perf: batch selector wakeup call when adding bulk requests

evcache-core/src/main/java/net/spy/memcached/EVCacheConnection.java

@@ -4,6 +4,7 @@
 import java.net.InetSocketAddress;
 import java.nio.channels.CancelledKeyException;
 import java.nio.channels.ClosedSelectorException;
+import java.nio.channels.Selector;
 import java.util.Collection;
 import java.util.ConcurrentModificationException;
 import java.util.List;
@@ -17,12 +18,14 @@
 
 public class EVCacheConnection extends MemcachedConnection {
     private static final Logger log = LoggerFactory.getLogger(EVCacheConnection.class);
+    private final net.spy.memcached.compat.log.Logger spyLogger;
 
     public EVCacheConnection(String name, int bufSize, ConnectionFactory f,
             List<InetSocketAddress> a, Collection<ConnectionObserver> obs,
             FailureMode fm, OperationFactory opfactory) throws IOException {
         super(bufSize, f, a, obs, fm, opfactory);
         setName(name);
+        spyLogger = super.getLogger();
     }
 
     @Override
@@ -76,9 +79,42 @@ protected void addOperation(final MemcachedNode node, final Operation o) {
 
     @Override
     public void addOperations(Map<MemcachedNode, Operation> ops) {
-        super.addOperations(ops);
-        for (MemcachedNode node : ops.keySet()) {
-            ((EVCacheNode) node).incrOps();
+        // Directly inline this operation, copied down from parent implementation.
+        final String OVERALL_REQUEST_METRIC = "[MEM] Request Rate: All";
+
+        // We want to avoid selector.wakeup() being called repeatedly if we can avoid it.
+        // The epoll selector takes a lock underneath even if it determines that no system
+        // call is required. This is unfortunately contending with the memcached loop which
+        // is prevented from progressing the select() while a wakeup() check is in flight.
+
+        boolean addedOne = false;
+        try {
+            for (Map.Entry<MemcachedNode, Operation> me : ops.entrySet()) {
+                MemcachedNode node = me.getKey();
+                Operation o = me.getValue();
+
+                if (!node.isAuthenticated()) {
+                    retryOperation(o);
+                    continue;
+                }
+
+                addedOne = true;
+
+                o.setHandlingNode(node);
+                o.initialize();
+                node.addOp(o);
+                addedQueue.offer(node);
+
+                ((EVCacheNode) node).incrOps();
+                metrics.markMeter(OVERALL_REQUEST_METRIC);
+                // retain the existing logger configuration
+                spyLogger.debug("Added %s to %s", o, node);
+            }
+        } finally {
+            if (addedOne) {
+                Selector s = selector.wakeup();
+                assert s == selector : "Wakeup returned the wrong selector.";
+            }
         }
     }