Suppose we run program P in a computer system using the Linu

Suppose we run program P in a computer system using the Linux operating system. We use the Linux time command to collect some time measurements while P is running. The output from time is, real 53m27.589s user 24m41.850s system 1m3.337s What was the execution time of P? What was the user CPU time of P? What was the system CPU time of P? How much time during the execution of P did the system spend not executing the instructions of P nor OS in-striations on behalf of P? List and describe one factor or component of the time from exercise d, i.e., name one thing the system might have been doing during this time period.

Solution

Lets Start with Explaining what these measurements are:

Real: Actual clock time when you hit an action/button and till you get the expected output on your screen. This include all execution,wait,IO operations time added.

User: This is CPU time used in executing the process without any waiting outside the kernel.

System: This is CPU time used in executing the process without any waiting within the kernel.

Before any calculation lets convert the given data in seconds
Real = 53m27.589s = 3207.589s
User = 24m41.850s = 1481.850s
System = 1m3.337s = 63.337s

a) user+system is total execution time.
   execution time=1481.850+63.337=1545.187s=25m45.187m
b) This is CPU time used in executing the process without any waiting outside the kernel. User = 24m41.850s = 1481.850s
c)   This is CPU time used in executing the process without any waiting within the kernel. System = 1m3.337s = 63.337s
d) By definition the waiting/sleeping time=real-User-System
   3207.589-1481.850-63.337=1662.402s= 27m42.402sec
e) Executing other processes/programs in queue that can be user initiated programs or system originated(Operating System) programs but cannot be ideal.