How can I monitor the thread count of a process on linux?

Question

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?

Answer 1

try

ps huH p <PID_OF_U_PROCESS> | wc -l

or htop

Answer 2

To get the number of threads for a given pid:

$ ps -o nlwp <pid>

Where nlwp stands for Number of Light Weight Processes (threads). Thus ps aliases nlwp to thcount, which means that

$ ps -o thcount <pid>

does also work.

If you want to monitor the thread count, simply use watch:

$ watch ps -o thcount <pid>

To get the sum of all threads running in the system:

$ ps -eo nlwp | tail -n +2 | awk '{ num_threads += $1 } END { print num_threads }'

Answer 3

Each thread in a process creates a directory under /proc/<pid>/task. Count the number of directories, and you have the number of threads.

Answer 4

cat /proc/<PROCESS_PID>/status | grep Threads

Answer 5

ps -eLf on the shell shall give you a list of all the threads and processes currently running on the system. Or, you can run top command then hit 'H' to toggle thread listings.

Answer 6

If you use:

ps uH p <PID_OF_U_PROCESS> | wc -l

You have to subtract 1 to the result, as one of the lines "wc" is counting is the headers of the "ps" command.

Answer 7

$ ps H p pid-id

H - Lists all the individual threads in a process

or

$cat /proc/pid-id/status

pid-id is the Process ID

eg.. (Truncated the below output)

root@abc:~# cat /proc/8443/status
Name:   abcdd
State:  S (sleeping)
Tgid:   8443
VmSwap:        0 kB
Threads:    4
SigQ:   0/256556
SigPnd: 0000000000000000

Answer 8

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.

Answer 9

Here is one command that displays the number of threads of a given process :

ps -L -o pid= -p <pid> | wc -l

Unlike the other ps based answers, there is here no need to substract 1 from its output as there is no ps header line thanks to the -o pid=option.

Answer 10

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.

Answer 11

My answer is more gui, but still within terminal. Htop may be used with a bit of setup.

1. Start htop.
2. Enter setup menu by pressing F2.
3. From leftmost column choose "Columns"
4. From rightmost column choose the column to be added to main monitoring output, "NLWP" is what you are looking for.
5. Press F10.

Answer 12

jvmtop can show the current jvm thread count beside other metrics.

Answer 13

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.

Answer 14

If you are trying to find out the number of threads using cpu for a given pid I would use:

top -bc -H -n2 -p <pid> | awk '{if ($9 != "0.0" && $1 ~ /^[0-9]+$/) print $1 }' | sort -u | wc -l

Answer 15

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.

Answer 16

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>

Answer 17

If you're interested in those threads which are really active -- as in doing something (not blocked, not timed_waiting, not reporting "thread running" but really waiting for a stream to give data) as opposed to sitting around idle but live -- then you might be interested in jstack-active.

This simple bash script runs jstack then filters out all the threads which by heuristics seem to be idling, showing you stack traces for those threads which are actually consuming CPU cycles.

Answer 18

VisualVM can show clear states of threads of a given JVM process