From:   skseofh@gmail.com
To:     akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Cc:     Daero Lee <skseofh@gmail.com>
Subject: [PATCH] mm/vmscan.c: no need to double-check if free pages are under high-watermark
Date:   Sun,  2 Jan 2022 12:31:29 +0900
Message-Id: <20220102033129.12913-1-skseofh@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
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From: Daero Lee <skseofh@gmail.com>

In kswapd_try_to_sleep function, to check whether kswapd can sleep,
the prepare_kswapd_sleep function is called twice.

If free pages are below high-watermark in the first call,
the @remaining variable is not updated at 0 and the
prepare_kswapd_sleep function is called for the second time.

I think it is necessary to set the initial value of the
@remaining to a non-zero value to prevent consecutive calls
to the same function.

Signed-off-by: Daero Lee <skseofh@gmail.com>
---
 mm/vmscan.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 700434db5735..1217ecec5bbb 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4331,7 +4331,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
 	/*
 	 * Return the order kswapd stopped reclaiming at as
 	 * prepare_kswapd_sleep() takes it into account. If another caller
-	 * entered the allocator slow path while kswapd was awake, order will
+	 * entered the allqocator slow path while kswapd was awake, order will
 	 * remain at the higher level.
 	 */
 	return sc.order;
@@ -4355,7 +4355,7 @@ static enum zone_type kswapd_highest_zoneidx(pg_data_t *pgdat,
 static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
 				unsigned int highest_zoneidx)
 {
-	long remaining = 0;
+	long remaining = ~0;
 	DEFINE_WAIT(wait);
 
 	if (freezing(current) || kthread_should_stop())
-- 
2.25.1