java应用排查高线程

java占用线程高的排查方法

解压arthas

启动案例程序

bash 复制代码

nohup java -jar math-game.jar > 1.txt 2>&1 &

展示当前最繁忙的 5 个线程，并按 CPU 占用率从高到低排序

bash 复制代码

java -jar arthas-boot.jar

[arthas@6028]$ thread -n 5 
"arthas-command-execute" Id=22 cpuUsage=0.25% deltaTime=0ms time=3ms RUNNABLE
    at sun.management.ThreadImpl.dumpThreads0(Native Method)
    at sun.management.ThreadImpl.getThreadInfo(ThreadImpl.java:448)
    at com.taobao.arthas.core.command.monitor200.ThreadCommand.processTopBusyThreads(ThreadCommand.java:206)
    at com.taobao.arthas.core.command.monitor200.ThreadCommand.process(ThreadCommand.java:122)
    at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl.process(AnnotatedCommandImpl.java:82)
    at com.taobao.arthas.core.shell.command.impl.AnnotatedCommandImpl.access$100(AnnotatedCommandImpl.java:18)

抓取火焰图10秒

bash 复制代码

[arthas@6028]$ profiler start --duration 10
Profiling started
profiler will silent stop after 10 seconds.
profiler output file will be: /root/arthas-output/20260610-190020.html

# 抓10s火焰图并指定位置输出
[arthas@2527]$ profiler start -d 10 -f /root/hyt/myhyt10s.html 
Profiling started
profiler will silent stop after 10 seconds.
profiler output file will be: /root/hyt/myhyt10s.html

手动抓火焰图

bash 复制代码

[arthas@2527]$ profiler start 
Profiling started

[arthas@2527]$ profiler status 
Profiling is running for 6 seconds

[arthas@2527]$ profiler stop
OK
profiler output file: /root/art/arthas-output/20260613-165656.html

# 指定目录停止
profiler stop -f /root/hyt/myhyt.html

使用arthas保存当前的dump

bash 复制代码

[arthas@2527]$ heapdump 
Dumping heap to /tmp/heapdump2026-06-13-17-154000252027065352381.hprof ...
Heap dump file created

指定生成的目录

bash 复制代码

[arthas@2527]$ heapdump /home/admin/dumps/myapp-2024.hprof
Dumping heap to /home/admin/dumps/myapp-2024.hprof ...
Heap dump file created

jmap 保存当时内存快照

bash 复制代码

[root@localhost ~]# ps -ef | grep java 
root       2527   1899  0 16:50 pts/0    00:00:05 java -jar math-game.jar
root       4923   4560  0 17:24 pts/1    00:00:00 grep --color=auto java
[root@localhost ~]# jmap -dump:format=b,file=/tmp/heap.hprof 2527 
Dumping heap to /tmp/heap.hprof ...
Heap dump file created

jstack 打印指定java进程的堆栈

bash 复制代码

# 打印线程堆栈（会输出所有线程）
jstack <pid>

# 打印锁信息（包括死锁检测）
jstack -l <pid>

# 如果进程无响应，强制打印（通常用于 -F 参数）
jstack -F <pid>

打印JVM 的堆栈信息，以供问题排查

bash 复制代码

[root@localhost art]# ps -ef | grep java 
root       2527   1899  0 16:50 pts/0    00:00:00 java -jar math-game.jar
root       2770   1899  0 16:52 pts/0    00:00:00 grep --color=auto java

[root@localhost.com ~]# jstack -F 2527 > /tmp/jstack1.log
[root@localhost.com ~]# jstack 2527 > /tmp/jstack2.log

Tomcat底层是通过JVM运行的，JVM在操作系统中是作为一个进程存在的，而java中的所有线程是在VM进程中运行的，同时cPU调度的是进程中的线程。那么，要查看java是否支持多线程，是体现在操作系统中的，我们可以查看java进程是否可以使用CPU的多核资源。如果可以，那么java就是支持多线程的，而支持多线程的话，java进程占用CPU资源300%以上是完全可能的。

使用jstack工具将进程信息打印输出

jstack是java虚拟机自带的一种堆栈跟踪工具。可以用于生成java虚拟机当前时刻的线程快照。线程快照是当前java虚拟机内每一条线程正在执行的方法堆栈的集合,生成线程快照的主要目的是定位线程出现长时间停顿的原因，如线程间死锁、死循环、请求外部资源导致的长时间等待等。

想要通过jstack命令来分析线程的情况的话，首先要知道线程都有哪些状态，下面这些状态是我们使用istack命令查看线程堆栈信息时可能会看到的线程的几种状态

NEW,未启动的。不会出现在Dump中

RUNNABLE,在虚拟机内执行的运行中状态。

BLOCKED,受阻塞并等待监视器锁WATiNG,无限期等待另一个线程执行特定操作

TIMED_WATING,有时限的等待另一个线程的特定操作

TERMINATED,已退出的

案例分析

bash 复制代码

top
top -H -p 3994
printf '%x\n' 3995
jstack 3994 | grep f9b
     java进程的id   某线程的16进制

bash 复制代码

[root@localhost ~]# top 
top - 20:25:36 up  1:10,  3 users,  load average: 0.00, 0.01, 0.03
Tasks: 202 total,   2 running, 200 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.2 us,  0.2 sy,  0.0 ni, 99.5 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem :  4026160 total,  2875184 free,   700224 used,   450752 buff/cache
KiB Swap:  4063228 total,  4063228 free,        0 used.  3083524 avail Mem 

   PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                         
  3994 root      20   0 4210704 122736  14308 S   1.0  3.0   0:06.26 java                            
     1 root      20   0  191276   4216   2604 S   0.0  0.1   0:03.12 systemd                         
     2 root      20   0       0      0      0 S   0.0  0.0   0:00.01 kthreadd                        
     4 root       0 -20       0      0      0 S   0.0  0.0   0:00.00 kworker/0:0H                    
     6 root      20   0       0      0      0 S   0.0  0.0   0:00.06 ksoftirqd/0                     
     7 root      rt   0       0      0      0 S   0.0  0.0   0:00.11 migration/0                     
     8 root      20   0       0      0      0 S   0.0  0.0   0:00.00 rcu_bh                          
     9 root      20   0       0      0      0 S   0.0  0.0   0:00.76 rcu_sched                       
    10 root       0 -20       0      0      0 S   0.0  0.0   0:00.00 lru-add-drain                   
    11 root      rt   0       0      0      0 S   0.0  0.0   0:00.02 watchdog/0                      
    12 root      rt   0       0      0      0 S   0.0  0.0   0:00.01 watchdog/1                      
    13 root      rt   0       0      0      0 S   0.0  0.0   0:00.10 migration/1                     
[root@localhost ~]# top -H -p 3994
top - 20:25:42 up  1:10,  3 users,  load average: 0.00, 0.01, 0.03
Threads:  25 total,   0 running,  25 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem :  4026160 total,  2875804 free,   699604 used,   450752 buff/cache
KiB Swap:  4063228 total,  4063228 free,        0 used.  3084144 avail Mem 

   PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND                          
  3994 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.02 java                             
  3995 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.51 java                             
  3996 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.32 java                             
  3997 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.31 java                             
  3998 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.30 java                             
  3999 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.32 java                             
  4000 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.14 java                             
  4001 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.00 java                             
  4002 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.00 java                             
  4003 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.00 java                             
  4004 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.29 java                             
  4005 root      20   0 4210704 122736  14308 S  0.0  3.0   0:00.26 java                             
[root@localhost ~]# printf '%x\n' 3995
f9b

[root@localhost ~]# jstack 3994 | grep f9b 
"main" #1 prio=5 os_prio=0 tid=0x00007fd340008800 nid=0xf9b waiting on condition [0x00007fd346105000]

匹配该行及之后50行  -B是before 之前的50行
[root@localhost ~]# jstack 3994 | grep f9b -A 50
"main" #1 prio=5 os_prio=0 tid=0x00007fd340008800 nid=0xf9b waiting on condition [0x00007fd346105000]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
	at java.lang.Thread.sleep(Native Method)
	at java.lang.Thread.sleep(Thread.java:340)
	at java.util.concurrent.TimeUnit.sleep(TimeUnit.java:386)
	at demo.MathGame.main(MathGame.java:17)

"VM Thread" os_prio=0 tid=0x00007fd34013d800 nid=0xfa0 runnable 
"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007fd34001d800 nid=0xf9c runnable 
"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007fd34001f800 nid=0xf9d runnable 
"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00007fd340021800 nid=0xf9e runnable 
"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00007fd340023000 nid=0xf9f runnable 
"VM Periodic Task Thread" os_prio=0 tid=0x00007fd3401bb800 nid=0xfa8 waiting on condition 
JNI global references: 283