xv6

Makefile

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+OBJS = \
+	bio.o\
+	console.o\
+	exec.o\
+	file.o\
+	fs.o\
+	ide.o\
+	ioapic.o\
+	kalloc.o\
+	kbd.o\
+	lapic.o\
+	log.o\
+	main.o\
+	mp.o\
+	picirq.o\
+	pipe.o\
+	proc.o\
+	sleeplock.o\
+	spinlock.o\
+	string.o\
+	swtch.o\
+	syscall.o\
+	sysfile.o\
+	sysproc.o\
+	trapasm.o\
+	trap.o\
+	uart.o\
+	vectors.o\
+	vm.o\
+
+# Cross-compiling (e.g., on Mac OS X)
+# TOOLPREFIX = i386-jos-elf
+
+# Using native tools (e.g., on X86 Linux)
+#TOOLPREFIX =
+
+# Try to infer the correct TOOLPREFIX if not set
+ifndef TOOLPREFIX
+TOOLPREFIX := $(shell if i386-jos-elf-objdump -i 2>&1 | grep '^elf32-i386$$' >/dev/null 2>&1; \
+	then echo 'i386-jos-elf-'; \
+	elif objdump -i 2>&1 | grep 'elf32-i386' >/dev/null 2>&1; \
+	then echo ''; \
+	else echo "***" 1>&2; \
+	echo "*** Error: Couldn't find an i386-*-elf version of GCC/binutils." 1>&2; \
+	echo "*** Is the directory with i386-jos-elf-gcc in your PATH?" 1>&2; \
+	echo "*** If your i386-*-elf toolchain is installed with a command" 1>&2; \
+	echo "*** prefix other than 'i386-jos-elf-', set your TOOLPREFIX" 1>&2; \
+	echo "*** environment variable to that prefix and run 'make' again." 1>&2; \
+	echo "*** To turn off this error, run 'gmake TOOLPREFIX= ...'." 1>&2; \
+	echo "***" 1>&2; exit 1; fi)
+endif
+
+# If the makefile can't find QEMU, specify its path here
+QEMU = qemu-system-x86_64
+
+# Try to infer the correct QEMU
+ifndef QEMU
+QEMU = $(shell if which qemu > /dev/null; \
+	then echo qemu; exit; \
+	elif which qemu-system-i386 > /dev/null; \
+	then echo qemu-system-i386; exit; \
+	elif which qemu-system-x86_64 > /dev/null; \
+	then echo qemu-system-x86_64; exit; \
+	else \
+	qemu=/Applications/Q.app/Contents/MacOS/i386-softmmu.app/Contents/MacOS/i386-softmmu; \
+	if test -x $$qemu; then echo $$qemu; exit; fi; fi; \
+	echo "***" 1>&2; \
+	echo "*** Error: Couldn't find a working QEMU executable." 1>&2; \
+	echo "*** Is the directory containing the qemu binary in your PATH" 1>&2; \
+	echo "*** or have you tried setting the QEMU variable in Makefile?" 1>&2; \
+	echo "***" 1>&2; exit 1)
+endif
+
+CC = $(TOOLPREFIX)gcc
+AS = $(TOOLPREFIX)gas
+LD = $(TOOLPREFIX)ld
+OBJCOPY = $(TOOLPREFIX)objcopy
+OBJDUMP = $(TOOLPREFIX)objdump
+CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer
+#CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -fvar-tracking -fvar-tracking-assignments -O0 -g -Wall -MD -gdwarf-2 -m32 -Werror -fno-omit-frame-pointer
+CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
+ASFLAGS = -m32 -gdwarf-2 -Wa,-divide
+# FreeBSD ld wants ``elf_i386_fbsd''
+LDFLAGS += -m $(shell $(LD) -V | grep elf_i386 2>/dev/null | head -n 1)
+
+xv6.img: bootblock kernel fs.img
+	dd if=/dev/zero of=xv6.img count=10000
+	dd if=bootblock of=xv6.img conv=notrunc
+	dd if=kernel of=xv6.img seek=1 conv=notrunc
+
+xv6memfs.img: bootblock kernelmemfs
+	dd if=/dev/zero of=xv6memfs.img count=10000
+	dd if=bootblock of=xv6memfs.img conv=notrunc
+	dd if=kernelmemfs of=xv6memfs.img seek=1 conv=notrunc
+
+bootblock: bootasm.S bootmain.c
+	$(CC) $(CFLAGS) -fno-pic -O -nostdinc -I. -c bootmain.c
+	$(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c bootasm.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0x7C00 -o bootblock.o bootasm.o bootmain.o
+	$(OBJDUMP) -S bootblock.o > bootblock.asm
+	$(OBJCOPY) -S -O binary -j .text bootblock.o bootblock
+	./sign.pl bootblock
+
+entryother: entryother.S
+	$(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c entryother.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0x7000 -o bootblockother.o entryother.o
+	$(OBJCOPY) -S -O binary -j .text bootblockother.o entryother
+	$(OBJDUMP) -S bootblockother.o > entryother.asm
+
+initcode: initcode.S
+	$(CC) $(CFLAGS) -nostdinc -I. -c initcode.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0 -o initcode.out initcode.o
+	$(OBJCOPY) -S -O binary initcode.out initcode
+	$(OBJDUMP) -S initcode.o > initcode.asm
+
+kernel: $(OBJS) entry.o entryother initcode kernel.ld
+	$(LD) $(LDFLAGS) -T kernel.ld -o kernel entry.o $(OBJS) -b binary initcode entryother
+	$(OBJDUMP) -S kernel > kernel.asm
+	$(OBJDUMP) -t kernel | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernel.sym
+
+# kernelmemfs is a copy of kernel that maintains the
+# disk image in memory instead of writing to a disk.
+# This is not so useful for testing persistent storage or
+# exploring disk buffering implementations, but it is
+# great for testing the kernel on real hardware without
+# needing a scratch disk.
+MEMFSOBJS = $(filter-out ide.o,$(OBJS)) memide.o
+kernelmemfs: $(MEMFSOBJS) entry.o entryother initcode kernel.ld fs.img
+	$(LD) $(LDFLAGS) -T kernel.ld -o kernelmemfs entry.o  $(MEMFSOBJS) -b binary initcode entryother fs.img
+	$(OBJDUMP) -S kernelmemfs > kernelmemfs.asm
+	$(OBJDUMP) -t kernelmemfs | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernelmemfs.sym
+
+tags: $(OBJS) entryother.S _init
+	etags *.S *.c
+
+vectors.S: vectors.pl
+	perl vectors.pl > vectors.S
+
+ULIB = ulib.o usys.o printf.o umalloc.o
+
+_%: %.o $(ULIB)
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o $@ $^
+	$(OBJDUMP) -S $@ > $*.asm
+	$(OBJDUMP) -t $@ | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > $*.sym
+
+_forktest: forktest.o $(ULIB)
+	# forktest has less library code linked in - needs to be small
+	# in order to be able to max out the proc table.
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o _forktest forktest.o ulib.o usys.o
+	$(OBJDUMP) -S _forktest > forktest.asm
+
+mkfs: mkfs.c fs.h
+	gcc -Werror -Wall -o mkfs mkfs.c
+
+# Prevent deletion of intermediate files, e.g. cat.o, after first build, so
+# that disk image changes after first build are persistent until clean.  More
+# details:
+# http://www.gnu.org/software/make/manual/html_node/Chained-Rules.html
+.PRECIOUS: %.o
+
+UPROGS=\
+	_cat\
+	_echo\
+	_forktest\
+	_grep\
+	_init\
+	_kill\
+	_ln\
+	_ls\
+	_mkdir\
+	_rm\
+	_sh\
+	_stressfs\
+	_usertests\
+	_wc\
+	_ps\
+	_nice\
+	_foo\
+	_zombie\
+
+fs.img: mkfs README $(UPROGS)
+	./mkfs fs.img README $(UPROGS)
+
+-include *.d
+
+clean:
+	rm -f *.tex *.dvi *.idx *.aux *.log *.ind *.ilg \
+	*.o *.d *.asm *.sym vectors.S bootblock entryother \
+	initcode initcode.out kernel xv6.img fs.img kernelmemfs mkfs \
+	.gdbinit \
+	$(UPROGS)
+
+# make a printout
+FILES = $(shell grep -v '^\#' runoff.list)
+PRINT = runoff.list runoff.spec README toc.hdr toc.ftr $(FILES)
+
+xv6.pdf: $(PRINT)
+	./runoff
+	ls -l xv6.pdf
+
+print: xv6.pdf
+
+# run in emulators
+
+bochs : fs.img xv6.img
+	if [ ! -e .bochsrc ]; then ln -s dot-bochsrc .bochsrc; fi
+	bochs -q
+
+# try to generate a unique GDB port
+GDBPORT = $(shell expr `id -u` % 5000 + 25000)
+# QEMU's gdb stub command line changed in 0.11
+QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
+	then echo "-gdb tcp::$(GDBPORT)"; \
+	else echo "-s -p $(GDBPORT)"; fi)
+ifndef CPUS
+CPUS := 2
+endif
+QEMUOPTS = -drive file=fs.img,index=1,media=disk,format=raw -drive file=xv6.img,index=0,media=disk,format=raw -smp $(CPUS) -m 512 $(QEMUEXTRA)
+
+qemu: fs.img xv6.img
+	$(QEMU) -serial mon:stdio $(QEMUOPTS)
+
+qemu-memfs: xv6memfs.img
+	$(QEMU) -drive file=xv6memfs.img,index=0,media=disk,format=raw -smp $(CPUS) -m 256
+
+qemu-nox: fs.img xv6.img
+	$(QEMU) -nographic $(QEMUOPTS)
+
+.gdbinit: .gdbinit.tmpl
+	sed "s/localhost:1234/localhost:$(GDBPORT)/" < $^ > $@
+
+qemu-gdb: fs.img xv6.img .gdbinit
+	@echo "*** Now run 'gdb'." 1>&2
+	$(QEMU) -serial mon:stdio $(QEMUOPTS) -S $(QEMUGDB)
+
+qemu-nox-gdb: fs.img xv6.img .gdbinit
+	@echo "*** Now run 'gdb'." 1>&2
+	$(QEMU) -nographic $(QEMUOPTS) -S $(QEMUGDB)
+
+# CUT HERE
+# prepare dist for students
+# after running make dist, probably want to
+# rename it to rev0 or rev1 or so on and then
+# check in that version.
+
+EXTRA=\
+	mkfs.c ulib.c user.h cat.c echo.c forktest.c grep.c kill.c\
+	ln.c ls.c mkdir.c rm.c stressfs.c usertests.c wc.c ps.c nice.c foo.c zombie.c\
+	printf.c umalloc.c\
+	README dot-bochsrc *.pl toc.* runoff runoff1 runoff.list\
+	.gdbinit.tmpl gdbutil\
+
+dist:
+	rm -rf dist
+	mkdir dist
+	for i in $(FILES); \
+	do \
+		grep -v PAGEBREAK $$i >dist/$$i; \
+	done
+	sed '/CUT HERE/,$$d' Makefile >dist/Makefile
+	echo >dist/runoff.spec
+	cp $(EXTRA) dist
+
+dist-test:
+	rm -rf dist
+	make dist
+	rm -rf dist-test
+	mkdir dist-test
+	cp dist/* dist-test
+	cd dist-test; $(MAKE) print
+	cd dist-test; $(MAKE) bochs || true
+	cd dist-test; $(MAKE) qemu
+
+# update this rule (change rev#) when it is time to
+# make a new revision.
+tar:
+	rm -rf /tmp/xv6
+	mkdir -p /tmp/xv6
+	cp dist/* dist/.gdbinit.tmpl /tmp/xv6
+	(cd /tmp; tar cf - xv6) | gzip >xv6-rev10.tar.gz  # the next one will be 10 (9/17)
+
+.PHONY: dist-test dist

README.md

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+#### Roll Number - 20161035
+#### OS Assignment 5
+
+* Priority Based Scheduler - Priority scheduling involves priority assignment to every process, and processes with higher priorities are carried out first, whereas tasks with equal priorities are carried out on round robin basis.
+
+* Made 2 files **foo.c** (Its forking new processes for testing by doing useless calculations) and **nice.c**
+(Its used to set priority according to the mentioned pid).
+
+#### Comparison between Round Robin and Priority based scheduler on the basis of starvation
+
+* Round robin allocates time slices to each process in a cyclic manner and stops starvation.
+* Priority based scheduling may cause starvation because **high priority** (low number) processes will
+  given be given preference over **low priority** (high number) processes.
+* With same priority proesses, Round robin scheduler is used.
+
+#### Round Robin
+![Round Robin](RR.png)
+
+#### Priority Based
+![Priority Scheduler](PS.png)
+
+#### Useful Links:-
+![1](https://www.youtube.com/watch?v=hIXRrv-cBA4&feature=youtu.be)
+![2](https://www.youtube.com/watch?v=DZ0-GMtOtEc&feature=youtu.be)
+![3](https://www.youtube.com/watch?v=21SVYiKhcwM)