linux-kernel - [PATCH 1/9] mm: vmscan: simplify nr

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Message-Id: <20201202182725.265020-2-shy828301@gmail.com>
Date:   Wed,  2 Dec 2020 10:27:17 -0800
From:   Yang Shi <shy828301@...il.com>
To:     guro@...com, ktkhai@...tuozzo.com, shakeelb@...gle.com,
        david@...morbit.com, hannes@...xchg.org, mhocko@...e.com,
        akpm@...ux-foundation.org
Cc:     shy828301@...il.com, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/9] mm: vmscan: simplify nr_deferred update code

Currently if (next_deferred - scanned) = 0, the code would just read the current
nr_deferred otherwise add the delta back.  Both needs atomic operation anyway, it
seems there is not too much gain by distinguishing the two cases, so just add the
delta back even though the delta is 0.  This would simply the code for the following
patches too.

Signed-off-by: Yang Shi <shy828301@...il.com>
---
 mm/vmscan.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7b4e31eac2cf..7d6186a07daf 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -528,14 +528,10 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
 		next_deferred = 0;
 	/*
 	 * move the unused scan count back into the shrinker in a
-	 * manner that handles concurrent updates. If we exhausted the
-	 * scan, there is no need to do an update.
+	 * manner that handles concurrent updates.
 	 */
-	if (next_deferred > 0)
-		new_nr = atomic_long_add_return(next_deferred,
-						&shrinker->nr_deferred[nid]);
-	else
-		new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
+	new_nr = atomic_long_add_return(next_deferred,
+					&shrinker->nr_deferred[nid]);
 
 	trace_mm_shrink_slab_end(shrinker, nid, freed, nr, new_nr, total_scan);
 	return freed;
-- 
2.26.2