For implementing this, make the required changes in scheduler function in proc.c file.

$//$Replace the scheduler function with the one below for priority round robin scheduling$//$ Loop over process table looking for process to run.acquire$($&ptable.lock$)$;for$($p $=$ ptable.proc; p $$ &ptable.proc$[$NPROC$]$; p$++)\{$ if$($p$->$state $!=$ RUNNABLE$)$ continue; $//$ Switch to chosen process. It is the process's job $//$ to release ptable.lock and then reacquire it $//$ before jumping back to us$.$ highP $=$ p; $//$choose one with highest priority for$($p$1=$ ptable.proc; p$1$ &ptable.proc$[$NPROC$]$; p$1++)\{$ if$($p$1->$state $!=$ RUNNABLE$)$ continue; if$($highP$->$priority $>$ pl$->$priority$)//$larger value, lower

priority

highP $=$ p$1$;

$\}$

p $=$ highP;

c$->$proc $=$ p;

switchuvm$($p$)$;

p$->$state $=$ RUNNING;

swtch$($&$($c$->$scheduler$),$ p$->$context$)$;

switchkvm$()$;

$//$ Process is done running for now.

$//$ It should have changed its p$->$state before coming back.

c$->$proc $=0$;

$\}$

release$($&ptable.lock$)$;

$\}$

$\}$

At this step, you have implemented the system calls and changed the scheduling policy in xv$6.$ Now, let us try it out.