linux-kernel - Re: [PATCH 2/2] memcg, vmscan: Fix forced scan of anonymous pages

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Message-ID: <20140801184525.GK9952@cmpxchg.org>
Date:	Fri, 1 Aug 2014 14:45:25 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Jerome Marchand <jmarchan@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 2/2] memcg, vmscan: Fix forced scan of anonymous pages

On Thu, Jul 31, 2014 at 02:30:26PM +0200, Michal Hocko wrote:
> On Thu 31-07-14 13:49:45, Jerome Marchand wrote:
> > @@ -1950,8 +1950,11 @@ static void get_scan_count(struct lruvec *lruvec, int swappiness,
> >  	 */
> >  	if (global_reclaim(sc)) {
> >  		unsigned long free = zone_page_state(zone, NR_FREE_PAGES);
> > +		unsigned long zonefile =
> > +			zone_page_state(zone, NR_LRU_BASE + LRU_ACTIVE_FILE) +
> > +			zone_page_state(zone, NR_LRU_BASE + LRU_INACTIVE_FILE);
> >  
> > -		if (unlikely(file + free <= high_wmark_pages(zone))) {
> > +		if (unlikely(zonefile + free <= high_wmark_pages(zone))) {
> >  			scan_balance = SCAN_ANON;
> >  			goto out;
> >  		}
> 
> You could move file and anon further down when we actually use them.

Agreed with that.  Can we merge this into the original patch?

---
>From e49bef8d2751d9b27f1733e3e0eced325ffce700 Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@...xchg.org>
Date: Fri, 1 Aug 2014 10:48:26 -0400
Subject: [patch] memcg, vmscan: Fix forced scan of anonymous pages fix -
 cleanups

o Use enum zone_stat_item symbols directly to select zone stats,
  rather than NR_LRU_BASE plus LRU index

o scanned/rotated scaling is the only user of the lruvec anon/file
  counters, so move the reads of those values to right before that

Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
 mm/vmscan.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index b3f629bdf4fe..2836b5373b2e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1934,11 +1934,6 @@ static void get_scan_count(struct lruvec *lruvec, int swappiness,
 		goto out;
 	}
 
-	anon  = get_lru_size(lruvec, LRU_ACTIVE_ANON) +
-		get_lru_size(lruvec, LRU_INACTIVE_ANON);
-	file  = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
-		get_lru_size(lruvec, LRU_INACTIVE_FILE);
-
 	/*
 	 * Prevent the reclaimer from falling into the cache trap: as
 	 * cache pages start out inactive, every cache fault will tip
@@ -1949,12 +1944,14 @@ static void get_scan_count(struct lruvec *lruvec, int swappiness,
 	 * anon pages.  Try to detect this based on file LRU size.
 	 */
 	if (global_reclaim(sc)) {
-		unsigned long free = zone_page_state(zone, NR_FREE_PAGES);
-		unsigned long zonefile =
-			zone_page_state(zone, NR_LRU_BASE + LRU_ACTIVE_FILE) +
-			zone_page_state(zone, NR_LRU_BASE + LRU_INACTIVE_FILE);
+		unsigned long zonefile;
+		unsigned long zonefree;
+
+		zonefree = zone_page_state(zone, NR_FREE_PAGES);
+		zonefile = zone_page_state(zone, NR_ACTIVE_FILE) +
+			   zone_page_state(zone, NR_INACTIVE_FILE);
 
-		if (unlikely(zonefile + free <= high_wmark_pages(zone))) {
+		if (unlikely(zonefile + zonefree <= high_wmark_pages(zone))) {
 			scan_balance = SCAN_ANON;
 			goto out;
 		}
@@ -1989,6 +1986,12 @@ static void get_scan_count(struct lruvec *lruvec, int swappiness,
 	 *
 	 * anon in [0], file in [1]
 	 */
+
+	anon  = get_lru_size(lruvec, LRU_ACTIVE_ANON) +
+		get_lru_size(lruvec, LRU_INACTIVE_ANON);
+	file  = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
+		get_lru_size(lruvec, LRU_INACTIVE_FILE);
+
 	spin_lock_irq(&zone->lru_lock);
 	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
 		reclaim_stat->recent_scanned[0] /= 2;
-- 
2.0.3

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