How to count number of executed instructions of a process id including child processes

Question

I have nodejs application (as a server) deployed as a Docker container and I want to count the number of executed instructions when I call a function in it.

Here is how I find the container's PID:

$ pstree -p | grep node | grep npm
           |                 |-containerd-shim(114397)-+-npm(114414)-+-sh(114540)---node(114541)-+-{node}(114542)

Then, I need to know the Docker ID:

$ docker ps | grep workload
root@node3:/home/m# docker ps | grep workload | grep npm
c7457f74536b        michelgokan/synthetic-workload-generator                   "npm start"              55 minutes ago      Up 55 minutes                           k8s_whatever_workload-5697bb48f9-gg8j5_default_896e5938-55f2-4875-bf6c-2bff2acbe0c6_0

Now, I know the parent PID is 114397. So I run the following perf command:

$ perf stat -p 114397 -e instructions,cycles,task-clock docker exec -it c7457f74536b curl 127.0.0.1:30005/workload/cpu
1000 CHKSM AND DIFFIEHELLMAN 60 OK!
 Performance counter stats for process id '114397':

         170057460      instructions              #    1.02  insn per cycle         
         166389574      cycles                    #    1.575 GHz                    
            105.67 msec task-clock                #    0.570 CPUs utilized          

       0.185362408 seconds time elapsed

It seems it's not including instructions executed by the child processes. So I tried the following:

$ perf stat -p 1,722,114397,114414,114540,114541,114542 -e instructions,cycles,task-clock docker exec -it c7457f74536b curl 127.0.0.1:30005/workload/cpu
1000 CHKSM AND DIFFIEHELLMAN 60 OK!
 Performance counter stats for process id '1,722,114397,114414,114540,114541,114542':

         249803992      instructions              #    1.05  insn per cycle         
         236979702      cycles                    #    1.575 GHz                    
            150.47 msec task-clock                #    0.832 CPUs utilized          

       0.180848729 seconds time elapsed

In which 1 is the systemd and 722 is the parent containerd PID of containers.

Questions:

1. Is there any way that I can provide the parent PID and it counts number of executed instructions of all processes?
2. Does my approach make sense? I mean the way I provided all the PIDs in a comma-separated format.

Answer 1

You can get the PID of one of you processes (the parent) and deduce the others using pgrep.

pgrep has a neat feature --ns which will get you all the processes running in the same PID namespace as a given PID.

Having that you can get all the child process and convert them to comma separated values and feed them to perf

$ perf stat -p $(pgrep --ns <pid> | paste -s -d ",") -e instructions,cycles,task-clock docker exec -it c7457f74536b curl 127.0.0.1:30005/workload/cpu

pgrep --ns will get you the pid and paste -s -d "," will convert them.