#include <defs.h> #include <x86.h> #include <stdio.h> #include <string.h> #include <swap.h> #include <swap_fifo.h> #include <list.h> /* [wikipedia]The simplest Page Replacement Algorithm(PRA) is a FIFO algorithm. The first-in, first-out * page replacement algorithm is a low-overhead algorithm that requires little book-keeping on * the part of the operating system. The idea is obvious from the name - the operating system * keeps track of all the pages in memory in a queue, with the most recent arrival at the back, * and the earliest arrival in front. When a page needs to be replaced, the page at the front * of the queue (the oldest page) is selected. While FIFO is cheap and intuitive, it performs * poorly in practical application. Thus, it is rarely used in its unmodified form. This * algorithm experiences Belady's anomaly. * * Details of FIFO PRA * (1) Prepare: In order to implement FIFO PRA, we should manage all swappable pages, so we can * link these pages into pra_list_head according the time order. At first you should * be familiar to the struct list in list.h. struct list is a simple doubly linked list * implementation. You should know howto USE: list_init, list_add(list_add_after), * list_add_before, list_del, list_next, list_prev. Another tricky method is to transform * a general list struct to a special struct (such as struct page). You can find some MACRO: * le2page (in memlayout.h), (in future labs: le2vma (in vmm.h), le2proc (in proc.h),etc. */ list_entry_t pra_list_head; /* * (2) _fifo_init_mm: init pra_list_head and let mm->sm_priv point to the addr of pra_list_head. * Now, From the memory control struct mm_struct, we can access FIFO PRA */ static int _fifo_init_mm(struct mm_struct *mm) { list_init(&pra_list_head); mm->sm_priv = &pra_list_head; //cprintf(" mm->sm_priv %x in fifo_init_mm\n",mm->sm_priv); return 0; } /* * (3)_fifo_map_swappable: According FIFO PRA, we should link the most recent arrival page at the back of pra_list_head qeueue */ static int _fifo_map_swappable(struct mm_struct *mm, uintptr_t addr, struct Page *page, int swap_in) { list_entry_t *head=(list_entry_t*) mm->sm_priv; list_entry_t *entry=&(page->pra_page_link); assert(entry != NULL && head != NULL); //record the page access situlation /*LAB3 EXERCISE 2: YOUR CODE*/ //(1)link the most recent arrival page at the back of the pra_list_head qeueue. return 0; } /* * (4)_fifo_swap_out_victim: According FIFO PRA, we should unlink the earliest arrival page in front of pra_list_head qeueue, * then set the addr of addr of this page to ptr_page. */ static int _fifo_swap_out_victim(struct mm_struct *mm, struct Page ** ptr_page, int in_tick) { list_entry_t *head=(list_entry_t*) mm->sm_priv; assert(head != NULL); assert(in_tick==0); /* Select the victim */ /*LAB3 EXERCISE 2: YOUR CODE*/ //(1) unlink the earliest arrival page in front of pra_list_head qeueue //(2) set the addr of addr of this page to ptr_page return 0; } static int _fifo_check_swap(void) { cprintf("write Virt Page c in fifo_check_swap\n"); *(unsigned char *)0x3000 = 0x0c; assert(pgfault_num==4); cprintf("write Virt Page a in fifo_check_swap\n"); *(unsigned char *)0x1000 = 0x0a; assert(pgfault_num==4); cprintf("write Virt Page d in fifo_check_swap\n"); *(unsigned char *)0x4000 = 0x0d; assert(pgfault_num==4); cprintf("write Virt Page b in fifo_check_swap\n"); *(unsigned char *)0x2000 = 0x0b; assert(pgfault_num==4); cprintf("write Virt Page e in fifo_check_swap\n"); *(unsigned char *)0x5000 = 0x0e; assert(pgfault_num==5); cprintf("write Virt Page b in fifo_check_swap\n"); *(unsigned char *)0x2000 = 0x0b; assert(pgfault_num==5); cprintf("write Virt Page a in fifo_check_swap\n"); *(unsigned char *)0x1000 = 0x0a; assert(pgfault_num==6); cprintf("write Virt Page b in fifo_check_swap\n"); *(unsigned char *)0x2000 = 0x0b; assert(pgfault_num==7); cprintf("write Virt Page c in fifo_check_swap\n"); *(unsigned char *)0x3000 = 0x0c; assert(pgfault_num==8); cprintf("write Virt Page d in fifo_check_swap\n"); *(unsigned char *)0x4000 = 0x0d; assert(pgfault_num==9); return 0; } static int _fifo_init(void) { return 0; } static int _fifo_set_unswappable(struct mm_struct *mm, uintptr_t addr) { return 0; } static int _fifo_tick_event(struct mm_struct *mm) { return 0; } struct swap_manager swap_manager_fifo = { .name = "fifo swap manager", .init = &_fifo_init, .init_mm = &_fifo_init_mm, .tick_event = &_fifo_tick_event, .map_swappable = &_fifo_map_swappable, .set_unswappable = &_fifo_set_unswappable, .swap_out_victim = &_fifo_swap_out_victim, .check_swap = &_fifo_check_swap, };