1 /*

     2  * Copyright (c) 2012, 2014, 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 

    26 package com.sun.tools.sjavac.server;

    27 

    28 import java.util.concurrent.ExecutorService;

    29 import java.util.concurrent.Executors;

    30 import java.util.concurrent.Semaphore;

    31 import java.util.Stack;

    32 import java.util.concurrent.Future;

    33 

    34 import com.sun.tools.sjavac.comp.JavacServiceImpl;

    35 

    36 /** The compiler pool maintains compiler threads.

    37  *

    38  * <p><b>This is NOT part of any supported API.

    39  * If you write code that depends on this, you do so at your own

    40  * risk.  This code and its internal interfaces are subject to change

    41  * or deletion without notice.</b></p>

    42  */

    43 public class CompilerPool {

    44     // The javac server that created this pool.

    45     private JavacServer javacServer;

    46     // A semaphore protecting the poolsize number of threads.

    47     private Semaphore available;

    48     // The stack of compiler threads.

    49     private Stack<CompilerThread> compilers = new Stack<>();

    50     // And the executor server to spawn threads.

    51     private final ExecutorService executorPool;

    52     // How many requests are active right now?

    53     private int concurrentRequests = 0;

    54     // When was the last request finished?

    55     private long lastRequestFinished = 0;

    56     // The total number of requests to this pool.

    57     private int numRequests = 0;

    58     // Protect access to the three above values.

    59     private static final Object conc = new Object();

    60 

    61     /**

    62      * Return the javac server that this pool belongs to.

    63      */

    64     public JavacServer getJavacServer() {

    65         return javacServer;

    66     }

    67 

    68     /**

    69      * Return how many threads are running at this very moment.

    70      */

    71     public int numActiveRequests()

    72     {

    73         synchronized (conc) {

    74             return concurrentRequests;

    75         }

    76     }

    77 

    78     /**

    79      * Return when the last request was finished.

    80      * I.e. the pool has been idle since.

    81      */

    82     public long lastRequestFinished()

    83     {

    84         synchronized (conc) {

    85             return lastRequestFinished;

    86         }

    87     }

    88 

    89     /**

    90      * Up the number of active requests.

    91      */

    92     public int startRequest() {

    93         int n;

    94         synchronized (conc) {

    95             concurrentRequests++;

    96             numRequests++;

    97             n = numRequests;

    98         }

    99         return n;

   100     }

   101 

   102     /**

   103      * Down the number of active requests. Return the current time.

   104      */

   105     public long stopRequest() {

   106         synchronized (conc) {

   107             concurrentRequests--;

   108             lastRequestFinished = System.currentTimeMillis();

   109         }

   110         return lastRequestFinished;

   111     }

   112 

   113     /**

   114      * Create a new compiler pool.

   115      */

   116     CompilerPool(int poolsize, JavacServer server) {

   117         available = new Semaphore(poolsize, true);

   118         javacServer = server;

   119         executorPool = Executors.newFixedThreadPool(poolsize);

   120         lastRequestFinished = System.currentTimeMillis();

   121     }

   122 

   123     /**

   124      * Execute a compiler thread.

   125      */

   126     public void execute(CompilerThread ct) {

   127         executorPool.execute(ct);

   128     }

   129 

   130     /**

   131      * Execute a minor task, for example generating bytecodes and writing them to disk,

   132      * that belong to a major compiler thread task.

   133      */

   134     public Future<?> executeSubtask(CompilerThread t, Runnable r) {

   135         return executorPool.submit(r);

   136     }

   137 

   138     /**

   139      * Shutdown the pool.

   140      */

   141     public void shutdown() {

   142         executorPool.shutdown();

   143     }

   144 

   145     /**

   146      * Acquire a compiler thread from the pool, or block until a thread is available.

   147      * If the pools is empty, create a new thread, but never more than is "available".

   148      */

   149     public CompilerThread grabCompilerThread() throws InterruptedException {

   150         available.acquire();

   151         if (compilers.empty()) {

   152             return new CompilerThread(this, new JavacServiceImpl(javacServer));

   153         }

   154         return compilers.pop();

   155     }

   156 

   157     /**

   158      * Return the specified compiler thread to the pool.

   159      */

   160     public void returnCompilerThread(CompilerThread h) {

   161         compilers.push(h);

   162         available.release();

   163     }

   164 }

   165