ASM-Booster-Thread原理解析 - 《Gradle开发笔记》

线程重命名，替换Thread
线程池优化
降低线程数量

该插件主要功能为多线程优化，首先需要先看看这个插件所支持的功能有什么

降低线程数量
线程重命名
线程池优化

线程重命名，替换Thread

原JAVA文件

class Test {
    void te(){
        new Thread(new Runnable() {
            @Override
            public void run() {
            }
        }).start();
    }
}

优化后的JAVA文件

class Test {
    Test() {
    }
    void te() {
        ShadowThread.setThreadName(
            new ShadowThread(new Runnable() {
                public void run() {
                }
            }, "\u200bnet.mikaelzero.myapplication.Test"),
            "\u200bnet.mikaelzero.myapplication.Test")
            .start();
    }
}

优化前的字节码指令

Compiled from "Test.java"
class net.mikaelzero.myapplication.Test {
  net.mikaelzero.myapplication.Test();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: return
  void te();
    Code:
       0: new           #2                  // class java/lang/Thread
       3: dup
       4: new           #3                  // class net/mikaelzero/myapplication/Test$1
       7: dup
       8: aload_0
       9: invokespecial #4                  // Method net/mikaelzero/myapplication/Test$1."<init>":(Lnet/mikaelzero/myapplication/Test;)V
      12: invokespecial #5                  // Method java/lang/Thread."<init>":(Ljava/lang/Runnable;)V
      15: invokevirtual #6                  // Method java/lang/Thread.start:()V
      18: return
}

优化后的字节码指令

Compiled from "Test.java"
class net.mikaelzero.myapplication.Test {
  net.mikaelzero.myapplication.Test();
    Code:
       0: aload_0
       1: invokespecial #11                 // Method java/lang/Object."<init>":()V
       4: return
  void te();
    Code:
       0: new           #16                 // class com/didiglobal/booster/instrument/ShadowThread
       3: dup
       4: new           #7                  // class net/mikaelzero/myapplication/Test$1
       7: dup
       8: aload_0
       9: invokespecial #19                 // Method net/mikaelzero/myapplication/Test$1."<init>":(Lnet/mikaelzero/myapplication/Test;)V
      12: ldc           #21                 // String net.mikaelzero.myapplication.Test
      14: invokespecial #24                 // Method com/didiglobal/booster/instrument/ShadowThread."<init>":(Ljava/lang/Runnable;Ljava/lang/String;)V
      17: ldc           #21                 // String net.mikaelzero.myapplication.Test
      19: invokestatic  #28                 // Method com/didiglobal/booster/instrument/ShadowThread.setThreadName:(Ljava/lang/Thread;Ljava/lang/String;)Ljava/lang/Thread;
      22: invokevirtual #33                 // Method java/lang/Thread.start:()V
      25: return
}

将Thread的全限定名替换为ShadowThread
将初始化Thread的指令（invokespecial）中的限定名替换为ShdowThread，且传入参数为String名称
调用ShadowThread.setThreadName，并传入字符串

    private fun TypeInsnNode.transformNew(@Suppress("UNUSED_PARAMETER") context: TransformContext, klass: ClassNode, method: MethodNode, type: String, optimizable: Boolean = false) {
        this.find {
            (it.opcode == Opcodes.INVOKESPECIAL) &&
                    (it is MethodInsnNode) &&
                    (this.desc == it.owner && "<init>" == it.name)
        }?.isInstanceOf { init: MethodInsnNode ->
            // 1
            this.desc = type
            //2
            val rp = init.desc.lastIndexOf(')')
            init.apply {
                owner = type
                desc = "${desc.substring(0, rp)}Ljava/lang/String;${if (optimizable) "Z" else ""}${desc.substring(rp)}"
            }
            //3
            method.instructions.insertBefore(init, LdcInsnNode(makeThreadName(klass.className)))
            if (optimizable) {
                method.instructions.insertBefore(init, LdcInsnNode(optimizationEnabled))
            }
        } ?: throw TransformException("`invokespecial $desc` not found: ${klass.name}.${method.name}${method.desc}")
    }

通过重新设置desc将Thread替换为ShadowThread,比如 java/lang/Thread => com/didiglobal/booster/instrument/ShadowThread
(10行到14行)替换构造参数的全限定名，比如net/mikaelzero/myapplication/Test$1.”“:(Lnet/mikaelzero/myapplication/Test;)V 替换为 com/didiglobal/booster/instrument/ShadowThread.”“:(Ljava/lang/Runnable;Ljava/lang/String;)V
因为ShadowThread多了一个String的参数，所以需要先插入一个字符串到构造函数的Instructions指令前面

从字节码可以看出，invokevirtual和invokespecial部分的desc都需要进行替换，比如

invokevirtual #33                 // Method java/lang/Thread.start:()V

需要替换为

invokevirtual #33                 // Method com/didiglobal/booster/instrument/ShadowThread.start:()V

如果原代码调用了setName,比如

thread.setName("hello")
17: ldc           #6                  // String helo name
19: invokevirtual #7                  // Method java/lang/Thread.setName:(Ljava/lang/String;)V

需要替换为

thread.setName(ShadowThread.makeThreadName("helo", "\u200bnet.mikaelzero.myapplication.Test"));
9 ldc #26 <helo name>
21 ldc #21 <net.mikaelzero.myapplication.Test>
23 invokestatic #30 <com/didiglobal/booster/instrument/ShadowThread.makeThreadName>
26 invokevirtual #36 <java/lang/Thread.setName>

对应源码为

"setName(Ljava/lang/String;)V" -> {
                    method.instructions.insertBefore(this, LdcInsnNode(makeThreadName(klass.className)))
                    method.instructions.insertBefore(this, MethodInsnNode(Opcodes.INVOKESTATIC, SHADOW_THREAD, "makeThreadName", "(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;", false))
                    logger.println(" + $SHADOW_THREAD.makeThreadName(Ljava/lang/String;Ljava/lang/String;) => ${this.owner}.${this.name}${this.desc}: ${klass.name}.${method.name}${method.desc}")
                    this.owner = THREAD
                }

线程池优化

比如newFixedThreadPool 替换为newOptimizedFixedThreadPool，主要还是和上面的处理类似，通过desc替换以及插入对应的String参数

"defaultThreadFactory" -> {
                        val r = this.desc.lastIndexOf(')')
                        val desc = "${this.desc.substring(0, r)}Ljava/lang/String;${this.desc.substring(r)}"
                        logger.println(" * ${this.owner}.${this.name}${this.desc} => $SHADOW_EXECUTORS.${this.name}$desc: ${klass.name}.${method.name}${method.desc}")
                        this.owner = SHADOW_EXECUTORS
                        this.desc = desc
                        method.instructions.insertBefore(this, LdcInsnNode(makeThreadName(klass.className)))
                    }

降低线程数量

这些都是在配置线程池的时候做一个替换为自己的 ShadowExecutors，通过如下代码进行设置

    public static ScheduledExecutorService newOptimizedSingleThreadScheduledExecutor(final String name) {
        final ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(1, new NamedThreadFactory(name));
        executor.setKeepAliveTime(DEFAULT_KEEP_ALIVE, TimeUnit.MILLISECONDS);
        executor.allowCoreThreadTimeOut(true);
        return executor;
    }
    public static ScheduledExecutorService newOptimizedSingleThreadScheduledExecutor(final ThreadFactory factory, final String name) {
        final ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(1, new NamedThreadFactory(factory, name));
        executor.setKeepAliveTime(DEFAULT_KEEP_ALIVE, TimeUnit.MILLISECONDS);
        executor.allowCoreThreadTimeOut(true);
        return executor;
    }

对于替换，和替换Thread的原理基本上是一致的。