static unsigned take_phys_page()
{
unsigned page; /* Page to be replaced. */
page = (*replace)(); //calls either fifo_page_replace or second_chance_replace, can be found in main
coremap_entry_t* e = &coremap[page]; //fetch physical page address
if (e->owner==NULL) //no owner, free space - just use it!
return page;
page_table_entry_t* pt = e->owner;
// printf("has owner!\r\n");
if (pt->ondisk) {
//is located on disk, check if modified
// printf("on disk!\r\n");
if (pt->modified)
write_page(page,e->page);
pt->page = e->page;
} else {
// printf("not on disk!\r\n");
unsigned sw = new_swap_page();
pt->page = sw;
write_page(page,sw);
}
pt->ondisk = 1;
pt->modified = 0;
pt->inmemory = 0;
pt->referenced = 0;
return page;
}
static unsigned take_phys_page(unsigned virt_page)
{
unsigned page; /* Page to be replaced. */
coremap_entry_t *coremap_entry;
page_table_entry_t *swap_entry;
page = (*replace)();
/*printf("\t%x\n", page);*/
// I renamed ram_entry to coremap_entry:
coremap_entry = &coremap[page]; // "page" is the page in RAM we want to replace,
// and coremap_entry->page is the same page but on swap.
swap_entry = &page_table[virt_page]; // swap_entry->page is the page we want to get,
// now (probably) on swap. We want to write this page to "page".
if (coremap_entry->owner != NULL) {
if (coremap_entry->owner->modified) {
if (!coremap_entry->owner->ondisk) {
coremap_entry->page = new_swap_page();
coremap_entry->owner->ondisk = 1;
}
write_page(page, coremap_entry->page);
coremap_entry->owner->modified = 0;
}
coremap_entry->owner->inmemory = 0;
coremap_entry->owner->page = coremap_entry->page;
coremap_entry->owner->ondisk = 1;
}
// after this you can write over page, without loosing the old page.
if(swap_entry->ondisk){
read_page(page, swap_entry->page);
coremap_entry->page = swap_entry->page;
}
swap_entry->inmemory = 1;
swap_entry->page = page;
coremap_entry->owner = swap_entry;
return page;
}