Extended the xv6 OS to include a Virtual Memory Manager with swapfile support and LRU cache. Supervised by Ed Jorgensen and Dr. Ajoy Datta in 2018 during my senior year at UNLV (RIP Dr. Datta :( ) Changes made: console.c --------- printaddr() method added changed %p to print address instead of integer defs.h ------- Added struct vminfo_struct; All new functions from kalloc.c procsmemorystats() and find_proc_pte() from proc.c vminfo and pgtabinfo internal functions from vm.c swapfile functions from swap.c & usermode swapfile initialization in swapuser.c exec.c ------ Removes LRU mappings from process before exec() overwrites page table Debug output & new statistics for processes initialized file.h & fs.c & fs.h ------ Support for double inode indirection added (for larger swapfile) init.c ------- init now spawns a temporary process to inititalize the swapfile before executing the shell kalloc.c --------- added statistical fields to kmem kswapmem data structure Added invoke_swapper(), kmaxprocsize(), kexistfreepages(), kfreepagecnt(), kallocatedpages(), kallocbeginning(), kgetfreelistptr() freerange() debug info printing kalloc() now invokes swapper to give a page, if none available main.c ------- Added kswapinit() step to initialize the swap space, just before userinit() Makefile -------- Now links swap.o Now links swapuser.o (ULIB args) Added 8MB SWAPFILE to fs.img UPROGS now includes zeb_test EXTRA now includes zeb_test.c, swap.c and swapuser.o memlayout.h ------------ PHYSTOP changed to various values (commented out) for testing swapping mkfs.c ------- Debugging info added to main(), currently commented out (for doubly-indirect inodes) balloc()/iappend() modified to allow doubly-indirect inodes param.h ------- FSSIZE increased from 1000 to 20985 for larger file system printf.h ------- printaddr() function added %p and %x now print addresses, not integers proc.h ------- Statistical fields related to swapping and page faults added swap.h, swap.c, swapuser.c (No modifications, files did not previously exist.) ------ Contains kernel & user swap/LRU API header & implementation syscall.c & syscall.h & sysfile.c --------- 4 system calls added: vminfo, pgtabinfo, setswapfilefd, sbrk_force_swapout sysproc.c --------- sys_sbrk() modified for lazy allocation sys_sbrk_force_swapout(), sys_vminfo(), and sys_pgtabinfo() added trap.c --------- Support for NULL reference protection, lazy allocation, swapping, and LRU added types.h --------- Added NULL constant and vminfo_struct data structure user.h ------- Added vminfo(), pgtabinfo(), setswapfilefd(), sbrk_force_swapout(), and swapinit() usermode API calls usys.S ------- Added vminfo, pgtabinfo, setswapfilefd, and sbrk_force_swapout system calls vm.c ----- Added support to copyuvm for lazy allocation, swapping, and LRU Added vminfo_internal() & pgtabinfo_internal() methods zeb_test.c ----------- Various tests of functionality added for virtual memory