add swap

Author: yangminz

src/hardware/cpu/mmu.c

@@ -20,6 +20,9 @@
 static uint64_t page_walk(uint64_t vaddr_value);
 static void page_fault_handler(pte4_t *pte, address_t vaddr);
 
+int swap_in(uint64_t daddr, uint64_t ppn);
+int swap_out(uint64_t daddr, uint64_t ppn);
+
 // consider this function va2pa as functional
 uint64_t va2pa(uint64_t vaddr)
 {
@@ -151,9 +154,12 @@ static uint64_t page_walk(uint64_t vaddr_value)
 static void page_fault_handler(pte4_t *pte, address_t vaddr)
 {
     // select one victim physical page to swap to disk
+    assert(pte->present == 0);
 
     // this is the selected ppn for vaddr
     int ppn = -1;
+    pte4_t *victim = NULL;
+    uint64_t daddr = 0xffffffffffffffff;
 
     // 1. try to request one free physical page from DRAM
     // kernel's responsibility
@@ -181,7 +187,86 @@ static void page_fault_handler(pte4_t *pte, address_t vaddr)
 
     // 2. no free physical page: select one clean page (LRU) and overwrite
     // in this case, there is no DRAM - DISK transaction
+    int lru_ppn = -1;
+    int lru_time = -1;
+    for (int i = 0; i < MAX_NUM_PHYSICAL_PAGE; ++ i)
+    {
+        if (page_map[i].dirty == 0 && 
+            lru_time < page_map[i].time)
+        {
+            lru_time = page_map[i].time;
+            lru_ppn = i;
+        }
+    }
+    
+    if (-1 != lru_ppn && lru_ppn < MAX_NUM_PHYSICAL_PAGE)
+    {
+        ppn = lru_ppn;
+
+        // reversed mapping
+        victim = page_map[ppn].pte4;
+
+        victim->pte_value = 0;
+        victim->present = 0;
+        victim->daddr = page_map[ppn].daddr;
+
+        // load page from disk to physical memory first
+        daddr = pte->daddr;
+        swap_in(pte->daddr, ppn);
+
+        pte->pte_value = 0;
+        pte->present = 1;
+        pte->ppn = ppn;
+        pte->dirty = 0;
+
+        page_map[ppn].allocated = 1;
+        page_map[ppn].time = 0;
+        page_map[ppn].dirty = 0;
+        page_map[ppn].pte4 = pte;
+        page_map[ppn].daddr = daddr;
+
+        return;
+    }
 
     // 3. no free nor clean physical page: select one LRU victim
     // write back (swap out) the DIRTY victim to disk
+    lru_ppn = -1;
+    lru_time = -1;
+    for (int i = 0; i < MAX_NUM_PHYSICAL_PAGE; ++ i)
+    {
+        if (lru_time < page_map[i].time)
+        {
+            lru_time = page_map[i].time;
+            lru_ppn = i;
+        }
+    }
+
+    assert(0 <= lru_ppn && lru_ppn < MAX_NUM_PHYSICAL_PAGE);
+
+    ppn = lru_ppn;
+
+    // reversed mapping
+    victim = page_map[ppn].pte4;
+
+    // write back
+    swap_out(page_map[ppn].daddr, ppn);
+
+    victim->pte_value = 0;
+    victim->present = 0;
+    victim->daddr = page_map[ppn].daddr;
+
+    // load page from disk to physical memory first
+    daddr = pte->daddr;
+    swap_in(daddr, ppn);
+
+    pte->pte_value = 0;
+    pte->present = 1;
+    pte->ppn = ppn;
+    pte->dirty = 0;
+
+    page_map[ppn].allocated = 1;
+    page_map[ppn].time = 0;
+    page_map[ppn].dirty = 0;
+    page_map[ppn].pte4 = pte;
+    page_map[ppn].daddr = daddr;
 }

src/hardware/memory/swap.c

@@ -0,0 +1,60 @@
+/* BCST - Introduction to Computer Systems
+ * Author:      yangminz@outlook.com
+ * Github:      https://github.com/yangminz/bcst_csapp
+ * Bilibili:    https://space.bilibili.com/4564101
+ * Zhihu:       https://www.zhihu.com/people/zhao-yang-min
+ * This project (code repository and videos) is exclusively owned by yangminz 
+ * and shall not be used for commercial and profitting purpose 
+ * without yangminz's permission.
+ */
+
+// Dynamic Random Access Memory
+#include <string.h>
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "headers/cpu.h"
+#include "headers/memory.h"
+#include "headers/common.h"
+#include "headers/address.h"
+
+// each swap file is swap page
+// each line of this swap page is one uint64
+#define SWAP_PAGE_FILE_LINES 512
+
+// disk address counter
+static uint64_t internal_swap_daddr = 0;
+
+int swap_in(uint64_t daddr, uint64_t ppn)
+{
+    FILE *fr = NULL;
+    char filename[128];
+    sprintf(filename, "../files/swap/page-%ld.txt", daddr);
+    fr = fopen(filename, "r");
+    assert(fr != NULL);
+
+    uint64_t ppn_ppo = ppn << PHYSICAL_PAGE_OFFSET_LENGTH;
+    char buf[64] = {'0'};
+    for (int i = 0; i < SWAP_PAGE_FILE_LINES; ++ i)
+    {
+        char *str = fgets(buf, 64, fr);
+        *((uint64_t *)(&pm[ppn_ppo + i * 8])) = string2uint(str);
+    }
+    fclose(fr);
+}
+
+int swap_out(uint64_t daddr, uint64_t ppn)
+{
+    FILE *fw = NULL;
+    char filename[128];
+    sprintf(filename, "../files/swap/page-%ld.txt", daddr);
+    fw = fopen(filename, "w");
+    assert(fw != NULL);
+
+    uint64_t ppn_ppo = ppn << PHYSICAL_PAGE_OFFSET_LENGTH;
+    for (int i = 0; i < SWAP_PAGE_FILE_LINES; ++ i)
+    {
+        fprintf(fw, "0x%16lx\n", *((uint64_t *)(&pm[ppn_ppo + i * 8])));
+    }
+    fclose(fw);
+}

src/headers/memory.h

@@ -67,7 +67,7 @@ typedef union
     struct
     {
         uint64_t _present           : 1;
-        uint64_t swap_id            : 63;   // disk address
+        uint64_t daddr            : 63;   // disk address
     };
 } pte123_t; // PGD, PUD, PMD
 
@@ -96,7 +96,7 @@ typedef union
     struct
     {
         uint64_t _present           : 1;    // present = 0
-        uint64_t swap_id            : 63;   // disk address
+        uint64_t daddr            : 63;   // disk address
     };
 } pte4_t;   // PT
 
@@ -107,7 +107,11 @@ typedef struct
     int dirty;
     int time;   // LRU cache
 
+    // real world: mapping to anon_vma or address_space
+    // we simply the situation here
+    // TODO: if multiple processes are using this page? E.g. Shared library
     pte4_t *pte4;       // the reversed mapping: from PPN to page table entry
+    uint64_t daddr;   // binding the revesed mapping with mapping to disk
 } pd_t;
 
 // for each pagable (swappable) physical page