linux-kernel - [patch 4/7] mm: vmscan: improve comment on low-page cache handling

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Message-Id: <1355767957-4913-5-git-send-email-hannes@cmpxchg.org>
Date:	Mon, 17 Dec 2012 13:12:34 -0500
From:	Johannes Weiner <hannes@...xchg.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Rik van Riel <riel@...hat.com>, Michal Hocko <mhocko@...e.cz>,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	Satoru Moriya <satoru.moriya@....com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [patch 4/7] mm: vmscan: improve comment on low-page cache handling

Fix comment style and elaborate on why anonymous memory is
force-scanned when file cache runs low.

Signed-off-by: Johannes Weiner <hannes@...xchg.org>
Reviewed-by: Rik van Riel <riel@...hat.com>
Acked-by: Mel Gorman <mgorman@...e.de>
Reviewed-by: Michal Hocko <mhocko@...e.cz>
---
 mm/vmscan.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index c37deaf..510c0d3 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1701,13 +1701,15 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
 	file  = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
 		get_lru_size(lruvec, LRU_INACTIVE_FILE);
 
+	/*
+	 * If it's foreseeable that reclaiming the file cache won't be
+	 * enough to get the zone back into a desirable shape, we have
+	 * to swap.  Better start now and leave the - probably heavily
+	 * thrashing - remaining file pages alone.
+	 */
 	if (global_reclaim(sc)) {
-		free  = zone_page_state(zone, NR_FREE_PAGES);
+		free = zone_page_state(zone, NR_FREE_PAGES);
 		if (unlikely(file + free <= high_wmark_pages(zone))) {
-			/*
-			 * If we have very few page cache pages, force-scan
-			 * anon pages.
-			 */
 			fraction[0] = 1;
 			fraction[1] = 0;
 			denominator = 1;
-- 
1.7.11.7

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