linux-kernel - [PATCH v2 2/5] mm: workingset: #define radix entry eviction mask

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Date:	Fri, 29 Jan 2016 12:54:04 -0500
From:	Johannes Weiner <hannes@...xchg.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Vladimir Davydov <vdavydov@...tuozzo.com>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...com
Subject: [PATCH v2 2/5] mm: workingset: #define radix entry eviction mask

This is a compile-time constant, no need to calculate it on refault.

Signed-off-by: Johannes Weiner <hannes@...xchg.org>
Reviewed-by: Vladimir Davydov <vdavydov@...tuozzo.com>
---
 mm/workingset.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/mm/workingset.c b/mm/workingset.c
index 61ead9e..3ef92f6 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -152,6 +152,10 @@
  * refault distance will immediately activate the refaulting page.
  */
 
+#define EVICTION_SHIFT	(RADIX_TREE_EXCEPTIONAL_ENTRY + \
+			 ZONES_SHIFT + NODES_SHIFT)
+#define EVICTION_MASK	(~0UL >> EVICTION_SHIFT)
+
 static void *pack_shadow(unsigned long eviction, struct zone *zone)
 {
 	eviction = (eviction << NODES_SHIFT) | zone_to_nid(zone);
@@ -168,7 +172,6 @@ static void unpack_shadow(void *shadow,
 	unsigned long entry = (unsigned long)shadow;
 	unsigned long eviction;
 	unsigned long refault;
-	unsigned long mask;
 	int zid, nid;
 
 	entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT;
@@ -181,8 +184,7 @@ static void unpack_shadow(void *shadow,
 	*zone = NODE_DATA(nid)->node_zones + zid;
 
 	refault = atomic_long_read(&(*zone)->inactive_age);
-	mask = ~0UL >> (NODES_SHIFT + ZONES_SHIFT +
-			RADIX_TREE_EXCEPTIONAL_SHIFT);
+
 	/*
 	 * The unsigned subtraction here gives an accurate distance
 	 * across inactive_age overflows in most cases.
@@ -199,7 +201,7 @@ static void unpack_shadow(void *shadow,
 	 * inappropriate activation leading to pressure on the active
 	 * list is not a problem.
 	 */
-	*distance = (refault - eviction) & mask;
+	*distance = (refault - eviction) & EVICTION_MASK;
 }
 
 /**
-- 
2.7.0