try {
+                Path p = Paths.get("/proc/self/maps");
+                byte[] data = Files.readAllBytes(p);
+                for (byte b : data) {
+                    if (b == '\n') {
+                        ++count;
+                    }
+                }
+            } catch (Exception e) {
+                System.err.println("Could not read /proc/self/maps: " + e);
+            }
+            return count;
         }
     }
 }