Allow disabling io_uring sendfile support via a system property.

Author: dreamlike-ocean

vertx-core/src/main/java/io/vertx/core/impl/SysProps.java

@@ -116,6 +116,17 @@ public String get() {
   JACKSON_DEFAULT_READ_MAX_NAME_LEN("vertx.jackson.defaultReadMaxNameLength"),
   JACKSON_DEFAULT_READ_MAX_TOKEN_COUNT("vertx.jackson.defaultMaxTokenCount"),
 
+  /**
+   * Disable {@code sendfile} support for the io_uring transport.
+   * <p>
+   * When this system property is set to {@code true}, Vert.x will avoid using the
+   * io_uring splice path.
+   * <p>
+   * This is useful because io_uring splice can be slower than the
+   * epoll {@code sendfile} in some workloads.
+   * See <a href="https://github.com/netty/netty/issues/15747">Netty issue 15747</a>.
+   */
+  DISABLE_IO_URING_SENDFILE("vertx.disableIoUringSendfile"),
   ;
 
   public final String name;

vertx-core/src/main/java/io/vertx/core/impl/transports/IoUringTransport.java

@@ -18,6 +18,7 @@
 import io.netty.channel.unix.DomainSocketAddress;
 import io.netty.channel.uring.*;
 import io.vertx.core.datagram.DatagramSocketOptions;
+import io.vertx.core.impl.SysProps;
 import io.vertx.core.net.TcpOptions;
 import io.vertx.core.net.impl.SocketAddressImpl;
 import io.vertx.core.spi.transport.Transport;
@@ -29,6 +30,8 @@
  */
 public class IoUringTransport implements Transport {
 
+  private static final boolean DISABLE_SENDFILE = SysProps.DISABLE_IO_URING_SENDFILE.getBoolean();
+
   private static volatile int pendingFastOpenRequestsThreshold = 256;
 
   /**
@@ -62,7 +65,7 @@ public boolean supportsDomainSockets() {
 
   @Override
   public boolean supportFileRegion() {
-    return IoUring.isSpliceSupported();
+    return IoUring.isSpliceSupported() && !DISABLE_SENDFILE;
   }
 
   @Override