Question

I want to know the CPU utilization of a process and all the child processes, for a fixed period of time, in Linux.

To be more specific, here is my use-case:

There is a process which waits for a request from the user to execute the programs. To execute the programs, this process invokes child processes (maximum limit of 5 at a time) & each of this child process executes 1 of these submitted programs (let’s say user submitted 15 programs at once). So, if user submits 15 programs, then 3 batches of 5 child processes each will run. Child processes are killed as soon as they finish their execution of the program.

I want to know about % CPU Utilization for the parent process and all its child process during the execution of those 15 programs.

Is there any simple way to do this using top or another command? (Or any tool i should attach to the parent process.)

Answer 1

You can find this information in /proc/PID/stat where PID is your parent process’s process ID. Assuming that the parent process waits for its children then the total CPU usage can be calculated from utime, stime, cutime and cstime:

utime %lu

Amount of time that this process has been scheduled in user mode,
measured in clock ticks (divide by sysconf(_SC_CLK_TCK). This includes
guest time, guest_time (time spent running a virtual CPU, see below),
so that applications that are not aware of the guest time field do not
lose that time from their calculations.

stime %lu

Amount of time that this process has been scheduled in kernel mode,
measured in clock ticks (divide by sysconf(_SC_CLK_TCK).

cutime %ld

Amount of time that this process’s waited-for children have been
scheduled in user mode, measured in clock ticks (divide by
sysconf(_SC_CLK_TCK). (See also times(2).) This includes guest time,
cguest_time (time spent running a virtual CPU, see below).

cstime %ld

Amount of time that this process’s waited-for children have been
scheduled in kernel mode, measured in clock ticks (divide by
sysconf(_SC_CLK_TCK).

See proc(5) manpage for details.