mm: add free_hot_cold_page_list() helper

This patch adds helper free_hot_cold_page_list() to free list of 0-order
pages. It frees pages directly from list without temporary page-vector.
It also calls trace_mm_pagevec_free() to simulate pagevec_free()
behaviour.

bloat-o-meter:

add/remove: 1/1 grow/shrink: 1/3 up/down: 267/-295 (-28)
function old new delta
free_hot_cold_page_list - 264 +264
get_page_from_freelist 2129 2132 +3
__pagevec_free 243 239 -4
split_free_page 380 373 -7
release_pages 606 510 -96
free_page_list 188 - -188

Signed-off-by: Konstantin Khlebnikov <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: KOSAKI Motohiro <[e-mail]>
Acked-by: Minchan Kim <[e-mail]>
Acked-by: Hugh Dickins <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/gfp.h

···
 extern void __free_pages(struct page *page, unsigned int order);
 extern void free_pages(unsigned long addr, unsigned int order);
 extern void free_hot_cold_page(struct page *page, int cold);
+extern void free_hot_cold_page_list(struct list_head *list, int cold);
 
 #define __free_page(page) __free_pages((page), 0)
 #define free_page(addr) free_pages((addr), 0)

mm/page_alloc.c

···
 }
 
 /*
+ * Free a list of 0-order pages
+ */
+void free_hot_cold_page_list(struct list_head *list, int cold)
+{
+	struct page *page, *next;
+
+	list_for_each_entry_safe(page, next, list, lru) {
+		trace_mm_pagevec_free(page, cold);
+		free_hot_cold_page(page, cold);
+	}
+}
+
+/*
  * split_page takes a non-compound higher-order page, and splits it into
  * n (1<<order) sub-pages: page[0..n]
  * Each sub-page must be freed individually.

mm/swap.c

···
 void release_pages(struct page **pages, int nr, int cold)
 {
 	int i;
-	struct pagevec pages_to_free;
+	LIST_HEAD(pages_to_free);
 	struct zone *zone = NULL;
 	unsigned long uninitialized_var(flags);
 
-	pagevec_init(&pages_to_free, cold);
 	for (i = 0; i < nr; i++) {
 		struct page *page = pages[i];
 
···
 			del_page_from_lru(zone, page);
 		}
 
-		if (!pagevec_add(&pages_to_free, page)) {
-			if (zone) {
-				spin_unlock_irqrestore(&zone->lru_lock, flags);
-				zone = NULL;
-			}
-			__pagevec_free(&pages_to_free);
-			pagevec_reinit(&pages_to_free);
-  		}
+		list_add(&page->lru, &pages_to_free);
 	}
 	if (zone)
 		spin_unlock_irqrestore(&zone->lru_lock, flags);
 
-	pagevec_free(&pages_to_free);
+	free_hot_cold_page_list(&pages_to_free, cold);
 }
 EXPORT_SYMBOL(release_pages);
 

mm/vmscan.c

···
 	return PAGEREF_RECLAIM;
 }
 
-static noinline_for_stack void free_page_list(struct list_head *free_pages)
-{
-	struct pagevec freed_pvec;
-	struct page *page, *tmp;
-
-	pagevec_init(&freed_pvec, 1);
-
-	list_for_each_entry_safe(page, tmp, free_pages, lru) {
-		list_del(&page->lru);
-		if (!pagevec_add(&freed_pvec, page)) {
-			__pagevec_free(&freed_pvec);
-			pagevec_reinit(&freed_pvec);
-		}
-	}
-
-	pagevec_free(&freed_pvec);
-}
-
 /*
  * shrink_page_list() returns the number of reclaimed pages
  */
···
 	if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
 		zone_set_flag(zone, ZONE_CONGESTED);
 
-	free_page_list(&free_pages);
+	free_hot_cold_page_list(&free_pages, 1);
 
 	list_splice(&ret_pages, page_list);
 	count_vm_events(PGACTIVATE, pgactivate);