异步调用和oneway调用，信号量调整为2048， 因为有可能某个消费者分配的队列大于信号量，就会导致拉消息效率下降，甚至延时。

修改为2048，同时也会带来坏处， 异步调用的流控阀值会变大， 流控效果下降， 如果客户端调用tps超出服务器处理能力， 可能会触发服务器流控。

Author: vintagewang

rocketmq-remoting/src/main/java/com/alibaba/rocketmq/remoting/netty/NettyRemotingAbstract.java

@@ -111,7 +111,7 @@ public void run() {
             while (!this.isStoped()) {
                 try {
                     NettyEvent event = this.eventQueue.poll(3000, TimeUnit.MILLISECONDS);
-                    if (event != null) {
+                    if (event != null && listener != null) {
                         switch (event.getType()) {
                         case IDLE:
                             listener.onChannelIdle(event.getRemoteAddr(), event.getChannel());

rocketmq-remoting/src/main/java/com/alibaba/rocketmq/remoting/netty/NettySystemConfig.java

@@ -20,10 +20,10 @@ public class NettySystemConfig {
     public static final String SystemPropertyClientAsyncSemaphoreValue = //
             "com.rocketmq.remoting.clientAsyncSemaphoreValue";
     public static int ClientAsyncSemaphoreValue = //
-            Integer.parseInt(System.getProperty(SystemPropertyClientAsyncSemaphoreValue, "128"));
+            Integer.parseInt(System.getProperty(SystemPropertyClientAsyncSemaphoreValue, "2048"));
 
     public static final String SystemPropertyClientOnewaySemaphoreValue = //
             "com.rocketmq.remoting.clientOnewaySemaphoreValue";
     public static int ClientOnewaySemaphoreValue = //
-            Integer.parseInt(System.getProperty(SystemPropertyClientOnewaySemaphoreValue, "256"));
+            Integer.parseInt(System.getProperty(SystemPropertyClientOnewaySemaphoreValue, "2048"));
 }