LXR linux-bk/mm/swap.c

   1/*
   2 *  linux/mm/swap.c
   3 *
   4 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   5 */
   6
   7/*
   8 * This file contains the default values for the opereation of the
   9 * Linux VM subsystem. Fine-tuning documentation can be found in
  10 * linux/Documentation/sysctl/vm.txt.
  11 * Started 18.12.91
  12 * Swap aging added 23.2.95, Stephen Tweedie.
  13 * Buffermem limits added 12.3.98, Rik van Riel.
  14 */
  15
  16#include <linux/mm.h>
  17#include <linux/kernel_stat.h>
  18#include <linux/swap.h>
  19#include <linux/swapctl.h>
  20#include <linux/pagemap.h>
  21#include <linux/init.h>
  22
  23#include <asm/dma.h>
  24#include <asm/uaccess.h> /* for copy_to/from_user */
  25#include <asm/pgtable.h>
  26
  27/* How many pages do we try to swap or page in/out together? */
  28int page_cluster;
  29
  30pager_daemon_t pager_daemon = {
  31        512,    /* base number for calculating the number of tries */
  32        SWAP_CLUSTER_MAX,       /* minimum number of tries */
  33        8,      /* do swap I/O in clusters of this size */
  34};
  35
  36/*
  37 * Move an inactive page to the active list.
  38 */
  39static inline void activate_page_nolock(struct page * page)
  40{
  41        if (PageLRU(page) && !PageActive(page)) {
  42                del_page_from_inactive_list(page);
  43                add_page_to_active_list(page);
  44                KERNEL_STAT_INC(pgactivate);
  45        }
  46}
  47
  48void activate_page(struct page * page)
  49{
  50        spin_lock(&pagemap_lru_lock);
  51        activate_page_nolock(page);
  52        spin_unlock(&pagemap_lru_lock);
  53}
  54
  55/**
  56 * lru_cache_add: add a page to the page lists
  57 * @page: the page to add
  58 */
  59void lru_cache_add(struct page * page)
  60{
  61        if (!TestSetPageLRU(page)) {
  62                spin_lock(&pagemap_lru_lock);
  63                add_page_to_inactive_list(page);
  64                spin_unlock(&pagemap_lru_lock);
  65        }
  66}
  67
  68/**
  69 * __lru_cache_del: remove a page from the page lists
  70 * @page: the page to add
  71 *
  72 * This function is for when the caller already holds
  73 * the pagemap_lru_lock.
  74 */
  75void __lru_cache_del(struct page * page)
  76{
  77        if (TestClearPageLRU(page)) {
  78                if (PageActive(page)) {
  79                        del_page_from_active_list(page);
  80                } else {
  81                        del_page_from_inactive_list(page);
  82                }
  83        }
  84}
  85
  86/**
  87 * lru_cache_del: remove a page from the page lists
  88 * @page: the page to remove
  89 */
  90void lru_cache_del(struct page * page)
  91{
  92        spin_lock(&pagemap_lru_lock);
  93        __lru_cache_del(page);
  94        spin_unlock(&pagemap_lru_lock);
  95}
  96
  97/*
  98 * Perform any setup for the swap system
  99 */
 100void __init swap_setup(void)
 101{
 102        unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
 103
 104        /* Use a smaller cluster for small-memory machines */
 105        if (megs < 16)
 106                page_cluster = 2;
 107        else
 108                page_cluster = 3;
 109        /*
 110         * Right now other parts of the system means that we
 111         * _really_ don't want to cluster much more
 112         */
 113}
 114