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