The xv6-assignment from jashna24

TASK 1

Syscall waitx is implemented.
It is used to get total waittime and runtime of process.
Using Terminal we can access this syscall via 'time' command
time takes a command as an argument and prints the runtime and waitime of that command using waitx on the terminal.

						time <command>

Syscall detpinfo is implemented.
It is used to get information of a process like runtime,num_run, current_queue , ticks in different queues.
It will be used in case of multi level feedback queue scheduling.
Using Terminal we can access this syscall via 'info' command
info takes pid as an argument and prints the info of the process corresponding to the pid on the terminal.

						info <pid>

First in, first out (FIFO), also known as first come, first served (FCFS), is the simplest scheduling algorithm.
FIFO simply queues processes in the order that they arrive in the ready queue.
No preemption is allowed.
In this, the process that comes first will be executed first and next process starts only after the previous gets fully executed.
To change the default scheduling to FCFS , run the make in the following way:

				make clean qemu-nox SCHEDULER=FCFS

Priority scheduling is a preemptive algorithm.
Each process is assigned a priority. Process with highest priority (numerically least) is to be executed first and so on.
Processes with same priority are executed on first come first served basis.
If a process of higher priority(numerically less) arrives while a lower priority process is being executed the lower priority process is preempted.
To change the default scheduling to PBS , run the make in the following way:

				make clean qemu-nox SCHEDULER=PBS

Syscall set_priority is implemented.
It is used to change the priority of a process.
Using Terminal we can access this syscall via 'chngpr' command
chngpr takes pid of the process and the new priority as an argument and prints the old priority on the terminal.

				chngpr <pid> <new_priority>

Multilevel feedback queue scheduling, processes are initially assigned the 0th queue out of total 5 queues.
It allows a process to move between queues. If a process uses too much CPU time, it will be moved to a lower-priority queue. Similarly, a process that waits too long in a lower-priority queue may be moved to a higher-priority queue. This form of aging prevents starvation.
To change the default scheduling to MLFQ , run the make in the following way:

			make clean qemu-nox SCHEDULER=MLFQ