count disk reads

block-storage/src/main/java/org/lucares/pdb/diskstorage/DiskStorage.java

@@ -53,6 +53,7 @@ public class DiskStorage implements AutoCloseable {
         try {
             LOGGER.trace("read block={} file={}", blockOffset, relativeDatabaseFileForLogging);
 
+            DiskStoreStats.incrementDiskRead();
             final var byteBuffer = fileChannel.map(MapMode.READ_WRITE, blockOffset, blockSize);
 
             return new DiskBlock(blockOffset, byteBuffer);
@@ -227,6 +228,7 @@ public class DiskStorage implements AutoCloseable {
 
     private FreeListNode readFreeListNode(final long freeListNodePosition) throws IOException {
         final var freeListNode = ByteBuffer.allocate(FREE_LIST_NODE_SIZE);
+        DiskStoreStats.incrementDiskRead();
         fileChannel.read(freeListNode, freeListNodePosition);
         final long offset = freeListNodePosition;
         final long next = freeListNode.getLong(FREE_LIST_NEXT_POINTER);
@@ -250,6 +252,7 @@ public class DiskStorage implements AutoCloseable {
 
     private long readFreeListRootNodePosition() throws IOException {
         final var freeListFirstBlock = ByteBuffer.allocate(8);
+        DiskStoreStats.incrementDiskRead();
         fileChannel.read(freeListFirstBlock, FREE_LIST_ROOT_OFFSET);
         return freeListFirstBlock.getLong(0);
     }

block-storage/src/main/java/org/lucares/pdb/diskstorage/DiskStoreStats.java

@@ -0,0 +1,24 @@
+package org.lucares.pdb.diskstorage;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+public class DiskStoreStats {
+    private static final AtomicLong diskRead = new AtomicLong(0);
+
+    public static void incrementDiskRead() {
+        diskRead.incrementAndGet();
+    }
+
+    public static void resetDiskRead() {
+        diskRead.set(0);
+    }
+
+    public static long getDiskRead() {
+        return diskRead.get();
+    }
+
+    public static long getAndResetDiskRead() {
+
+        return diskRead.getAndSet(0);
+    }
+}