1 /*
 2  * Copyright (c) 2017, 2023, Oracle and/or its affiliates. All rights reserved.
 3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 4  *
 5  * This code is free software; you can redistribute it and/or modify it
 6  * under the terms of the GNU General Public License version 2 only, as
 7  * published by the Free Software Foundation.  Oracle designates this
 8  * particular file as subject to the "Classpath" exception as provided
 9  * by Oracle in the LICENSE file that accompanied this code.
10  *
11  * This code is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
16  *
17  * You should have received a copy of the GNU General Public License version
18  * 2 along with this work; if not, write to the Free Software Foundation,
19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20  *
21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22  * or visit www.oracle.com if you need additional information or have any
23  * questions.
24  */
25 package sun.nio.ch;
26 
27 import java.io.IOException;
28 import jdk.internal.vm.ContinuationSupport;
29 
30 /**
31  * Default PollerProvider for Linux.
32  */
33 class DefaultPollerProvider extends PollerProvider {
34     private static final boolean USE_IOURING;
35     static {
36         String s = System.getProperty("jdk.io_uring");
37         USE_IOURING = "".equals(s) || Boolean.parseBoolean(s);
38     }
39 
40     DefaultPollerProvider() { }
41 
42     @Override
43     Poller.Mode defaultPollerMode() {
44         if (ContinuationSupport.isSupported()) {
45             return USE_IOURING ? Poller.Mode.PER_CARRIER : Poller.Mode.VTHREAD_POLLERS;
46         } else {
47             return Poller.Mode.SYSTEM_THREADS;
48         }
49     }
50 
51     @Override
52     int defaultReadPollers(Poller.Mode mode) {
53         int ncpus = Runtime.getRuntime().availableProcessors();
54         return switch (mode) {
55             case SYSTEM_THREADS  -> Math.max(Integer.highestOneBit(ncpus / 4), 1);
56             case VTHREAD_POLLERS -> Math.min(Integer.highestOneBit(ncpus), 32);
57             default              -> super.defaultReadPollers(mode);
58         };
59     }
60 
61     @Override
62     Poller readPoller(boolean subPoller) throws IOException {
63         if (USE_IOURING) {
64             return new IoUringPoller(subPoller, true);
65         } else {
66             return new EPollPoller(subPoller, true);
67         }
68     }
69 
70     @Override
71     Poller writePoller(boolean subPoller) throws IOException {
72         if (USE_IOURING) {
73             return new IoUringPoller(subPoller, false);
74         } else {
75             return new EPollPoller(subPoller, false);
76         }
77     }
78 }