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authorRik van Riel <riel@redhat.com>2008-10-18 20:26:35 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-20 08:50:25 -0700
commit7e9cd484204f9e5b316ed35b241abf088d76e0af (patch)
tree79f2567e7bb96af2d97d8d5407cc990e26eda95c /mm/vmscan.c
parentvmscan: second chance replacement for anonymous pages (diff)
downloadlinux-dev-7e9cd484204f9e5b316ed35b241abf088d76e0af.tar.xz
linux-dev-7e9cd484204f9e5b316ed35b241abf088d76e0af.zip
vmscan: fix pagecache reclaim referenced bit check
Moving referenced pages back to the head of the active list creates a huge scalability problem, because by the time a large memory system finally runs out of free memory, every single page in the system will have been referenced. Not only do we not have the time to scan every single page on the active list, but since they have will all have the referenced bit set, that bit conveys no useful information. A more scalable solution is to just move every page that hits the end of the active list to the inactive list. We clear the referenced bit off of mapped pages, which need just one reference to be moved back onto the active list. Unmapped pages will be moved back to the active list after two references (see mark_page_accessed). We preserve the PG_referenced flag on unmapped pages to preserve accesses that were made while the page was on the active list. Signed-off-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to '')
-rw-r--r--mm/vmscan.c45
1 files changed, 13 insertions, 32 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c82ee9a33cfc..9588973849d0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1064,7 +1064,6 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
int pgdeactivate = 0;
unsigned long pgscanned;
LIST_HEAD(l_hold); /* The pages which were snipped off */
- LIST_HEAD(l_active);
LIST_HEAD(l_inactive);
struct page *page;
struct pagevec pvec;
@@ -1095,21 +1094,28 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
cond_resched();
page = lru_to_page(&l_hold);
list_del(&page->lru);
+
+ /* page_referenced clears PageReferenced */
+ if (page_mapping_inuse(page) &&
+ page_referenced(page, 0, sc->mem_cgroup))
+ pgmoved++;
+
list_add(&page->lru, &l_inactive);
}
/*
- * Count the referenced pages as rotated, even when they are moved
- * to the inactive list. This helps balance scan pressure between
- * file and anonymous pages in get_scan_ratio.
- */
+ * Count referenced pages from currently used mappings as
+ * rotated, even though they are moved to the inactive list.
+ * This helps balance scan pressure between file and anonymous
+ * pages in get_scan_ratio.
+ */
zone->recent_rotated[!!file] += pgmoved;
/*
- * Now put the pages back on the appropriate [file or anon] inactive
- * and active lists.
+ * Move the pages to the [file or anon] inactive list.
*/
pagevec_init(&pvec, 1);
+
pgmoved = 0;
lru = LRU_BASE + file * LRU_FILE;
spin_lock_irq(&zone->lru_lock);
@@ -1142,31 +1148,6 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
pagevec_strip(&pvec);
spin_lock_irq(&zone->lru_lock);
}
-
- pgmoved = 0;
- lru = LRU_ACTIVE + file * LRU_FILE;
- while (!list_empty(&l_active)) {
- page = lru_to_page(&l_active);
- prefetchw_prev_lru_page(page, &l_active, flags);
- VM_BUG_ON(PageLRU(page));
- SetPageLRU(page);
- VM_BUG_ON(!PageActive(page));
-
- list_move(&page->lru, &zone->lru[lru].list);
- mem_cgroup_move_lists(page, true);
- pgmoved++;
- if (!pagevec_add(&pvec, page)) {
- __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
- pgmoved = 0;
- spin_unlock_irq(&zone->lru_lock);
- if (vm_swap_full())
- pagevec_swap_free(&pvec);
- __pagevec_release(&pvec);
- spin_lock_irq(&zone->lru_lock);
- }
- }
- __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
-
__count_zone_vm_events(PGREFILL, zone, pgscanned);
__count_vm_events(PGDEACTIVATE, pgdeactivate);
spin_unlock_irq(&zone->lru_lock);