vmscan: evict streaming IO first

Count the insertion of new pages in the statistics used to drive the
pageout scanning code.  This should help the kernel quickly evict
streaming file IO.

We count on the fact that new file pages start on the inactive file LRU
and new anonymous pages start on the active anon list.  This means
streaming file IO will increment the recent scanned file statistic, while
leaving the recent rotated file statistic alone, driving pageout scanning
to the file LRUs.

Pageout activity does its own list manipulation.
Signed-off-by: NRik van Riel <riel@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Tested-by: NGene Heskett <gene.heskett@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/swap.c

@@ -445,6 +445,7 @@ void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
 	for (i = 0; i < pagevec_count(pvec); i++) {
 		struct page *page = pvec->pages[i];
 		struct zone *pagezone = page_zone(page);
+		int file;
 
 		if (pagezone != zone) {
 			if (zone)
@@ -456,8 +457,12 @@ void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru)
 		VM_BUG_ON(PageUnevictable(page));
 		VM_BUG_ON(PageLRU(page));
 		SetPageLRU(page);
-		if (is_active_lru(lru))
+		file = is_file_lru(lru);
+		zone->recent_scanned[file]++;
+		if (is_active_lru(lru)) {
 			SetPageActive(page);
+			zone->recent_rotated[file]++;
+		}
 		add_page_to_lru_list(zone, page, lru);
 	}
 	if (zone)