Fixes #11432 - Review number of acceptor threads.

jetty-core/jetty-server/src/main/java/org/eclipse/jetty/server/AbstractConnector.java

@@ -196,7 +196,7 @@ public AbstractConnector(
 
         int cores = ProcessorUtils.availableProcessors();
         if (acceptors < 0)
-            acceptors = Math.max(1, Math.min(4, cores / 8));
+            acceptors = 1;
         if (acceptors > cores)
             LOG.warn("Acceptors should be <= availableProcessors: {} ", this);
         _acceptors = new Thread[acceptors];

jetty-core/jetty-server/src/main/java/org/eclipse/jetty/server/LocalConnector.java

@@ -48,7 +48,7 @@ public class LocalConnector extends AbstractConnector
 
     public LocalConnector(Server server, Executor executor, Scheduler scheduler, ByteBufferPool bufferPool, int acceptors, ConnectionFactory... factories)
     {
-        super(server, executor, scheduler, bufferPool, acceptors, factories);
+        super(server, executor, scheduler, bufferPool, Math.max(1, acceptors), factories);
         setIdleTimeout(30000);
     }
 

jetty-core/jetty-unixdomain-server/src/main/java/org/eclipse/jetty/unixdomain/server/UnixDomainServerConnector.java

@@ -149,9 +149,17 @@ public void setAcceptedSendBufferSize(int acceptedSendBufferSize)
     protected void doStart() throws Exception
     {
         getBeans(SelectorManager.SelectorManagerListener.class).forEach(selectorManager::addEventListener);
+
         serverChannel = open();
         addBean(serverChannel);
+
         super.doStart();
+
+        if (getAcceptors() == 0)
+        {
+            serverChannel.configureBlocking(false);
+            acceptor.set(selectorManager.acceptor(serverChannel));
+        }
     }
 
     @Override
@@ -200,25 +208,6 @@ public Object getTransport()
     }
 
     private ServerSocketChannel open() throws IOException
-    {
-        ServerSocketChannel serverChannel = openServerSocketChannel();
-        if (getAcceptors() == 0)
-        {
-            serverChannel.configureBlocking(false);
-            acceptor.set(selectorManager.acceptor(serverChannel));
-        }
-        return serverChannel;
-    }
-
-    private void close() throws IOException
-    {
-        ServerSocketChannel serverChannel = this.serverChannel;
-        this.serverChannel = null;
-        IO.close(serverChannel);
-        Files.deleteIfExists(getUnixDomainPath());
-    }
-
-    private ServerSocketChannel openServerSocketChannel() throws IOException
     {
         ServerSocketChannel serverChannel = null;
         if (isInheritChannel())
@@ -234,6 +223,14 @@ private ServerSocketChannel openServerSocketChannel() throws IOException
         return serverChannel;
     }
 
+    private void close() throws IOException
+    {
+        ServerSocketChannel serverChannel = this.serverChannel;
+        this.serverChannel = null;
+        IO.close(serverChannel);
+        Files.deleteIfExists(getUnixDomainPath());
+    }
+
     private ServerSocketChannel bindServerSocketChannel() throws IOException
     {
         Path unixDomainPath = getUnixDomainPath();

tests/jetty-jmh/pom.xml

@@ -29,6 +29,10 @@
       <groupId>org.eclipse.jetty</groupId>
       <artifactId>jetty-server</artifactId>
     </dependency>
+    <dependency>
+      <groupId>org.eclipse.jetty</groupId>
+      <artifactId>jetty-slf4j-impl</artifactId>
+    </dependency>
     <dependency>
       <groupId>org.eclipse.jetty</groupId>
       <artifactId>jetty-util</artifactId>
@@ -51,11 +55,6 @@
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-api</artifactId>
     </dependency>
-    <dependency>
-      <groupId>org.eclipse.jetty</groupId>
-      <artifactId>jetty-slf4j-impl</artifactId>
-      <scope>test</scope>
-    </dependency>
   </dependencies>
 
   <build>

tests/jetty-jmh/src/main/java/org/eclipse/jetty/server/jmh/ServerConnectorAcceptBenchmark.java

@@ -0,0 +1,110 @@
+//
+// ========================================================================
+// Copyright (c) 1995 Mort Bay Consulting Pty Ltd and others.
+//
+// This program and the accompanying materials are made available under the
+// terms of the Eclipse Public License v. 2.0 which is available at
+// https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
+// which is available at https://www.apache.org/licenses/LICENSE-2.0.
+//
+// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
+// ========================================================================
+//
+
+package org.eclipse.jetty.server.jmh;
+
+import java.net.InetSocketAddress;
+import java.nio.channels.SocketChannel;
+import java.nio.charset.StandardCharsets;
+import java.util.concurrent.atomic.LongAdder;
+
+import org.eclipse.jetty.http.HttpStatus;
+import org.eclipse.jetty.http.HttpTester;
+import org.eclipse.jetty.server.Handler;
+import org.eclipse.jetty.server.Request;
+import org.eclipse.jetty.server.Response;
+import org.eclipse.jetty.server.Server;
+import org.eclipse.jetty.server.ServerConnector;
+import org.eclipse.jetty.util.Callback;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.TearDown;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+import org.openjdk.jmh.runner.options.TimeValue;
+
+@State(Scope.Benchmark)
+public class ServerConnectorAcceptBenchmark
+{
+    public static void main(String[] args) throws Exception
+    {
+        Options opt = new OptionsBuilder()
+            .include(ServerConnectorAcceptBenchmark.class.getSimpleName())
+            .warmupIterations(10)
+            .warmupTime(TimeValue.milliseconds(500))
+            .measurementIterations(10)
+            .measurementTime(TimeValue.milliseconds(500))
+            .forks(1)
+            .threads(20)
+            .build();
+        new Runner(opt).run();
+    }
+
+//    @Param({"0", "1", "2", "4"})
+    @Param({"4", "2", "1", "0"})
+    public int acceptors;
+
+    final LongAdder count = new LongAdder();
+
+    Server server;
+    ServerConnector connector;
+
+    @Setup
+    public void prepare() throws Exception
+    {
+        server = new Server();
+        connector = new ServerConnector(server, acceptors, -1);
+        server.addConnector(connector);
+        server.setHandler(new Handler.Abstract()
+        {
+            @Override
+            public boolean handle(Request request, Response response, Callback callback) throws Exception
+            {
+                callback.succeeded();
+                return true;
+            }
+        });
+        server.start();
+    }
+
+    @TearDown
+    public void dispose() throws Exception
+    {
+        System.err.println("count = " + count.sum());
+        server.stop();
+    }
+
+    @Benchmark
+    @BenchmarkMode({Mode.Throughput})
+    public void accept() throws Exception
+    {
+        count.increment();
+        try (SocketChannel channel = SocketChannel.open(new InetSocketAddress("localhost", connector.getLocalPort())))
+        {
+            channel.write(StandardCharsets.US_ASCII.encode("GET / HTTP/1.0\r\n\r\n"));
+            HttpTester.Response response = HttpTester.parseResponse(HttpTester.from(channel));
+            if (response.getStatus() != HttpStatus.OK_200)
+                System.err.println("x = " + response);
+        }
+        catch (Throwable x)
+        {
+            System.err.println("x = " + x);
+        }
+    }
+}