src/java.base/linux/classes/sun/nio/ch/DefaultPollerProvider.java

@@ -23,42 +23,89 @@
   * questions.
   */
  package sun.nio.ch;
  
  import java.io.IOException;
+ import jdk.internal.access.JavaLangAccess;
+ import jdk.internal.access.SharedSecrets;
  import jdk.internal.vm.ContinuationSupport;
  
  /**
   * Default PollerProvider for Linux.
   */
  class DefaultPollerProvider extends PollerProvider {
-     DefaultPollerProvider() { }
+     private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
  
-     @Override
-     Poller.Mode defaultPollerMode() {
-         if (ContinuationSupport.isSupported()) {
-             return Poller.Mode.VTHREAD_POLLERS;
+     private static final boolean USE_IOURING;
+     private static final boolean USE_IORING_OP_READ;
+     private static final boolean USE_IORING_OP_WRITE;
+     static {
+         String s = System.getProperty("jdk.io_uring");
+         if ("".equals(s) || Boolean.parseBoolean(s)) {
+             USE_IOURING = true;
+             s = System.getProperty("jdk.io_uring.read");
+             USE_IORING_OP_READ = "".equals(s) || Boolean.parseBoolean(s);
+             s = System.getProperty("jdk.io_uring.write");
+             USE_IORING_OP_WRITE = "".equals(s) || Boolean.parseBoolean(s);
          } else {
-             return Poller.Mode.SYSTEM_THREADS;
+             USE_IOURING = false;
+             USE_IORING_OP_READ = false;
+             USE_IORING_OP_WRITE = false;
          }
      }
  
+     DefaultPollerProvider(Poller.Mode mode) {
+         super(mode);
+     }
+ 
+     DefaultPollerProvider() {
+         boolean usingBuiltinScheduler = ContinuationSupport.isSupported()
+                 && (JLA.defaultVirtualThreadScheduler() == JLA.builtinVirtualThreadScheduler());
+         this(usingBuiltinScheduler ? Poller.Mode.VTHREAD_POLLERS : Poller.Mode.SYSTEM_THREADS);
+     }
+ 
      @Override
-     int defaultReadPollers(Poller.Mode mode) {
+     int defaultReadPollers() {
          int ncpus = Runtime.getRuntime().availableProcessors();
-         if (mode == Poller.Mode.VTHREAD_POLLERS) {
-             return Math.min(Integer.highestOneBit(ncpus), 32);
-         } else {
-             return Math.max(Integer.highestOneBit(ncpus / 4), 1);
-         }
+         return switch (pollerMode()) {
+             case SYSTEM_THREADS  -> Math.max(Integer.highestOneBit(ncpus / 4), 1);
+             case VTHREAD_POLLERS -> Math.min(Integer.highestOneBit(ncpus), 32);
+             default              -> super.defaultReadPollers();
+         };
      }
  
      @Override
      Poller readPoller(boolean subPoller) throws IOException {
-         return new EPollPoller(subPoller, true);
+         Poller.Mode mode = pollerMode();
+         if (USE_IOURING) {
+             // read poller is system thread in SYSTEM_THREADS mode
+             boolean supportReadOps = USE_IORING_OP_READ
+                     && ((mode == Poller.Mode.SYSTEM_THREADS) || subPoller);
+             return new IoUringPoller(mode, subPoller, true, supportReadOps);
+         } else {
+             return new EPollPoller(mode, subPoller, true);
+         }
      }
  
      @Override
      Poller writePoller(boolean subPoller) throws IOException {
-         return new EPollPoller(subPoller, false);
+         Poller.Mode mode = pollerMode();
+         if (USE_IOURING) {
+             // write poller is system thread in SYSTEM_THREADS and POLLER_PER_CARRIER modes
+             boolean supportWriteOps = USE_IORING_OP_WRITE
+                     && ((mode != Poller.Mode.VTHREAD_POLLERS) || subPoller);
+             return new IoUringPoller(mode, subPoller, false, supportWriteOps);
+         } else {
+             return new EPollPoller(mode, subPoller, false);
+         }
+     }
+ 
+     @Override
+     boolean supportReadOps() {
+         return USE_IORING_OP_READ;
+     }
+ 
+     @Override
+     boolean supportWriteOps() {
+         return USE_IORING_OP_WRITE;
      }
  }