The content of this article is about the method of troubleshooting the Java process CPU usage of 100%. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you. helped.
100% refers to occupying one core of the CPU, two cores is 200%, and so on.
CPU usage and corresponding process ID (pid) can be determined through the top command. On the top interface, press c (to display the complete command line parameters) and press 1 (to display the statistics of each core). (Recommended:Java Tutorial)
The most common possibilities for this problem are as follows:
1. Frequent Full GC caused by insufficient heap memory
can be solved by two methods: Command to confirm
sudo jmap -heap pid Check the heap memory consumption
sudo jstat -gc pid interval count Check the GC situation, example: sudo jstat -gc 5746 3000 5 means to check the 5746 process GC situation, print every 3000 milliseconds, print 5 times in total. If FGC/FGCT increases significantly, Full GC is very frequent.
Follow-up processing:
If the situation is urgent, you must restart the Java application process immediately. If it is not urgent, you need to obtain relevant information to analyze why the heap memory is consumed. There may be a memory leak problem. You can Use 1) sudo jmap -histo pid | head -n 20 to view the occupancy statistics of Java objects, 2) sudo jmap -dump:live,format=b,file=heap.bin pid to export the heap dump to a local file, you can Use the Eclipse MAT tool to analyze memory leaks
2. Code implementation issues
Idea: Track which thread is occupying the CPU, 1) First find the thread ID with high CPU usage in the local system, 2) Find the corresponding Java thread and thread stack
top -H -p pid to check which threads in a process occupy the CPU, copy the corresponding thread ID and convert it to hexadecimal [IDEA] Tools》Groovy Console》println Long.toHexString(1234) to complete the conversion].
sudo jstack -l -F pid | less Get the Java thread stack, search with the hexadecimal local thread ID, and you will find the corresponding thread at the nid of a certain line. Check the Java thread stack to find the corresponding Java class and line number, and then read the code to find the possible cause of the problem.
Instructions for tid/nid in jstack stack information
https://docs.oracle.com/javas...
The thread dump consists of the thread stack, including the thread state, for all Java threads in the virtual machine. The header line contains the following information about the thread: - Thread ID (tid), which is the address of a thread structure in memory. - ID of the native thread (nid).
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