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The Committed_AS field can underflow in certain situations: > # while true; do cat /proc/meminfo | grep _AS; sleep 1; done | uniq -c > 1 Committed_AS: 18446744073709323392 kB > 11 Committed_AS: 18446744073709455488 kB > 6 Committed_AS: 35136 kB > 5 Committed_AS: 18446744073709454400 kB > 7 Committed_AS: 35904 kB > 3 Committed_AS: 18446744073709453248 kB > 2 Committed_AS: 34752 kB > 9 Committed_AS: 18446744073709453248 kB > 8 Committed_AS: 34752 kB > 3 Committed_AS: 18446744073709320960 kB > 7 Committed_AS: 18446744073709454080 kB > 3 Committed_AS: 18446744073709320960 kB > 5 Committed_AS: 18446744073709454080 kB > 6 Committed_AS: 18446744073709320960 kB Because NR_CPUS can be greater than 1000 and meminfo_proc_show() does not check for underflow. But NR_CPUS proportional isn't good calculation. In general, possibility of lock contention is proportional to the number of online cpus, not theorical maximum cpus (NR_CPUS). The current kernel has generic percpu-counter stuff. using it is right way. it makes code simplify and percpu_counter_read_positive() don't make underflow issue. Reported-by: Dave Hansen <dave@linux.vnet.ibm.com> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Eric B Munson <ebmunson@us.ibm.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: <stable@kernel.org> [All kernel versions] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
515 lines
13 KiB
C
515 lines
13 KiB
C
/*
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* linux/mm/swap.c
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*
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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*/
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/*
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* This file contains the default values for the operation of the
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* Linux VM subsystem. Fine-tuning documentation can be found in
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* Documentation/sysctl/vm.txt.
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* Started 18.12.91
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* Swap aging added 23.2.95, Stephen Tweedie.
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* Buffermem limits added 12.3.98, Rik van Riel.
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*/
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/kernel_stat.h>
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#include <linux/swap.h>
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#include <linux/mman.h>
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#include <linux/pagemap.h>
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#include <linux/pagevec.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/mm_inline.h>
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#include <linux/buffer_head.h> /* for try_to_release_page() */
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#include <linux/percpu_counter.h>
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#include <linux/percpu.h>
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#include <linux/cpu.h>
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#include <linux/notifier.h>
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#include <linux/backing-dev.h>
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#include <linux/memcontrol.h>
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#include "internal.h"
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/* How many pages do we try to swap or page in/out together? */
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int page_cluster;
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static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
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static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
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/*
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* This path almost never happens for VM activity - pages are normally
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* freed via pagevecs. But it gets used by networking.
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*/
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static void __page_cache_release(struct page *page)
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{
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if (PageLRU(page)) {
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unsigned long flags;
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struct zone *zone = page_zone(page);
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spin_lock_irqsave(&zone->lru_lock, flags);
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VM_BUG_ON(!PageLRU(page));
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__ClearPageLRU(page);
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del_page_from_lru(zone, page);
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spin_unlock_irqrestore(&zone->lru_lock, flags);
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}
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free_hot_page(page);
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}
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static void put_compound_page(struct page *page)
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{
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page = compound_head(page);
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if (put_page_testzero(page)) {
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compound_page_dtor *dtor;
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dtor = get_compound_page_dtor(page);
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(*dtor)(page);
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}
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}
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void put_page(struct page *page)
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{
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if (unlikely(PageCompound(page)))
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put_compound_page(page);
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else if (put_page_testzero(page))
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__page_cache_release(page);
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}
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EXPORT_SYMBOL(put_page);
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/**
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* put_pages_list() - release a list of pages
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* @pages: list of pages threaded on page->lru
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*
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* Release a list of pages which are strung together on page.lru. Currently
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* used by read_cache_pages() and related error recovery code.
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*/
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void put_pages_list(struct list_head *pages)
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{
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while (!list_empty(pages)) {
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struct page *victim;
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victim = list_entry(pages->prev, struct page, lru);
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list_del(&victim->lru);
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page_cache_release(victim);
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}
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}
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EXPORT_SYMBOL(put_pages_list);
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/*
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* pagevec_move_tail() must be called with IRQ disabled.
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* Otherwise this may cause nasty races.
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*/
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static void pagevec_move_tail(struct pagevec *pvec)
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{
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int i;
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int pgmoved = 0;
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struct zone *zone = NULL;
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for (i = 0; i < pagevec_count(pvec); i++) {
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struct page *page = pvec->pages[i];
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struct zone *pagezone = page_zone(page);
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if (pagezone != zone) {
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if (zone)
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spin_unlock(&zone->lru_lock);
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zone = pagezone;
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spin_lock(&zone->lru_lock);
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}
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if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
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int lru = page_is_file_cache(page);
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list_move_tail(&page->lru, &zone->lru[lru].list);
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pgmoved++;
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}
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}
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if (zone)
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spin_unlock(&zone->lru_lock);
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__count_vm_events(PGROTATED, pgmoved);
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release_pages(pvec->pages, pvec->nr, pvec->cold);
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pagevec_reinit(pvec);
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}
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/*
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* Writeback is about to end against a page which has been marked for immediate
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* reclaim. If it still appears to be reclaimable, move it to the tail of the
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* inactive list.
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*/
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void rotate_reclaimable_page(struct page *page)
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{
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if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
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!PageUnevictable(page) && PageLRU(page)) {
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struct pagevec *pvec;
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unsigned long flags;
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page_cache_get(page);
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local_irq_save(flags);
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pvec = &__get_cpu_var(lru_rotate_pvecs);
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if (!pagevec_add(pvec, page))
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pagevec_move_tail(pvec);
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local_irq_restore(flags);
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}
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}
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static void update_page_reclaim_stat(struct zone *zone, struct page *page,
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int file, int rotated)
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{
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struct zone_reclaim_stat *reclaim_stat = &zone->reclaim_stat;
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struct zone_reclaim_stat *memcg_reclaim_stat;
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memcg_reclaim_stat = mem_cgroup_get_reclaim_stat_from_page(page);
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reclaim_stat->recent_scanned[file]++;
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if (rotated)
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reclaim_stat->recent_rotated[file]++;
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if (!memcg_reclaim_stat)
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return;
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memcg_reclaim_stat->recent_scanned[file]++;
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if (rotated)
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memcg_reclaim_stat->recent_rotated[file]++;
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}
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/*
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* FIXME: speed this up?
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*/
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void activate_page(struct page *page)
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{
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struct zone *zone = page_zone(page);
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spin_lock_irq(&zone->lru_lock);
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if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
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int file = page_is_file_cache(page);
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int lru = LRU_BASE + file;
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del_page_from_lru_list(zone, page, lru);
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SetPageActive(page);
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lru += LRU_ACTIVE;
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add_page_to_lru_list(zone, page, lru);
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__count_vm_event(PGACTIVATE);
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update_page_reclaim_stat(zone, page, !!file, 1);
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}
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spin_unlock_irq(&zone->lru_lock);
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}
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/*
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* Mark a page as having seen activity.
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*
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* inactive,unreferenced -> inactive,referenced
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* inactive,referenced -> active,unreferenced
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* active,unreferenced -> active,referenced
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*/
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void mark_page_accessed(struct page *page)
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{
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if (!PageActive(page) && !PageUnevictable(page) &&
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PageReferenced(page) && PageLRU(page)) {
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activate_page(page);
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ClearPageReferenced(page);
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} else if (!PageReferenced(page)) {
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SetPageReferenced(page);
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}
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}
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EXPORT_SYMBOL(mark_page_accessed);
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void __lru_cache_add(struct page *page, enum lru_list lru)
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{
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struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru];
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page_cache_get(page);
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if (!pagevec_add(pvec, page))
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____pagevec_lru_add(pvec, lru);
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put_cpu_var(lru_add_pvecs);
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}
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/**
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* lru_cache_add_lru - add a page to a page list
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* @page: the page to be added to the LRU.
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* @lru: the LRU list to which the page is added.
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*/
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void lru_cache_add_lru(struct page *page, enum lru_list lru)
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{
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if (PageActive(page)) {
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VM_BUG_ON(PageUnevictable(page));
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ClearPageActive(page);
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} else if (PageUnevictable(page)) {
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VM_BUG_ON(PageActive(page));
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ClearPageUnevictable(page);
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}
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VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page));
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__lru_cache_add(page, lru);
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}
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/**
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* add_page_to_unevictable_list - add a page to the unevictable list
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* @page: the page to be added to the unevictable list
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*
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* Add page directly to its zone's unevictable list. To avoid races with
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* tasks that might be making the page evictable, through eg. munlock,
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* munmap or exit, while it's not on the lru, we want to add the page
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* while it's locked or otherwise "invisible" to other tasks. This is
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* difficult to do when using the pagevec cache, so bypass that.
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*/
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void add_page_to_unevictable_list(struct page *page)
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{
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struct zone *zone = page_zone(page);
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spin_lock_irq(&zone->lru_lock);
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SetPageUnevictable(page);
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SetPageLRU(page);
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add_page_to_lru_list(zone, page, LRU_UNEVICTABLE);
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spin_unlock_irq(&zone->lru_lock);
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}
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/*
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* Drain pages out of the cpu's pagevecs.
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* Either "cpu" is the current CPU, and preemption has already been
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* disabled; or "cpu" is being hot-unplugged, and is already dead.
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*/
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static void drain_cpu_pagevecs(int cpu)
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{
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struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu);
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struct pagevec *pvec;
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int lru;
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for_each_lru(lru) {
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pvec = &pvecs[lru - LRU_BASE];
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if (pagevec_count(pvec))
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____pagevec_lru_add(pvec, lru);
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}
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pvec = &per_cpu(lru_rotate_pvecs, cpu);
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if (pagevec_count(pvec)) {
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unsigned long flags;
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/* No harm done if a racing interrupt already did this */
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local_irq_save(flags);
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pagevec_move_tail(pvec);
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local_irq_restore(flags);
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}
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}
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void lru_add_drain(void)
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{
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drain_cpu_pagevecs(get_cpu());
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put_cpu();
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}
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static void lru_add_drain_per_cpu(struct work_struct *dummy)
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{
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lru_add_drain();
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}
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/*
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* Returns 0 for success
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*/
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int lru_add_drain_all(void)
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{
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return schedule_on_each_cpu(lru_add_drain_per_cpu);
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}
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/*
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* Batched page_cache_release(). Decrement the reference count on all the
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* passed pages. If it fell to zero then remove the page from the LRU and
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* free it.
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*
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* Avoid taking zone->lru_lock if possible, but if it is taken, retain it
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* for the remainder of the operation.
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*
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* The locking in this function is against shrink_inactive_list(): we recheck
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* the page count inside the lock to see whether shrink_inactive_list()
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* grabbed the page via the LRU. If it did, give up: shrink_inactive_list()
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* will free it.
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*/
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void release_pages(struct page **pages, int nr, int cold)
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{
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int i;
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struct pagevec pages_to_free;
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struct zone *zone = NULL;
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unsigned long uninitialized_var(flags);
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pagevec_init(&pages_to_free, cold);
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for (i = 0; i < nr; i++) {
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struct page *page = pages[i];
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if (unlikely(PageCompound(page))) {
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if (zone) {
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spin_unlock_irqrestore(&zone->lru_lock, flags);
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zone = NULL;
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}
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put_compound_page(page);
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continue;
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}
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if (!put_page_testzero(page))
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continue;
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if (PageLRU(page)) {
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struct zone *pagezone = page_zone(page);
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if (pagezone != zone) {
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if (zone)
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spin_unlock_irqrestore(&zone->lru_lock,
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flags);
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zone = pagezone;
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spin_lock_irqsave(&zone->lru_lock, flags);
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}
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VM_BUG_ON(!PageLRU(page));
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__ClearPageLRU(page);
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del_page_from_lru(zone, page);
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}
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if (!pagevec_add(&pages_to_free, page)) {
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if (zone) {
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spin_unlock_irqrestore(&zone->lru_lock, flags);
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zone = NULL;
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}
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__pagevec_free(&pages_to_free);
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pagevec_reinit(&pages_to_free);
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}
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}
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if (zone)
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spin_unlock_irqrestore(&zone->lru_lock, flags);
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pagevec_free(&pages_to_free);
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}
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/*
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* The pages which we're about to release may be in the deferred lru-addition
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* queues. That would prevent them from really being freed right now. That's
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* OK from a correctness point of view but is inefficient - those pages may be
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* cache-warm and we want to give them back to the page allocator ASAP.
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*
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* So __pagevec_release() will drain those queues here. __pagevec_lru_add()
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* and __pagevec_lru_add_active() call release_pages() directly to avoid
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* mutual recursion.
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*/
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void __pagevec_release(struct pagevec *pvec)
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{
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lru_add_drain();
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release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
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pagevec_reinit(pvec);
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}
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EXPORT_SYMBOL(__pagevec_release);
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/*
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* Add the passed pages to the LRU, then drop the caller's refcount
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* on them. Reinitialises the caller's pagevec.
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*/
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void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
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{
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int i;
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struct zone *zone = NULL;
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VM_BUG_ON(is_unevictable_lru(lru));
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for (i = 0; i < pagevec_count(pvec); i++) {
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struct page *page = pvec->pages[i];
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struct zone *pagezone = page_zone(page);
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int file;
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int active;
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if (pagezone != zone) {
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if (zone)
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spin_unlock_irq(&zone->lru_lock);
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zone = pagezone;
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spin_lock_irq(&zone->lru_lock);
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}
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VM_BUG_ON(PageActive(page));
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VM_BUG_ON(PageUnevictable(page));
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VM_BUG_ON(PageLRU(page));
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SetPageLRU(page);
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active = is_active_lru(lru);
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file = is_file_lru(lru);
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if (active)
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SetPageActive(page);
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update_page_reclaim_stat(zone, page, file, active);
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add_page_to_lru_list(zone, page, lru);
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}
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if (zone)
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spin_unlock_irq(&zone->lru_lock);
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release_pages(pvec->pages, pvec->nr, pvec->cold);
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pagevec_reinit(pvec);
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}
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EXPORT_SYMBOL(____pagevec_lru_add);
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/*
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* Try to drop buffers from the pages in a pagevec
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*/
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void pagevec_strip(struct pagevec *pvec)
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{
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int i;
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for (i = 0; i < pagevec_count(pvec); i++) {
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struct page *page = pvec->pages[i];
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if (page_has_private(page) && trylock_page(page)) {
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if (page_has_private(page))
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try_to_release_page(page, 0);
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unlock_page(page);
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}
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}
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}
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/**
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* pagevec_lookup - gang pagecache lookup
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* @pvec: Where the resulting pages are placed
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* @mapping: The address_space to search
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* @start: The starting page index
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* @nr_pages: The maximum number of pages
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*
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* pagevec_lookup() will search for and return a group of up to @nr_pages pages
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* in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
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* reference against the pages in @pvec.
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*
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* The search returns a group of mapping-contiguous pages with ascending
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* indexes. There may be holes in the indices due to not-present pages.
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*
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* pagevec_lookup() returns the number of pages which were found.
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*/
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unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
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pgoff_t start, unsigned nr_pages)
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{
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pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
|
|
return pagevec_count(pvec);
|
|
}
|
|
|
|
EXPORT_SYMBOL(pagevec_lookup);
|
|
|
|
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);
|
|
}
|
|
|
|
EXPORT_SYMBOL(pagevec_lookup_tag);
|
|
|
|
/*
|
|
* Perform any setup for the swap system
|
|
*/
|
|
void __init swap_setup(void)
|
|
{
|
|
unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
|
|
|
|
#ifdef CONFIG_SWAP
|
|
bdi_init(swapper_space.backing_dev_info);
|
|
#endif
|
|
|
|
/* 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
|
|
*/
|
|
}
|