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Recently I have noticed that one of our applications crossed the allowed threshold for creating new threads in a test server. After a talk with Ops guy, we gotta to know that it had around 5k+ (O_O) threads running already for no reason. Probably a memory leak that we can have it for another day.

For now, let me share you the way to find the process and its threads in linux.

Know the process id.

First of all, we need the process id in order to list out the threads being created by said process.

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$ top -H -u ashokma

PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+  	COMMAND
3173 ashokma   20   0 2720980 429424  99644 S   5.6   2.7   4:49.63 	Compositor
3166 ashokma   20   0 2720980 429424  99644 S   4.6   2.7   1:53.81 	teams

Let’s take the process teams for instance. It’s id is 3166.

List the number of threads

Using the following command we can list out the number of threads.

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$ ps -T -p 3166
    PID    SPID TTY          TIME CMD
   3166    3166 ?        00:02:02 teams
   3166    3168 ?        00:00:00 ThreadPoolServi
   3166    3170 ?        00:01:47 Chrome_ChildIOT
   3166    3171 ?        00:00:00 GpuMemoryThread
   3166    3173 ?        00:05:17 Compositor
   3166    3174 ?        00:00:00 ThreadPoolSingl
   3166    3175 ?        00:00:01 CompositorTileW
   3166    3176 ?        00:00:01 CompositorTileW
   3166    3177 ?        00:00:01 CompositorTileW
   3166    3178 ?        00:00:01 CompositorTileW
   3166    3179 ?        00:00:00 CompositorTileW
   3166    3180 ?        00:00:00 teams
   3166    3184 ?        00:00:00 Watchdog
   3166    3199 ?        00:00:01 SharedWorker th
   3166    3205 ?        00:00:00 DedicatedWorker
   3166    3328 ?        00:00:00 Media
   3166   71782 ?        00:00:00 ThreadPoolForeg
   3166   71915 ?        00:00:00 ThreadPoolForeg
   3166   71916 ?        00:00:00 ThreadPoolForeg
   3166   71917 ?        00:00:00 ThreadPoolForeg
   3166   71918 ?        00:00:00 ThreadPoolForeg
   3166   71919 ?        00:00:00 ThreadPoolForeg
   3166   71920 ?        00:00:00 ThreadPoolForeg

Pro Tip: To quickly know the number of threads just chain the above command with wordcount (wc) as follows:

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$ ps -T -p 3166 | wc -l
21
# This varies realtime as the threads are being closed and created over the time.
#Linux #Pop!_OS #Terminal