语言基础 / Java40 分钟 读完 (大约 5948 个字)

Ubuntu编译glibc库来验证Synchronized锁优化效果

0.前言


当然你可以说通过JOL查看对象的头信息，当然那个也是一种方法，但那个只能说明是这种状态，没有过程，本次主要结合来验证，Synchronized 关键字锁的状态：无锁、偏向锁、轻量级锁、重量级锁

基于Ubuntu16测试成功。18测试失败，centos没有测试




主要是在Java调用系统函数的时候，打印log。但是在Java里面打印线程ID是JVM层面的。需要自己实现一个native方法，在java层面调用。最后对比对应的PID 和TID，发现查看当前线程调用了几次系统锁
Java 的重量级级锁都是通过glibc库的pthread_mutex_lock函数实现的，是在和操作系统级别的锁。

glibc库


glibc是linux系统中最底层的api，几乎其它任何运行库都会依赖于glibc。glibc除了封装linux操作系统所提供的系统服务外，它本身也提供了许多其它一些必要功能服务的实现。

  • 操作系统底层库

int pthread_mutex_lock(pthread_mutex_t *mutex);


pthread_mutex_lock()返回时，该互斥锁已被锁定。线程调用该函数让互斥锁上锁，如果该互斥锁已被另一个线程锁定和拥有，则调用该线程将阻塞，直到该互斥锁变为可用为止。 对于 Solaris线程，请参见mutex_lock 语法

  • 会阻塞


我们可以从JVM 源码中看到调用

ThreadCritical::ThreadCritical

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ThreadCritical::ThreadCritical() {
  pthread_t self = pthread_self();
  if (self != tc_owner) {
    int ret = pthread_mutex_lock(&tc_mutex);
    guarantee(ret == 0, "fatal error with pthread_mutex_lock()");
    assert(tc_count == 0, "Lock acquired with illegal reentry count.");
    tc_owner = self;
  }
  tc_count++;
}


这个是底层系统库，我们是看不到源码的，只能自己下载。可以在glibc/nptl/phread_mutex_lock.c里看到实现。
我尝试就是在这里函数里加上自己的log

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int __pthread_mutex_lock (pthread_mutex_t *mutex)
{ 
  //打印log
  fprintf(stdout,"pthread_mutex_lock log  PID = %d TID = %lu  mutex = %p \n",getpid(),pthread_self(),&mutex); 
  ---

1. 查看自己的glibc版本

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root@189415df5c51:/lib/x86_64-linux-gnu# pwd
/lib/x86_64-linux-gnu
root@189415df5c51:/lib/x86_64-linux-gnu# ls -l libc.so.6
lrwxrwxrwx 1 root root 12 Feb  5  2019 libc.so.6 -> libc-2.23.so
root@189415df5c51:/lib/x86_64-linux-gnu#

2.最好下载同一个版本，编译glibc版本


https://ftp.gnu.org/gnu/glibc/?C=M;O=A
目录可以自己变化，但是glibc不让在源码目录下面编译 会报 Makeconfig:42: *** missing separator. Stop




若有必要，可以参考 Linux源码包的一般安装步

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mkdir build
cd build
./../configure  --prefix = usr/local/glibc 
make
make install

3.修改替换 编译


vim pthread_mutex_lock.c 添加log

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fprintf(stdout,"pthread_mutex_lock log  PID = %d TID = %lu  mutex = %p \n",getpid(),pthread_self(),&mutex);

4.运行时替换关键库

  • 这里需要注意，搞错了，就不能的话，所有命令都可能用不了了


自己主要修改的是pthread库，所以替换系统的pthread库，find一下

  • 1.查看 /etc/ld.conf.d/x86-gnu*.conf 下的目录
  • 2.因为要替换几个关键文件，直接手动替换会出错，系统库是在动态加载的。copy 一个临时目录，加上了n后缀，做区分。去替换临时目录里面的文件
  • 3.例如我的
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cp /usr/local/glibc23/lib/libpthread.so /usr/lib/x86_64-linux-gnu-n/libpthread.so
cp /usr/local/glibc23/lib/libpthread_nonshared.a /usr/lib/x86_64-linux-gnu-n/libpthread_nonshared.a
cp /usr/local/glibc23/lib/libpthread.a /usr/lib/x86_64-linux-gnu-n/libpthread.a
cp /usr/local/glibc23/lib/libpthread-2.23.so  /lib/x86_64-linux-gnu-n/libpthread-2.23.so
cp /usr/local/glibc23/lib/libpthread.so.0 /lib/x86_64-linux-gnu-n/libpthread.so.0
  • 4.修改 /etc/ld.conf.d/x86-gnu*.conf 里面的链接库路径指向临时目录，不用了可以改回
  • 5.执行ldconfig，生效
  • 6.自己配置java环境
  • 基本任命令都会触发这行log
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root@189415df5c51:/etc/ld.so.conf.d# ls
pthread_mutex_lock log  PID = 62030 TID = 140453473769472 mutex=0x7fbddf6a1948
libc.conf  x86_64-linux-gnu.conf

5.编写Java验证


接下来，就是正常jni流程了

JniTool.java

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package jnitool;

public class JniTool {
    static {
        System.loadLibrary("jnitools");
    }
    public native void getThreadID();
}


这里jnitool必须在 java.library.path这一jvm变量所指向的路径中，
可以通过如下方法获得该变量System.getProperty(“java.library.path”);

生成.h文件，javah -jni jnitool.JniTool


打印java线程的pid和tid，jvm层面

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#include "jnitool_JniTool.h"
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>

JNIEXPORT void JNICALL Java_jnitool_JniTool_getThreadID
  (JNIEnv * env, jobject obj){
        fprintf(stdout,"java_lock log  PID = %d TID = %lu \n",getpid(),pthread_self());
        fflush(stdout);//刷新，防止错位打印
}

使用make编译

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vim makefile

libjnitools.so:
	gcc -lpthread -fPIC -shared -o libjnitools.so  -I /root/jdk1.8.0_221/include/ -I /root/jdk1.8.0_221/include/linux/ ./jnitools.c
  
make

6. 观察不同的锁

  • 主要是对比不同的锁情况下，对操作系统系统锁的调用情况，观察优化效果
  • 当然JVM对锁的优化，是调用系统锁的次数越少越好
  • 听过系统锁的log，直观对比调用pthread_mutex_lock次数
  • 奇怪的是我在docker里面，修改glibc库后，加上jol打印头信息就会卡，所以先验证是什么锁的情况下，再打的log

6.1 无锁

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public class SyncTest {
    //测试锁
    final Object lock = new Object();
    //获取pthread  tid
    JniTool jniTool = new JniTool();

    public static void main(String[] args) throws InterruptedException {
        //不打开，默认就是无所的状态
        //Thread.sleep(5000);
        SyncTest test = new SyncTest();
        System.out.println("---------------------------start--------------------");
        test.start();
    }

    public void start() throws InterruptedException {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                int count = 0;
                System.out.println(Thread.currentThread().getName() + " start");
                while (true) {
                    if (count < 50) {
                        count++;
                    } else {
                        return;
                    }
                    try {
                        lock();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        };
        new Thread(runnable).start();
    }
    public void lock() throws InterruptedException {
        synchronized (lock) {
            jniTool.getThreadID();
        }
    }
}

out.log

  • 通过log可以看到50次调用,通过搜索tid查看

  • 刚开始和结束调用了系统锁，中间是没有调用系统锁

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    3545: pthread_mutex_lock log  PID = 399 TID = 140058569967360 mutex=0x7f61e800b728 
      3546: pthread_mutex_lock log  PID = 399 TID = 140058569967360 mutex=0x7f61e8100b28 
      3549: pthread_mutex_lock log  PID = 399 TID = 140058569967360 mutex=0x7f61e8100b28 
      3555: pthread_mutex_lock log  PID = 399 TID = 140058569967360 mutex=0x7f61e80b9228 
      3562: pthread_mutex_lock log  PID = 399 TID = 140058569967360 mutex=0x7f61f778b8a0 
      3563: pthread_mutex_lock log  PID = 399 TID = 140058569967360 mutex=0x7f61f83d3948 
      3564: java_lock log-----------PID = 399 TID = 140058569967360 
      3575: java_lock log-----------PID = 399 TID = 140058569967360 
      3576: java_lock log-----------PID = 399 TID = 140058569967360 
      3577: java_lock log-----------PID = 399 TID = 140058569967360 
      3578: java_lock log-----------PID = 399 TID = 140058569967360 
      3579: java_lock log-----------PID = 399 TID = 140058569967360 
      3580: java_lock log-----------PID = 399 TID = 140058569967360 
      3581: java_lock log-----------PID = 399 TID = 140058569967360 
      3582: java_lock log-----------PID = 399 TID = 140058569967360 
      3583: java_lock log-----------PID = 399 TID = 140058569967360 
      3584: java_lock log-----------PID = 399 TID = 140058569967360 
      3585: java_lock log-----------PID = 399 TID = 140058569967360 
      3586: java_lock log-----------PID = 399 TID = 140058569967360 
      3587: java_lock log-----------PID = 399 TID = 140058569967360 
      3588: java_lock log-----------PID = 399 TID = 140058569967360 
      3590: java_lock log-----------PID = 399 TID = 140058569967360 
      3591: java_lock log-----------PID = 399 TID = 140058569967360 
      3592: java_lock log-----------PID = 399 TID = 140058569967360 
      3593: java_lock log-----------PID = 399 TID = 140058569967360 
      3594: java_lock log-----------PID = 399 TID = 140058569967360 
      3595: java_lock log-----------PID = 399 TID = 140058569967360 
      3596: java_lock log-----------PID = 399 TID = 140058569967360 
      3597: java_lock log-----------PID = 399 TID = 140058569967360 
      3598: java_lock log-----------PID = 399 TID = 140058569967360 
      3599: java_lock log-----------PID = 399 TID = 140058569967360 
      3600: java_lock log-----------PID = 399 TID = 140058569967360 
      3601: java_lock log-----------PID = 399 TID = 140058569967360 
      3602: java_lock log-----------PID = 399 TID = 140058569967360 
      3603: java_lock log-----------PID = 399 TID = 140058569967360 
      3604: java_lock log-----------PID = 399 TID = 140058569967360 
      3605: java_lock log-----------PID = 399 TID = 140058569967360 
      3606: java_lock log-----------PID = 399 TID = 140058569967360 
      3607: java_lock log-----------PID = 399 TID = 140058569967360 
      3608: java_lock log-----------PID = 399 TID = 140058569967360 
      3609: java_lock log-----------PID = 399 TID = 140058569967360 
      3610: java_lock log-----------PID = 399 TID = 140058569967360 
      3611: java_lock log-----------PID = 399 TID = 140058569967360 
      3612: java_lock log-----------PID = 399 TID = 140058569967360 
      3613: java_lock log-----------PID = 399 TID = 140058569967360 
      3614: java_lock log-----------PID = 399 TID = 140058569967360 
      3615: java_lock log-----------PID = 399 TID = 140058569967360 
      3616: java_lock log-----------PID = 399 TID = 140058569967360 
      3617: java_lock log-----------PID = 399 TID = 140058569967360 
      3618: java_lock log-----------PID = 399 TID = 140058569967360 
      3619: java_lock log-----------PID = 399 TID = 140058569967360 
      3620: java_lock log-----------PID = 399 TID = 140058569967360 
      3621: java_lock log-----------PID = 399 TID = 140058569967360 
      3622: java_lock log-----------PID = 399 TID = 140058569967360 
      3623: java_lock log-----------PID = 399 TID = 140058569967360 
      3624: pthread_mutex_lock log  PID = 399 TID = 140058569967360 mutex=0x7f61e800b528 
      3625: pthread_mutex_lock log  PID = 399 TID = 140058569967360 mutex=0x7f61f77a32c0 
      3626: pthread_mutex_lock log  PID = 399 TID = 140058569967360 mutex=0x7f61f77a32c0

    6.2 偏向锁

  • 偏向锁是默认延时加载的

  • 我们可以加JVM参数或sleep

  • 通过上面的代码，加上 Thread.sleep(5000);确保偏向锁打开


    out.log

  • 查看输出, 效果如上

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    3742: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25c800b728 
      3743: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25c80e9128 
      3750: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25c80e9128 
      3752: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25c80b9228 
      3763: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25cffe18a0 
      3764: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25d4c8b948 
      3765: java_lock log-----------PID = 431 TID = 139799890413312 
      3772: java_lock log-----------PID = 431 TID = 139799890413312 
      3773: java_lock log-----------PID = 431 TID = 139799890413312 
      3774: java_lock log-----------PID = 431 TID = 139799890413312 
      3775: java_lock log-----------PID = 431 TID = 139799890413312 
      3776: java_lock log-----------PID = 431 TID = 139799890413312 
      3777: java_lock log-----------PID = 431 TID = 139799890413312 
      3778: java_lock log-----------PID = 431 TID = 139799890413312 
      3779: java_lock log-----------PID = 431 TID = 139799890413312 
      3780: java_lock log-----------PID = 431 TID = 139799890413312 
      3781: java_lock log-----------PID = 431 TID = 139799890413312 
      3782: java_lock log-----------PID = 431 TID = 139799890413312 
      3783: java_lock log-----------PID = 431 TID = 139799890413312 
      3785: java_lock log-----------PID = 431 TID = 139799890413312 
      3787: java_lock log-----------PID = 431 TID = 139799890413312 
      3788: java_lock log-----------PID = 431 TID = 139799890413312 
      3789: java_lock log-----------PID = 431 TID = 139799890413312 
      3790: java_lock log-----------PID = 431 TID = 139799890413312 
      3791: java_lock log-----------PID = 431 TID = 139799890413312 
      3792: java_lock log-----------PID = 431 TID = 139799890413312 
      3793: java_lock log-----------PID = 431 TID = 139799890413312 
      3794: java_lock log-----------PID = 431 TID = 139799890413312 
      3795: java_lock log-----------PID = 431 TID = 139799890413312 
      3796: java_lock log-----------PID = 431 TID = 139799890413312 
      3797: java_lock log-----------PID = 431 TID = 139799890413312 
      3798: java_lock log-----------PID = 431 TID = 139799890413312 
      3799: java_lock log-----------PID = 431 TID = 139799890413312 
      3800: java_lock log-----------PID = 431 TID = 139799890413312 
      3801: java_lock log-----------PID = 431 TID = 139799890413312 
      3802: java_lock log-----------PID = 431 TID = 139799890413312 
      3803: java_lock log-----------PID = 431 TID = 139799890413312 
      3804: java_lock log-----------PID = 431 TID = 139799890413312 
      3805: java_lock log-----------PID = 431 TID = 139799890413312 
      3806: java_lock log-----------PID = 431 TID = 139799890413312 
      3807: java_lock log-----------PID = 431 TID = 139799890413312 
      3808: java_lock log-----------PID = 431 TID = 139799890413312 
      3809: java_lock log-----------PID = 431 TID = 139799890413312 
      3810: java_lock log-----------PID = 431 TID = 139799890413312 
      3811: java_lock log-----------PID = 431 TID = 139799890413312 
      3812: java_lock log-----------PID = 431 TID = 139799890413312 
      3813: java_lock log-----------PID = 431 TID = 139799890413312 
      3814: java_lock log-----------PID = 431 TID = 139799890413312 
      3815: java_lock log-----------PID = 431 TID = 139799890413312 
      3816: java_lock log-----------PID = 431 TID = 139799890413312 
      3817: java_lock log-----------PID = 431 TID = 139799890413312 
      3818: java_lock log-----------PID = 431 TID = 139799890413312 
      3819: java_lock log-----------PID = 431 TID = 139799890413312 
      3820: java_lock log-----------PID = 431 TID = 139799890413312 
      3821: java_lock log-----------PID = 431 TID = 139799890413312 
      3822: java_lock log-----------PID = 431 TID = 139799890413312 
      3823: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25c8079528 
      3824: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25c80e9128 
      3828: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25c80e9128 
      3829: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25c800b528 
      3830: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25cfff92c0 
      3831: pthread_mutex_lock log  PID = 431 TID = 139799890413312 mutex=0x7f25cfff92c0

6.3 轻量级锁

  • 我们偏向锁，升级到轻量级锁
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    public class SyncTest {
        //测试锁
        final Object lock = new Object();
        //获取pthread  tid
        JniTool jniTool = new JniTool();

        public static void main(String[] args) throws InterruptedException {
            //打开就是默认的偏向锁，默认是可偏向状态，但是不偏向任何一个线程
            //不打开，默认就是无所的状态
            Thread.sleep(5000);
            SyncTest test = new SyncTest();
            // test.parseHeaderInfo((ClassLayout.parseInstance(test.lock).toPrintable()));
            System.out.println("---------------------------start--------------------");
            test.start();
        }

        public void start() throws InterruptedException {
            Runnable runnable = new Runnable() {
                @Override
                public void run() {
                    int count = 0;
                    System.out.println(Thread.currentThread().getName() + " start");
                    while (true) {
                        if (count < 50) {
                            count++;
                        } else {
                        //若线程没有结束，但是线程1放锁了，升级为轻量级锁
                           try {
                               Thread.sleep(100000);
                           } catch (InterruptedException e) {
                               e.printStackTrace();
                           }
                            return;
                        }
                        try {
                            lock();
                            // parseHeaderInfo(ClassLayout.parseInstance(lock).toPrintable());
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            };
            new Thread(runnable).start();
            //加上，保证线程1结束，若果线程1已经结束，则还是偏向锁
            //若线程没有结束，但是线程1放锁了，升级为轻量级锁
            Thread.sleep(2000);
            //不加,则会升级为重量级锁
           new Thread(runnable).start();
        }
        public void lock() throws InterruptedException {
            synchronized (lock) {
                jniTool.getThreadID();
            }
        }
    }
  • out.log
  • 线程1的时候偏向
  • 线程2的时候，升级到轻量级锁
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    3763: pthread_mutex_lock log  PID = 498 TID = 139928822331136 mutex=0x7f43cc00b728 
      3764: pthread_mutex_lock log  PID = 498 TID = 139928822331136 mutex=0x7f43cc108d28 
      3768: pthread_mutex_lock log  PID = 498 TID = 139928822331136 mutex=0x7f43cc108d28 
      3769: pthread_mutex_lock log  PID = 498 TID = 139928822331136 mutex=0x7f43cc0bba28 
      3774: pthread_mutex_lock log  PID = 498 TID = 139928822331136 mutex=0x7f43d3fe18a0 
      3775: pthread_mutex_lock log  PID = 498 TID = 139928822331136 mutex=0x7f43d9bea948 
      3777: java_lock log-----------PID = 498 TID = 139928822331136 
      3789: java_lock log-----------PID = 498 TID = 139928822331136 
      3790: java_lock log-----------PID = 498 TID = 139928822331136 
      3791: java_lock log-----------PID = 498 TID = 139928822331136 
      3792: java_lock log-----------PID = 498 TID = 139928822331136 
      3793: java_lock log-----------PID = 498 TID = 139928822331136 
      3794: java_lock log-----------PID = 498 TID = 139928822331136 
      3795: java_lock log-----------PID = 498 TID = 139928822331136 
      3796: java_lock log-----------PID = 498 TID = 139928822331136 
      3797: java_lock log-----------PID = 498 TID = 139928822331136 
      3798: java_lock log-----------PID = 498 TID = 139928822331136 
      3799: java_lock log-----------PID = 498 TID = 139928822331136 
      3800: java_lock log-----------PID = 498 TID = 139928822331136 
      3801: java_lock log-----------PID = 498 TID = 139928822331136 
      3802: java_lock log-----------PID = 498 TID = 139928822331136 
      3803: java_lock log-----------PID = 498 TID = 139928822331136 
      3804: java_lock log-----------PID = 498 TID = 139928822331136 
      3805: java_lock log-----------PID = 498 TID = 139928822331136 
      3806: java_lock log-----------PID = 498 TID = 139928822331136 
      3807: java_lock log-----------PID = 498 TID = 139928822331136 
      3808: java_lock log-----------PID = 498 TID = 139928822331136 
      3809: java_lock log-----------PID = 498 TID = 139928822331136 
      3810: java_lock log-----------PID = 498 TID = 139928822331136 
      3811: java_lock log-----------PID = 498 TID = 139928822331136 
      3812: java_lock log-----------PID = 498 TID = 139928822331136 
      3813: java_lock log-----------PID = 498 TID = 139928822331136 
      3814: java_lock log-----------PID = 498 TID = 139928822331136 
      3815: java_lock log-----------PID = 498 TID = 139928822331136 
      3816: java_lock log-----------PID = 498 TID = 139928822331136 
      3817: java_lock log-----------PID = 498 TID = 139928822331136 
      3818: java_lock log-----------PID = 498 TID = 139928822331136 
      3819: java_lock log-----------PID = 498 TID = 139928822331136 
      3820: java_lock log-----------PID = 498 TID = 139928822331136 
      3822: java_lock log-----------PID = 498 TID = 139928822331136 
      3824: java_lock log-----------PID = 498 TID = 139928822331136 
      3825: java_lock log-----------PID = 498 TID = 139928822331136 
      3826: java_lock log-----------PID = 498 TID = 139928822331136 
      3827: java_lock log-----------PID = 498 TID = 139928822331136 
      3828: java_lock log-----------PID = 498 TID = 139928822331136 
      3829: java_lock log-----------PID = 498 TID = 139928822331136 
      3830: java_lock log-----------PID = 498 TID = 139928822331136 
      3831: java_lock log-----------PID = 498 TID = 139928822331136 
      3832: java_lock log-----------PID = 498 TID = 139928822331136 
      3833: java_lock log-----------PID = 498 TID = 139928822331136 
      3834: java_lock log-----------PID = 498 TID = 139928822331136 
      3835: java_lock log-----------PID = 498 TID = 139928822331136 
      3836: java_lock log-----------PID = 498 TID = 139928822331136 
      3837: java_lock log-----------PID = 498 TID = 139928822331136 
      3838: java_lock log-----------PID = 498 TID = 139928822331136 
      3839: java_lock log-----------PID = 498 TID = 139928822331136 
      3840: pthread_mutex_lock log  PID = 498 TID = 139928822331136 mutex=0x7f43cc108b28 
      3932: pthread_mutex_lock log  PID = 498 TID = 139928821278464 mutex=0x7f43cc00b728 
      3933: pthread_mutex_lock log  PID = 498 TID = 139928821278464 mutex=0x7f43cc0dd228 
      3938: pthread_mutex_lock log  PID = 498 TID = 139928821278464 mutex=0x7f43cc0dd228 
      3942: pthread_mutex_lock log  PID = 498 TID = 139928821278464 mutex=0x7f43cc079528 
      3945: pthread_mutex_lock log  PID = 498 TID = 139928821278464 mutex=0x7f43cc079528 
      3950: pthread_mutex_lock log  PID = 498 TID = 139928821278464 mutex=0x7f43cc079528 
      3953: java_lock log-----------PID = 498 TID = 139928821278464 
      3954: java_lock log-----------PID = 498 TID = 139928821278464 
      3955: java_lock log-----------PID = 498 TID = 139928821278464 
      3956: java_lock log-----------PID = 498 TID = 139928821278464 
      3957: java_lock log-----------PID = 498 TID = 139928821278464 
      3958: java_lock log-----------PID = 498 TID = 139928821278464 
      3959: java_lock log-----------PID = 498 TID = 139928821278464 
      3960: java_lock log-----------PID = 498 TID = 139928821278464 
      3961: java_lock log-----------PID = 498 TID = 139928821278464 
      3962: java_lock log-----------PID = 498 TID = 139928821278464 
      3963: java_lock log-----------PID = 498 TID = 139928821278464 
      3964: java_lock log-----------PID = 498 TID = 139928821278464 
      3965: java_lock log-----------PID = 498 TID = 139928821278464 
      3966: java_lock log-----------PID = 498 TID = 139928821278464 
      3967: java_lock log-----------PID = 498 TID = 139928821278464 
      3968: java_lock log-----------PID = 498 TID = 139928821278464 
      3969: java_lock log-----------PID = 498 TID = 139928821278464 
      3970: java_lock log-----------PID = 498 TID = 139928821278464 
      3971: java_lock log-----------PID = 498 TID = 139928821278464 
      3972: java_lock log-----------PID = 498 TID = 139928821278464 
      3973: java_lock log-----------PID = 498 TID = 139928821278464 
      3974: java_lock log-----------PID = 498 TID = 139928821278464 
      3975: java_lock log-----------PID = 498 TID = 139928821278464 
      3976: java_lock log-----------PID = 498 TID = 139928821278464 
      3977: java_lock log-----------PID = 498 TID = 139928821278464 
      3978: java_lock log-----------PID = 498 TID = 139928821278464 
      3979: java_lock log-----------PID = 498 TID = 139928821278464 
      3980: java_lock log-----------PID = 498 TID = 139928821278464 
      3981: java_lock log-----------PID = 498 TID = 139928821278464 
      3982: java_lock log-----------PID = 498 TID = 139928821278464 
      3983: java_lock log-----------PID = 498 TID = 139928821278464 
      3984: java_lock log-----------PID = 498 TID = 139928821278464 
      3985: java_lock log-----------PID = 498 TID = 139928821278464 
      3986: java_lock log-----------PID = 498 TID = 139928821278464 
      3987: java_lock log-----------PID = 498 TID = 139928821278464 
      3988: java_lock log-----------PID = 498 TID = 139928821278464 
      3989: java_lock log-----------PID = 498 TID = 139928821278464 
      3990: java_lock log-----------PID = 498 TID = 139928821278464 
      3991: java_lock log-----------PID = 498 TID = 139928821278464 
      3992: java_lock log-----------PID = 498 TID = 139928821278464 
      3993: java_lock log-----------PID = 498 TID = 139928821278464 
      3994: java_lock log-----------PID = 498 TID = 139928821278464 
      3995: java_lock log-----------PID = 498 TID = 139928821278464 
      3996: java_lock log-----------PID = 498 TID = 139928821278464 
      3997: java_lock log-----------PID = 498 TID = 139928821278464 
      3998: java_lock log-----------PID = 498 TID = 139928821278464 
      3999: java_lock log-----------PID = 498 TID = 139928821278464 
      4000: java_lock log-----------PID = 498 TID = 139928821278464 
      4001: java_lock log-----------PID = 498 TID = 139928821278464 
      4002: java_lock log-----------PID = 498 TID = 139928821278464 
      4003: pthread_mutex_lock log  PID = 498 TID = 139928821278464 mutex=0x7f43cc0dd028

6.4 重量级锁

  • 上面的代码，我们2个线程不等待，直接启动
  • 则会再偏向锁的情况下，直接升级到重量级锁

out.log

  • 可以明显看到 系统锁的调用测试变多

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    3750: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029000b728 
      3751: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f0290108c28 
      3756: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f0290108c28 
      3758: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029000b728 
      3759: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f02900b9228 
      3760: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a528 
      3770: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a528 
      3775: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029d4b28a0 
      3776: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029e0fa948 
      3778: java_lock log-----------PID = 532 TID = 139648716183296 
      3784: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f0290079528 
      3785: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a528 
      3796: java_lock log-----------PID = 532 TID = 139648716183296 
      3797: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a528 
      3798: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3799: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3800: java_lock log-----------PID = 532 TID = 139648716183296 
      3801: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3802: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3803: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3804: java_lock log-----------PID = 532 TID = 139648716183296 
      3805: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3806: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3807: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3808: java_lock log-----------PID = 532 TID = 139648716183296 
      3809: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3810: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3811: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3812: java_lock log-----------PID = 532 TID = 139648716183296 
      3813: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3814: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3815: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3816: java_lock log-----------PID = 532 TID = 139648716183296 
      3817: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3818: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3819: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3820: java_lock log-----------PID = 532 TID = 139648716183296 
      3821: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3822: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3823: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3824: java_lock log-----------PID = 532 TID = 139648716183296 
      3825: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3826: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3827: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3828: java_lock log-----------PID = 532 TID = 139648716183296 
      3829: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3830: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3831: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3832: java_lock log-----------PID = 532 TID = 139648716183296 
      3833: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3834: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3835: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3836: java_lock log-----------PID = 532 TID = 139648716183296 
      3837: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3838: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3839: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3840: java_lock log-----------PID = 532 TID = 139648716183296 
      3841: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3842: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3843: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3844: java_lock log-----------PID = 532 TID = 139648716183296 
      3845: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3846: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3847: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3848: java_lock log-----------PID = 532 TID = 139648716183296 
      3849: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3850: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3851: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3852: java_lock log-----------PID = 532 TID = 139648716183296 
      3853: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3854: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3855: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3856: java_lock log-----------PID = 532 TID = 139648716183296 
      3857: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3858: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3859: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3860: java_lock log-----------PID = 532 TID = 139648716183296 
      3861: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3862: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3863: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3864: java_lock log-----------PID = 532 TID = 139648716183296 
      3865: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3866: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3867: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3868: java_lock log-----------PID = 532 TID = 139648716183296 
      3869: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3870: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3871: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3872: java_lock log-----------PID = 532 TID = 139648716183296 
      3873: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3874: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3875: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3876: java_lock log-----------PID = 532 TID = 139648716183296 
      3877: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3878: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3879: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3880: java_lock log-----------PID = 532 TID = 139648716183296 
      3881: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3882: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3883: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3884: java_lock log-----------PID = 532 TID = 139648716183296 
      3885: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3886: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3887: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3888: java_lock log-----------PID = 532 TID = 139648716183296 
      3889: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3890: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3891: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3892: java_lock log-----------PID = 532 TID = 139648716183296 
      3893: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3894: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3895: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3896: java_lock log-----------PID = 532 TID = 139648716183296 
      3897: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3898: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3899: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3900: java_lock log-----------PID = 532 TID = 139648716183296 
      3901: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3902: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3903: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3904: java_lock log-----------PID = 532 TID = 139648716183296 
      3905: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3906: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3907: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3908: java_lock log-----------PID = 532 TID = 139648716183296 
      3909: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3910: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3911: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3912: java_lock log-----------PID = 532 TID = 139648716183296 
      3913: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3914: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3915: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3916: java_lock log-----------PID = 532 TID = 139648716183296 
      3917: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3918: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3919: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3920: java_lock log-----------PID = 532 TID = 139648716183296 
      3921: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3922: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3923: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3924: java_lock log-----------PID = 532 TID = 139648716183296 
      3925: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3926: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3927: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3928: java_lock log-----------PID = 532 TID = 139648716183296 
      3929: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3930: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3931: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3932: java_lock log-----------PID = 532 TID = 139648716183296 
      3933: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3934: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3935: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3936: java_lock log-----------PID = 532 TID = 139648716183296 
      3937: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3938: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3939: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3940: java_lock log-----------PID = 532 TID = 139648716183296 
      3941: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3942: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3943: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3944: java_lock log-----------PID = 532 TID = 139648716183296 
      3945: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3946: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3947: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3948: java_lock log-----------PID = 532 TID = 139648716183296 
      3949: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3950: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3951: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3952: java_lock log-----------PID = 532 TID = 139648716183296 
      3953: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3954: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3955: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3956: java_lock log-----------PID = 532 TID = 139648716183296 
      3957: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3958: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3959: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3960: java_lock log-----------PID = 532 TID = 139648716183296 
      3961: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3962: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3963: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3964: java_lock log-----------PID = 532 TID = 139648716183296 
      3965: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3966: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3967: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3968: java_lock log-----------PID = 532 TID = 139648716183296 
      3969: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3970: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3971: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3972: java_lock log-----------PID = 532 TID = 139648716183296 
      3973: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3974: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3975: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3976: java_lock log-----------PID = 532 TID = 139648716183296 
      3977: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3978: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3979: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3980: java_lock log-----------PID = 532 TID = 139648716183296 
      3981: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3982: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3983: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3984: java_lock log-----------PID = 532 TID = 139648716183296 
      3985: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3986: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3987: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3988: java_lock log-----------PID = 532 TID = 139648716183296 
      3989: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3990: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3991: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f029010a128 
      3992: pthread_mutex_lock log  PID = 532 TID = 139648716183296 mutex=0x7f0290108a28 
      3993: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a128 
      3994: java_lock log-----------PID = 532 TID = 139648647034624 
      3995: java_lock log-----------PID = 532 TID = 139648647034624 
      3996: java_lock log-----------PID = 532 TID = 139648647034624 
      3997: java_lock log-----------PID = 532 TID = 139648647034624 
      3998: java_lock log-----------PID = 532 TID = 139648647034624 
      3999: java_lock log-----------PID = 532 TID = 139648647034624 
      4000: java_lock log-----------PID = 532 TID = 139648647034624 
      4001: java_lock log-----------PID = 532 TID = 139648647034624 
      4002: java_lock log-----------PID = 532 TID = 139648647034624 
      4003: java_lock log-----------PID = 532 TID = 139648647034624 
      4004: java_lock log-----------PID = 532 TID = 139648647034624 
      4005: java_lock log-----------PID = 532 TID = 139648647034624 
      4006: java_lock log-----------PID = 532 TID = 139648647034624 
      4007: java_lock log-----------PID = 532 TID = 139648647034624 
      4008: java_lock log-----------PID = 532 TID = 139648647034624 
      4009: java_lock log-----------PID = 532 TID = 139648647034624 
      4010: java_lock log-----------PID = 532 TID = 139648647034624 
      4011: java_lock log-----------PID = 532 TID = 139648647034624 
      4012: java_lock log-----------PID = 532 TID = 139648647034624 
      4013: java_lock log-----------PID = 532 TID = 139648647034624 
      4014: java_lock log-----------PID = 532 TID = 139648647034624 
      4015: java_lock log-----------PID = 532 TID = 139648647034624 
      4016: java_lock log-----------PID = 532 TID = 139648647034624 
      4017: java_lock log-----------PID = 532 TID = 139648647034624 
      4018: java_lock log-----------PID = 532 TID = 139648647034624 
      4019: java_lock log-----------PID = 532 TID = 139648647034624 
      4020: java_lock log-----------PID = 532 TID = 139648647034624 
      4021: java_lock log-----------PID = 532 TID = 139648647034624 
      4022: java_lock log-----------PID = 532 TID = 139648647034624 
      4023: java_lock log-----------PID = 532 TID = 139648647034624 
      4024: java_lock log-----------PID = 532 TID = 139648647034624 
      4025: java_lock log-----------PID = 532 TID = 139648647034624 
      4026: java_lock log-----------PID = 532 TID = 139648647034624 
      4027: java_lock log-----------PID = 532 TID = 139648647034624 
      4028: java_lock log-----------PID = 532 TID = 139648647034624 
      4029: java_lock log-----------PID = 532 TID = 139648647034624 
      4030: java_lock log-----------PID = 532 TID = 139648647034624 
      4031: java_lock log-----------PID = 532 TID = 139648647034624 
      4032: java_lock log-----------PID = 532 TID = 139648647034624 
      4033: java_lock log-----------PID = 532 TID = 139648647034624 
      4034: java_lock log-----------PID = 532 TID = 139648647034624 
      4035: java_lock log-----------PID = 532 TID = 139648647034624 
      4036: java_lock log-----------PID = 532 TID = 139648647034624 
      4037: java_lock log-----------PID = 532 TID = 139648647034624 
      4038: java_lock log-----------PID = 532 TID = 139648647034624 
      4039: java_lock log-----------PID = 532 TID = 139648647034624 
      4040: java_lock log-----------PID = 532 TID = 139648647034624 
      4041: java_lock log-----------PID = 532 TID = 139648647034624 
      4042: java_lock log-----------PID = 532 TID = 139648647034624 
      4043: java_lock log-----------PID = 532 TID = 139648647034624 
      4044: pthread_mutex_lock log  PID = 532 TID = 139648647034624 mutex=0x7f029010a328

    7 总结

  • 无锁，偏向锁，轻量级锁，本质上都JVM层面的锁，除了开始和结束的时候，没有调用系统锁。

  • 重量级锁是需要 系统锁 pthread_mutex_lock 支持的

  • 每个线程50次调用，系统锁的调用次数，我们包括开始和结束

无锁 偏向 轻量级 重量级
线程数量 1 1 2 2
pthread_mutex_lock 调用次数 12 次 12次 14 次 161次
  • 对比 轻量级锁和 重量级锁还是 优化比较大的

8 docker 镜像

如果有需要, 上面

  • docker pull registry.cn-hangzhou.aliyuncs.com/kaiattrib/test:ubuntu16_glibc23
  • 带 jdk
  • 带 glibc23 源码，可编译
  • 带 自己写的一个jni调用库
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