xv6 - OSTEP

This repository contains my implementation for OSTEP xv6 Kernel Projcts based on the xv6 Kernel by MIT.

Modifications

1. Added new system call getreadcount() which returns the total number of disk read operations done since system boot
   • Tested using readtest.c, which adds the readtest command to verify disk read counting.
2. changed the Scheduling Policy from round robin to lottery scheduling

   • Each process has a number of tickets determining its likelihood of being scheduled.

   • The scheduler conducts a lottery after every time slice to select the process to run, ensuring proportional CPU allocation based on ticket count.

   • Processes inherit their parent's ticket count by default, with the INIT_TICKETS value assigned to the initial process.

   • Processes can update their ticket count using the settickets() system call (up to a maximum of MAX_TICKETS).

   • Added the getpinfo() system call used to retrieve processes information

     • is the process in use or not.
     • Ticket count.
     • Process ID.
     • Number of lotteries won.

   • test_lottery [time-to-run] [tickets-num] command is provided to test the scheduler

     test_lottery 100 1 &; test_lottery 100 100
     
     process with 100 tickets is running
     process with 100 tickets is running
     process with 100 tickets is running
     ...
     process with 1 tickets is running

3. Added v2paddr(void *va) system call used to get the physical address that a given virtual address maps to

   • test_v2p [virtual-addresses-range-start] [virtual-addresses-range-end] command is provided to test it

     $ test_v2p 10000 10010
     Physical Address Of 10001: 234309393
     Physical Address Of 10000: 234309392
     ...
     Physical Address Of 10009: 234309401
     
     $ test_v2p 100000 100010
     Invalid Virtual Address
     Invalid Virtual Address
     ...

Usage

• Prerequisites: make qemu gcc
• Build

  make qemu