Shulou(Shulou.com)06/03 Report--

1. Jstack command

View thread stack information within a Java process.

Jstack can navigate to the thread stack, and we can navigate to specific code based on stack information, so it is used a lot in JVM performance tuning.

two。 Hot CPU issues:

The occupancy rate of cpu is relatively high.

Positioning steps:

Jps-m-l lists running processes-is it better to use the top command here? Top can see who occupies the highest cpu.

Top-H-p pid finds the thread in the process that consumes the most cpu

Printf "% x\ n" tid thread id converted to hexadecimal

Jstack pid | convert grep to hexadecimal tid-A 50

Note 1: in the information displayed, focus on the code written by yourself, and take screenshots for the developer.

Note 2: it is possible that jstack cannot capture the required information at one time, so it needs to be executed multiple times, because it captures the state of that moment.

3. Java.lang.stackoverflowerror,fatal:stack size too small

Parameter:-Xss: stack size of each thread, which is used to save function calls, return addresses, etc. The default value is 1m. If an error is reported, it will be changed to 2m.

Code: take a memory snapshot to troubleshoot the code, it is possible that there are too many levels of recursive calls

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