Linux Load编程竞赛 �C 后端技术 by Tim Yang

Linux Load编程竞赛 �C 后端技术 by Tim Yang
Linux load average的意思就是说 目前有ready的进程 但是cpu都在满，然后这个数是一分钟的平均值。公式：loadvg = tasks running + tasks waiting (for cores) + tasks blocked. 让CPU满是最简单的方式
为了更好理解load average，Tim某天在群征集一段代码使load average最高。于是乎，群友纷纷出手。

Shell版

#!/bin/sh
for((i=0;i<10;i++));do
{
for((j=0;j<1000000000000;j++));do echo '1'>>1; done
}&
done

Ruby

ruby -e "require 'thread';t = Mutex.new;10.times {fork {10000000.times{t.synchronize {x=Time.now}}}}"

Java版本2

public class Test {

   public static void main(String[] args) {
       for (int i = 0; i < 1000; i++) {
           new Thread() {
               @Override
               public void run() {
                   while (true) ;
               }
           }.start();
       }
   }
}

Java版本3

写两类线程，一类进行lockObject wait, 一类进行lockObject notifyall。 cpu上下文切换消耗 竞争激烈。Load能很高。

public class LoadHighDemo {

   public static void main(String[] args) throws Exception {
       LoadHighDemo demo = new LoadHighDemo();
       demo.runTest();
   }

   private void runTest() throws Exception {
       Object[] locks = new Object[5000];
       for (int i = 0; i < 5000; i++) {
           locks[i] = new Object();
           new Thread(new WaitTask(locks[i])).start();
           new Thread(new NotifyTask(locks[i])).start();
       }
   }

   class WaitTask implements Runnable {

       private Object lockObject = null;

       public WaitTask(Object obj) {
           lockObject = obj;
       }

       public void run() {
           while (true) {
               try {
                   synchronized (lockObject) {
                       lockObject.wait(new java.util.Random().nextInt(10));
                   }
               } catch (Exception e) {;
               }
           }
       }
   }

   class NotifyTask implements Runnable {

       private Object lockObject = null;

       public NotifyTask(Object obj) {
           lockObject = obj;
       }

       public void run() {
           while (true) {
               synchronized (lockObject) {
                   lockObject.notifyAll();
               }
               try {
                   Thread.sleep(new java.util.Random().nextInt(5));
               } catch (InterruptedException e) {
               }
           }
       }
   }
}

Python版

把5分钟 load avg 稳定在1024了
在本群感到了一种情怀。。。

#!/usr/bin/env python
import os
import sys
import time

def load_add_1():
time.sleep(30)
fd=os.open("test.txt",os.O_CREAT|os.O_RDWR|os.O_SYNC, 0644)
for i in xrange(10000*100):
os.write(fd," "*100)
sys.exit(0)

for i in xrange(8192):
if os.fork() == 0:
load_add_1()

此版本将load跑到8192

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