A better xv6

Introduction

This is a modification of the xv6 operating system in which the following features have been implemented:

• waitx system call
• getpinfo system call
• First-come-first-serve CPU scheduler
• Priority-based CPU scheduler
• Multi-level-feedback-queue CPU scheduler

Details about the scope and implementation of these features are available in REPORT.pdf (or REPORT.md).

Get it running

1. Ensure you have the Qemu Emulator installed. If not:

# apt-get install qemu

2. Build the OS:

$ make [options]

3. Run on Qemu:

$ make qemu [options]

To clean up binaries and other intermediate files:

$ make clean

The options can be one or more of the following:

• CPUS=[1, 2, ...] Defaults to 1. The added features have been tested on up to 2 CPU cores.
• DEBUG=[TRUE, FALSE] Defaults to FALSE. Enabling DEBUG mode causes the OS to print scheduling information to STDOUT. The output is verbose and makes it hard to otherwise use the system.
• SCHEDULER=[FCFS, RR, PBS, MLFQ] Defaults to RR. The options stand for first-come-first-serve, round-robin, priority-based and multi-level-feedback-queue respectively.

Ensure that the options selected in step 2 and 3 are the same.

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ORIGINAL README:

xv6 is a re-implementation of Dennis Ritchie's and Ken Thompson's Unix Version 6 (v6). xv6 loosely follows the structure and style of v6, but is implemented for a modern x86-based multiprocessor using ANSI C.

ACKNOWLEDGMENTS

xv6 is inspired by John Lions's Commentary on UNIX 6th Edition (Peer to Peer Communications; ISBN: 1-57398-013-7; 1st edition (June 14, 2000)). See also https://pdos.csail.mit.edu/6.828/, which provides pointers to on-line resources for v6.

xv6 borrows code from the following sources: JOS (asm.h, elf.h, mmu.h, bootasm.S, ide.c, console.c, and others) Plan 9 (entryother.S, mp.h, mp.c, lapic.c) FreeBSD (ioapic.c) NetBSD (console.c)

The following people have made contributions: Russ Cox (context switching, locking), Cliff Frey (MP), Xiao Yu (MP), Nickolai Zeldovich, and Austin Clements.

We are also grateful for the bug reports and patches contributed by Silas Boyd-Wickizer, Anton Burtsev, Cody Cutler, Mike CAT, Tej Chajed, eyalz800, Nelson Elhage, Saar Ettinger, Alice Ferrazzi, Nathaniel Filardo, Peter Froehlich, Yakir Goaron,Shivam Handa, Bryan Henry, Jim Huang, Alexander Kapshuk, Anders Kaseorg, kehao95, Wolfgang Keller, Eddie Kohler, Austin Liew, Imbar Marinescu, Yandong Mao, Matan Shabtay, Hitoshi Mitake, Carmi Merimovich, Mark Morrissey, mtasm, Joel Nider, Greg Price, Ayan Shafqat, Eldar Sehayek, Yongming Shen, Cam Tenny, tyfkda, Rafael Ubal, Warren Toomey, Stephen Tu, Pablo Ventura, Xi Wang, Keiichi Watanabe, Nicolas Wolovick, wxdao, Grant Wu, Jindong Zhang, Icenowy Zheng, and Zou Chang Wei.

The code in the files that constitute xv6 is Copyright 2006-2018 Frans Kaashoek, Robert Morris, and Russ Cox.

ERROR REPORTS

We switched our focus to xv6 on RISC-V; see the mit-pdos/xv6-riscv.git repository on github.com.

BUILDING AND RUNNING XV6

To build xv6 on an x86 ELF machine (like Linux or FreeBSD), run "make". On non-x86 or non-ELF machines (like OS X, even on x86), you will need to install a cross-compiler gcc suite capable of producing x86 ELF binaries (see https://pdos.csail.mit.edu/6.828/). Then run "make TOOLPREFIX=i386-jos-elf-". Now install the QEMU PC simulator and run "make qemu".