/*
* linux/mm/swap.c
*
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
*/
/*
* This file contains the default values for the opereation of the
* Linux VM subsystem. Fine-tuning documentation can be found in
* Documentation/sysctl/vm.txt.
* Started 18.12.91
* Swap aging added 23.2.95, Stephen Tweedie.
* Buffermem limits added 12.3.98, Rik van Riel.
*/
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mm_inline.h>
#include <linux/buffer_head.h> /* for try_to_release_page() */
#include <linux/module.h>
#include <linux/percpu_counter.h>
#include <linux/percpu.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/init.h>
/* How many pages do we try to swap or page in/out together? */
int page_cluster;
#ifdef CONFIG_HUGETLB_PAGE
void put_page(struct page *page)
{
if (unlikely(PageCompound(page))) {
page = (struct page *)page_private(page);
if (put_page_testzero(page)) {
void (*dtor)(struct page *page);
dtor = (void (*)(struct page *))page[1].mapping;
(*dtor)(page);
}
return;
}
if (put_page_testzero(page))
__page_cache_release(page);
}
EXPORT_SYMBOL(put_page);
#endif
/*
* Writeback is about to end against a page which has been marked for immediate
* reclaim. If it still appears to be reclaimable, move it to the tail of the
* inactive list. The page still has PageWriteback set, which will pin it.
*
* We don't expect many pages to come through here, so don't bother batching
* things up.
*
* To avoid placing the page at the tail of the LRU while PG_writeback is still
* set, this function will clear PG_writeback before performing the page
* motion. Do that inside the lru lock because once PG_writeback is cleared
* we may not touch the page.
*
* Returns zero if it cleared PG_writeback.
*/
int rotate_reclaimable_page(struct page *page)
{
struct zone *zone;
unsigned long flags;
if (PageLocked(page))
return 1;
if (PageDirty(page))
return 1;
if (PageActive(page))
return 1;
if (!PageLRU(page))
return 1;
zone = page_zone(page);
spin_lock_irqsave(&zone->lru_lock, flags);
if (PageLRU(page) && !PageActive(page)) {
list_del(&page->lru);
list_add_tail(&page->lru, &zone->inactive_list);
inc_page_state(pgrotated);
}
if (!test_clear_page_writeback(page))
BUG();
spin_unlock_irqrestore(&zone->lru_lock, flags);
return 0;
}
/*
* FIXME: speed this up?
*/
void fastcall activate_page(struct page *page)
{
struct zone *zone = page_zone(page);
spin_lock_irq(&zone->lru_lock);
if (PageLRU(page) && !PageActive(page)) {
del_page_from_inactive_list(zone, page);
SetPageActive(page);
add_page_to_active_list(zone, page);
inc_page_state(pgactivate);
}
spin_unlock_irq(&zone->lru_lock);
}
/*
* Mark a page as having seen activity.
*
* inactive,unreferenced -> inactive,referenced
* inactive,referenced -> active,unreferenced
* active,unreferenced -> active,referenced
*/
void fastcall mark_page_accessed(struct page *page)
{
if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
activate_page(page);
ClearPageReferenced(page);
} else if (!PageReferenced(page)) {
SetPageReferenced(page);
}
}
EXPORT_SYMBOL(mark_page_accessed);
/**
* lru_cache_add: add a page to the page lists
* @page: the page to add
*/
static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
void fastcall lru_cache_add(struct page *page)
{
struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
page_cache_get(page);
if (!pagevec_add(pvec, page))
__pagevec_lru_add(pvec);
put_cpu_var(lru_add_pvecs);
}
void fastcall lru_cache_add_active(struct page *page)
{
struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
page_cache_get(page);
if (!pagevec_add(pvec, page))
__pagevec_lru_add_active(pvec);
put_cpu_var(lru_add_active_pvecs);
}
void lru_add_drain(void)
{
struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
if (pagevec_count(pvec))
__pagevec_lru_add(pvec);
pvec = &__get_cpu_var(lru_add_active_pvecs);
if (pagevec_count(pvec))
__pagevec_lru_add_active(pvec);
put_cpu_var(lru_add_pvecs);
}
/*
* This path almost never happens for VM activity - pages are normally
* freed via pagevecs. But it gets used by networking.
*/
void fastcall __page_cache_release(struct page *page)
{
unsigned long flags;
struct zone *zone = page_zone(page);
spin_lock_irqsave(&zone->lru_lock, flags);
if (TestClearPageLRU(page))
del_page_from_lru(zone, page);
if (page_count(page) != 0)
page = NULL;
spin_unlock_irqrestore(&zone->lru_lock, flags);
if (page)
free_hot_page(page);
}
EXPORT_SYMBOL(__page_cache_release);
/*
* Batched page_cache_release(). Decrement the reference count on all the
* passed pages. If it fell to zero then remove the page from the LRU and
* free it.
*
* Avoid taking zone->lru_lock if possible, but if it is taken, retain it
* for the remainder of the operation.
*
* The locking in this function is against shrink_cache(): we recheck the
* page count inside the lock to see whether shrink_cache grabbed the page
* via the LRU. If it did, give up: shrink_cache will free it.
*/
void release_pages(struct page **pages, int nr, int cold)
{
int i;
struct pagevec pages_to_free;
struct zone *zone = NULL;
pagevec_init(&pages_to_free, cold);
for (i = 0; i < nr; i++) {
struct page *page = pages[i];
struct zone *pagezone;
if (!put_page_testzero(page))
continue;
pagezone = page_zone(page);
if (pagezone != zone) {
if (zone)
spin_unlock_irq(&zone->lru_lock);
zone = pagezone;
spin_lock_irq(&zone->lru_lock);
}
if (TestClearPageLRU(page))
del_page_from_lru(zone, page);
if (page_count(page) == 0) {
if (!pagevec_add(&pages_to_free, page)) {
spin_unlock_irq(&zone->lru_lock);
__pagevec_free(&pages_to_free);
pagevec_reinit(&pages_to_free);
zone = NULL; /* No lock is held */
}
}
}
if (zone)
spin_unlock_irq(&zone->lru_lock);
pagevec_free(&pages_to_free);
}
/*
* The pages which we're about to release may be in the deferred lru-addition
* queues. That would prevent them from really being freed right now. That's
* OK from a correctness point of view but is inefficient - those pages may be
* cache-warm and we want to give them back to the page allocator ASAP.
*
* So __pagevec_release() will drain those queues here. __pagevec_lru_add()
* and __pagevec_lru_add_active() call release_pages() directly to avoid
* mutual recursion.
*/
void __pagevec_release(struct pagevec *pvec)
{
lru_add_drain();
release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
pagevec_reinit(pvec);
}
/*
* pagevec_release() for pages which are known to not be on the LRU
*
* This function reinitialises the caller's pagevec.
*/
void __pagevec_release_nonlru(struct pagevec *pvec)
{
int i;
struct pagevec pages_to_free;
pagevec_init(&pages_to_free, pvec->cold);
pages_to_free.cold = pvec->cold;
for (i = 0; i < pagevec_count(pvec); i++) {
struct page *page = pvec->pages[i];
BUG_ON(PageLRU(page));
if (put_page_testzero(page))
pagevec_add(&pages_to_free, page);
}
pagevec_free(&pages_to_free);
pagevec_reinit(pvec);
}
/*
* Add the passed pages to the LRU, then drop the caller's refcount
* on them. Reinitialises the caller's pagevec.
*/
void __pagevec_lru_add(struct pagevec *pvec)
{
int i;
struct zone *zone = NULL;
for (i = 0; i < pagevec_count(pvec); i++) {
struct page *page = pvec->pages[i];
struct zone *pagezone = page_zone(page);
if (pagezone != zone) {
if (zone)
spin_unlock_irq(&zone->lru_lock);
zone = pagezone;
spin_lock_irq(&zone->lru_lock);
}
if (TestSetPageLRU(page))
BUG();
add_page_to_inactive_list(zone, page);
}
if (zone)
spin_unlock_irq(&zone->lru_lock);
release_pages(pvec->pages, pvec->nr, pvec->cold);
pagevec_reinit(pvec);
}
EXPORT_SYMBOL(__pagevec_lru_add);
void __pagevec_lru_add_active(struct pagevec *pvec)
{
int i;
struct zone *zone = NULL;
for (i = 0; i < pagevec_count(pvec); i++) {
struct page *page = pvec->pages[i];
struct zone *pagezone = page_zone(page);
if (pagezone != zone) {
if (zone)
spin_unlock_irq(&zone->lru_lock);
zone = pagezone;
spin_lock_irq(&zone->lru_lock);
}
if (TestSetPageLRU(page))
BUG();
if (TestSetPageActive(page))
BUG();
add_page_to_active_list(zone, page);
}
if (zone)
spin_unlock_irq(&zone->lru_lock);
release_pages(pvec->pages, pvec->nr, pvec->cold);
pagevec_reinit(pvec);
}
/*
* Try to drop buffers from the pages in a pagevec
*/
void pagevec_strip(struct pagevec *pvec)
{
int i;
for (i = 0; i < pagevec_count(pvec); i++) {
struct page *page = pvec->pages[i];
if (PagePrivate(page) && !TestSetPageLocked(page)) {
try_to_release_page(page, 0);
unlock_page(page);
}
}
}
/**
* pagevec_lookup - gang pagecache lookup
* @pvec: Where the resulting pages are placed
* @mapping: The address_space to search
* @start: The starting page index
* @nr_pages: The maximum number of pages
*
* pagevec_lookup() will search for and return a group of up to @nr_pages pages
* in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
* reference against the pages in @pvec.
*
* The search returns a group of mapping-contiguous pages with ascending
* indexes. There may be holes in the indices due to not-present pages.
*
* pagevec_lookup() returns the number of pages which were found.
*/
unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
pgoff_t start, unsigned nr_pages)
{
pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
return pagevec_count(pvec);
}
unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
pgoff_t *index, int tag, unsigned nr_pages)
{
pvec->nr = find_get_pages_tag(mapping, index, tag,
nr_pages, pvec->pages);
return pagevec_count(pvec);
}
#ifdef CONFIG_SMP
/*
* We tolerate a little inaccuracy to avoid ping-ponging the counter between
* CPUs
*/
#define ACCT_THRESHOLD max(16, NR_CPUS * 2)
static DEFINE_PER_CPU(long, committed_space) = 0;
void vm_acct_memory(long pages)
{
long *local;
preempt_disable();
local = &__get_cpu_var(committed_space);
*local += pages;
if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
atomic_add(*local, &vm_committed_space);
*local = 0;
}
preempt_enable();
}
EXPORT_SYMBOL(vm_acct_memory);
#ifdef CONFIG_HOTPLUG_CPU
static void lru_drain_cache(unsigned int cpu)
{
struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
/* CPU is dead, so no locking needed. */
if (pagevec_count(pvec))
__pagevec_lru_add(pvec);
pvec = &per_cpu(lru_add_active_pvecs, cpu);
if (pagevec_count(pvec))
__pagevec_lru_add_active(pvec);
}
/* Drop the CPU's cached committed space back into the central pool. */
static int cpu_swap_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
long *committed;
committed = &per_cpu(committed_space, (long)hcpu);
if (action == CPU_DEAD) {
atomic_add(*committed, &vm_committed_space);
*committed = 0;
lru_drain_cache((long)hcpu);
}
return NOTIFY_OK;
}
#endif /* CONFIG_HOTPLUG_CPU */
#endif /* CONFIG_SMP */
#ifdef CONFIG_SMP
void percpu_counter_mod(struct percpu_counter *fbc, long amount)
{
long count;
long *pcount;
int cpu = get_cpu();
pcount = per_cpu_ptr(fbc->counters, cpu);
count = *pcount + amount;
if (count >= FBC_BATCH || count <= -FBC_BATCH) {
spin_lock(&fbc->lock);
fbc->count += count;
spin_unlock(&fbc->lock);
count = 0;
}
*pcount = count;
put_cpu();
}
EXPORT_SYMBOL(percpu_counter_mod);
#endif
/*
* Perform any setup for the swap system
*/
void __init swap_setup(void)
{
unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
/* Use a smaller cluster for small-memory machines */
if (megs < 16)
page_cluster = 2;
else
page_cluster = 3;
/*
* Right now other parts of the system means that we
* _really_ don't want to cluster much more
*/
hotcpu_notifier(cpu_swap_callback, 0);
}
