linux-kernel - [PATCH 26/34] mm, vmscan: avoid passing in remaining unnecessarily to prepare_kswapd

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Date:	Fri,  8 Jul 2016 10:35:02 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>
Cc:	Rik van Riel <riel@...riel.com>, Vlastimil Babka <vbabka@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...hsingularity.net>
Subject: [PATCH 26/34] mm, vmscan: avoid passing in remaining unnecessarily to prepare_kswapd_sleep

As pointed out by Minchan Kim, the first call to prepare_kswapd_sleep
always passes in 0 for remaining and the second call can trivially
check the parameter in advance.

Suggested-by: Minchan Kim <minchan@...nel.org>
Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
---
 mm/vmscan.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6d5c78e2312b..8a67aa53aa7b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3020,15 +3020,10 @@ static bool zone_balanced(struct zone *zone, int order, int classzone_idx)
  *
  * Returns true if kswapd is ready to sleep
  */
-static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
-					int classzone_idx)
+static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, int classzone_idx)
 {
 	int i;
 
-	/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
-	if (remaining)
-		return false;
-
 	/*
 	 * The throttled processes are normally woken up in balance_pgdat() as
 	 * soon as pfmemalloc_watermark_ok() is true. But there is a potential
@@ -3243,7 +3238,7 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_o
 	prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
 
 	/* Try to sleep for a short interval */
-	if (prepare_kswapd_sleep(pgdat, reclaim_order, remaining, classzone_idx)) {
+	if (prepare_kswapd_sleep(pgdat, reclaim_order, classzone_idx)) {
 		/*
 		 * Compaction records what page blocks it recently failed to
 		 * isolate pages from and skips them in the future scanning.
@@ -3278,7 +3273,8 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_o
 	 * After a short sleep, check if it was a premature sleep. If not, then
 	 * go fully to sleep until explicitly woken up.
 	 */
-	if (prepare_kswapd_sleep(pgdat, reclaim_order, remaining, classzone_idx)) {
+	if (!remaining &&
+	    prepare_kswapd_sleep(pgdat, reclaim_order, classzone_idx)) {
 		trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
 
 		/*
-- 
2.6.4