如何定位消耗CPU最多的线程-白红宇

如何定位消耗CPU最多的线程

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发布时间：2019-06-22

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一般在进程中都是存在多个线程，然而有可能存在特别耗费CPU的线程，但是如何去定位它们呢，下面通过一段代码来看看

package demo;public class TestThreadCpu {	public static void main(String[] args) {		for(int i = 0; i < 10; i++){			new Thread(){				@Override				public void run() {										try {						Thread.sleep(1000);					} catch (InterruptedException e) {						// TODO Auto-generated catch block						e.printStackTrace();					}									}							}.start();		}				Thread t  = new Thread(){			@Override			public void run() {								int i = 0;				while(true){					i=(i++)/100;				}			}					};		t.setName("Busiest Thread");		t.start();	}}

这个例子里新建了 11个线程，其中10个线程没干啥，主要就是 sleep 另外一个线程循环的跑着，可以看出，这个单独的线程是当前进程里面最耗 CPU 的线程了。

下面我们怎么来将这个单独的线程抓出来呢？

首先我们通过 top -Hp <pid> 来看这个进程里所有的线程CPU消耗情况，得到如下数据

$ top -Hp 18207top - 19:11:43 up 573 days,  2:43,  2 users,  load average: 3.03, 3.03, 3.02Tasks:  44 total,   1 running,  43 sleeping,   0 stopped,   0 zombieCpu(s): 18.8%us,  0.0%sy,  0.0%ni, 81.1%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%stMem:  99191752k total, 98683576k used,   508176k free,   128248k buffersSwap:  1999864k total,   191064k used,  1808800k free, 17413760k cached  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND18250 admin     20   0 26.1g  28m  10m R 99.9  0.0   0:19.50 java TestThreadCpu 18207 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18208 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.09 java TestThreadCpu 18209 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18210 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18211 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18212 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18213 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18214 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18215 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18216 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18217 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18218 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18219 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18220 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18221 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18222 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18223 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18224 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18225 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18226 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 18227 admin     20   0 26.1g  28m  10m S  0.0  0.0   0:00.00 java TestThreadCpu 拿到这个结果之后，我们可以看到cpu最高的线程是pid为18250的线程，占了99.8%： PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND18250 admin     20   0 26.1g  28m  10m R 99.9  0.0   0:19.50 java TestThreadCpu

接下来我们可以通过 jstack <pid> 的输出来哥哥线程栈：

$ jstack 182072016-03-30 19:12:23Full thread dump OpenJDK 64-Bit Server VM (25.66-b60 mixed mode):"Attach Listener" #30 daemon prio=9 os_prio=0 tid=0x00007fb90be13000 nid=0x47d7 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"DestroyJavaVM" #29 prio=5 os_prio=0 tid=0x00007fb96245b800 nid=0x4720 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"Busiest Thread" #28 prio=5 os_prio=0 tid=0x00007fb91498d000 nid=0x474a runnable [0x00007fb9065fe000]   java.lang.Thread.State: RUNNABLE    at Test$2.run(Test.java:18)"Thread-9" #27 prio=5 os_prio=0 tid=0x00007fb91498c800 nid=0x4749 waiting on condition [0x00007fb906bfe000]   java.lang.Thread.State: TIMED_WAITING (sleeping)    at java.lang.Thread.sleep(Native Method)    at Test$1.run(Test.java:9)"Thread-8" #26 prio=5 os_prio=0 tid=0x00007fb91498b800 nid=0x4748 waiting on condition [0x00007fb906ffe000]   java.lang.Thread.State: TIMED_WAITING (sleeping)    at java.lang.Thread.sleep(Native Method)    at Test$1.run(Test.java:9)"Thread-7" #25 prio=5 os_prio=0 tid=0x00007fb91498b000 nid=0x4747 waiting on condition [0x00007fb9073fe000]   java.lang.Thread.State: TIMED_WAITING (sleeping)    at java.lang.Thread.sleep(Native Method)    at Test$1.run(Test.java:9)"Thread-6" #24 prio=5 os_prio=0 tid=0x00007fb91498a000 nid=0x4746 waiting on condition [0x00007fb9077fe000]   java.lang.Thread.State: TIMED_WAITING (sleeping)    at java.lang.Thread.sleep(Native Method)    at Test$1.run(Test.java:9)...

上面我们注意到 nid 的值就是我们的线程ID，它是16进制，我们最消耗 CPU 的最高的线程 18250，转化成 16进制 0x47A 然后从上面的线程栈里面找到 nid=0x47A 的线程，其栈为

"Busiest Thread" #28 prio=5 os_prio=0 tid=0x00007fb91498d000 nid=0x474a runnable [0x00007fb9065fe000]   java.lang.Thread.State: RUNNABLE    at Test$2.run(Test.java:18)

即将最耗CPU的线程找出来了，就是 Businest Thread

转载于:https://my.oschina.net/exit/blog/814548

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