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![Lee Schermerhorn](/assets/img/avatar_default.png)
In the fault paths that install new anonymous pages, check whether the page is evictable or not using lru_cache_add_active_or_unevictable(). If the page is evictable, just add it to the active lru list [via the pagevec cache], else add it to the unevictable list. This "proactive" culling in the fault path mimics the handling of mlocked pages in Nick Piggin's series to keep mlocked pages off the lru lists. Notes: 1) This patch is optional--e.g., if one is concerned about the additional test in the fault path. We can defer the moving of nonreclaimable pages until when vmscan [shrink_*_list()] encounters them. Vmscan will only need to handle such pages once, but if there are a lot of them it could impact system performance. 2) The 'vma' argument to page_evictable() is require to notice that we're faulting a page into an mlock()ed vma w/o having to scan the page's rmap in the fault path. Culling mlock()ed anon pages is currently the only reason for this patch. 3) We can't cull swap pages in read_swap_cache_async() because the vma argument doesn't necessarily correspond to the swap cache offset passed in by swapin_readahead(). This could [did!] result in mlocking pages in non-VM_LOCKED vmas if [when] we tried to cull in this path. 4) Move set_pte_at() to after where we add page to lru to keep it hidden from other tasks that might walk the page table. We already do it in this order in do_anonymous() page. And, these are COW'd anon pages. Is this safe? [riel@redhat.com: undo an overzealous code cleanup] Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com> Signed-off-by: Rik van Riel <riel@redhat.com> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
614 lines
15 KiB
C
614 lines
15 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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/*
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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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mem_cgroup_move_lists(page, lru);
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zone->recent_rotated[!!file]++;
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zone->recent_scanned[!!file]++;
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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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* lru_cache_add_active_or_unevictable
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* @page: the page to be added to LRU
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* @vma: vma in which page is mapped for determining reclaimability
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*
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* place @page on active or unevictable LRU list, depending on
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* page_evictable(). Note that if the page is not evictable,
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* it goes directly back onto it's zone's unevictable list. It does
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* NOT use a per cpu pagevec.
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*/
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void lru_cache_add_active_or_unevictable(struct page *page,
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struct vm_area_struct *vma)
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{
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if (page_evictable(page, vma))
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lru_cache_add_lru(page, LRU_ACTIVE + page_is_file_cache(page));
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else
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add_page_to_unevictable_list(page);
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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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#if defined(CONFIG_NUMA) || defined(CONFIG_UNEVICTABLE_LRU)
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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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#else
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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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lru_add_drain();
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return 0;
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}
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#endif
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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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* pagevec_release() for pages which are known to not be on the LRU
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*
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* This function reinitialises the caller's pagevec.
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*/
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void __pagevec_release_nonlru(struct pagevec *pvec)
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{
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int i;
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struct pagevec pages_to_free;
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pagevec_init(&pages_to_free, pvec->cold);
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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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VM_BUG_ON(PageLRU(page));
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if (put_page_testzero(page))
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pagevec_add(&pages_to_free, page);
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}
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pagevec_free(&pages_to_free);
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pagevec_reinit(pvec);
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}
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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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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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if (is_active_lru(lru))
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SetPageActive(page);
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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++) {
|
|
struct page *page = pvec->pages[i];
|
|
|
|
if (PagePrivate(page) && trylock_page(page)) {
|
|
if (PagePrivate(page))
|
|
try_to_release_page(page, 0);
|
|
unlock_page(page);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* pagevec_swap_free - try to free swap space from the pages in a pagevec
|
|
* @pvec: pagevec with swapcache pages to free the swap space of
|
|
*
|
|
* The caller needs to hold an extra reference to each page and
|
|
* not hold the page lock on the pages. This function uses a
|
|
* trylock on the page lock so it may not always free the swap
|
|
* space associated with a page.
|
|
*/
|
|
void pagevec_swap_free(struct pagevec *pvec)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < pagevec_count(pvec); i++) {
|
|
struct page *page = pvec->pages[i];
|
|
|
|
if (PageSwapCache(page) && trylock_page(page)) {
|
|
if (PageSwapCache(page))
|
|
remove_exclusive_swap_page_ref(page);
|
|
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);
|
|
}
|
|
|
|
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);
|
|
|
|
#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);
|
|
|
|
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_long_add(*local, &vm_committed_space);
|
|
*local = 0;
|
|
}
|
|
preempt_enable();
|
|
}
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
|
|
/* 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 || action == CPU_DEAD_FROZEN) {
|
|
atomic_long_add(*committed, &vm_committed_space);
|
|
*committed = 0;
|
|
drain_cpu_pagevecs((long)hcpu);
|
|
}
|
|
return NOTIFY_OK;
|
|
}
|
|
#endif /* CONFIG_HOTPLUG_CPU */
|
|
#endif /* CONFIG_SMP */
|
|
|
|
/*
|
|
* 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
|
|
*/
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
hotcpu_notifier(cpu_swap_callback, 0);
|
|
#endif
|
|
}
|