Ps

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ps - report a snapshot of the current processes.

How to read PS (Basics)


Example:

$ ps
 PID TTY          TIME CMD
8741 pts/0    00:00:00 bash
8863 pts/0    00:00:00 ps
  • PID = Process ID
  • pts = Psuedo Terminal Session

Show all processes running on the system:

$ ps -ef
UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0 May10 ?        00:00:25 /usr/lib/systemd/systemd --switched-root --system --deserialize 22
root         2     0  0 May10 ?        00:00:00 [kthreadd]
root         4     2  0 May10 ?        00:00:00 [kworker/0:0H]
root         5     2  0 May10 ?        00:00:01 [kworker/u4:0]
root         6     2  0 May10 ?        00:00:00 [mm_percpu_wq]
root         7     2  0 May10 ?        00:00:00 [ksoftirqd/0]
root         8     2  0 May10 ?        00:00:08 [rcu_sched]
root         9     2  0 May10 ?        00:00:00 [rcu_bh]
root        10     2  0 May10 ?        00:00:00 [migration/0]
root        11     2  0 May10 ?        00:00:00 [watchdog/0]
root        12     2  0 May10 ?        00:00:00 [cpuhp/0]
root        13     2  0 May10 ?        00:00:00 [cpuhp/1]
root        14     2  0 May10 ?        00:00:00 [watchdog/1]
root        15     2  0 May10 ?        00:00:00 [migration/1]
root        16     2  0 May10 ?        00:00:00 [ksoftirqd/1]
root        18     2  0 May10 ?        00:00:00 [kworker/1:0H] 
  • PPID = Parent PID
  • ? = Process running as a daemon, not attached to the terminal.
  • Commands in [] = Kernel threads


How to find the processor which a process is running on


1. Run the following commands and then review the output to determine the following:

  • The process ID of the process. In this example, we are showing the aws-replication-agent process.
# pidof <process>
# pidof /var/lib/aws-replication-agent/jre/bin/java
  • The CPU core (indicated by psr) that it's running on.
# ps --pid $(pidof <process>) -o psr,pid,comm
# ps --pid $(pidof /var/lib/aws-replication-agent/jre/bin/java) -o psr,pid,comm

Then, check the CPU utilization of the identified CPU core.

# mpstat -P <psr column value> 3