I would like to monitor the number of threads used by a specific process on Linux. Is there an easy way to get this information without impacting the performance of the process?
18 Answers
My answer is more gui, but still within terminal. Htop may be used with a bit of setup.
- Start htop.
- Enter setup menu by pressing F2.
- From leftmost column choose "Columns"
- From rightmost column choose the column to be added to main monitoring output, "NLWP" is what you are looking for.
- Press F10.
JStack is quite inexpensive - one option would be to pipe the output through grep to find active threads and then pipe through wc -l.
More graphically is JConsole, which displays the thread count for a given process.
Newer JDK distributions ship with JConsole and VisualVM. Both are fantastic tools for getting the dirty details from a running Java process. If you have to do this programmatically, investigate JMX.
The easiest way is using "htop". You can install "htop" (a fancier version of top) which will show you all your cores, process and memory usage.
Press "Shift+H" to show all process or press again to hide it. Press "F4" key to search your process name.
Installing on Ubuntu or Debian:
sudo apt-get install htop
Installing on Redhat or CentOS:
yum install htop
dnf install htop [On Fedora 22+ releases]
If you want to compile "htop" from source code, you will find it here.
If you're looking for thread count for multiple processes, the other answers won't work well for you, since you won't see the process names or PIDs, which makes them rather useless. Use this instead:
ps -o pid,nlwp,args -p <pid_1> <pid_2> ... <pid_N>
In order to watch the changes live, just add watch:
watch ps -o pid,nlwp,args -p <pid_1> <pid_2> ... <pid_N>
If you want the number of threads per user in a linux system then you should use:
ps -eLf | grep <USER> | awk '{ num += $6 } END { print num }'
where as <USER> use the desired user name.
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