linux-kernel - [PATCH 11/12] maple_tree: Don't find node end in mtree_lookup

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Date:   Wed,  1 Nov 2023 13:16:28 -0400
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>
Subject: [PATCH 11/12] maple_tree: Don't find node end in mtree_lookup_walk()

Since the pivot being set is now reliable, the optimized loop no longer
needs to find the node end.  The redundant check for a dead node can
also be avoided as there is no danger of using the wrong pivot since the
results will be thrown out in the case of a dead node by the later
check.

This patch also adds a benchmark test for the function to the maple tree
test framework.  The benchmark shows an average increase performance of
5.98% over 3 runs with this commit.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 lib/maple_tree.c      | 12 +++---------
 lib/test_maple_tree.c | 21 +++++++++++++++++++++
 2 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index e45734676471..a91adaf17306 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -3732,23 +3732,17 @@ static inline void *mtree_lookup_walk(struct ma_state *mas)
 	enum maple_type type;
 	void __rcu **slots;
 	unsigned char end;
-	unsigned long max;
 
 	next = mas->node;
-	max = ULONG_MAX;
 	do {
-		offset = 0;
 		node = mte_to_node(next);
 		type = mte_node_type(next);
 		pivots = ma_pivots(node, type);
-		end = ma_data_end(node, type, pivots, max);
-		if (unlikely(ma_dead_node(node)))
-			goto dead_node;
+		end = mt_pivots[type];
+		offset = 0;
 		do {
-			if (pivots[offset] >= mas->index) {
-				max = pivots[offset];
+			if (pivots[offset] >= mas->index)
 				break;
-			}
 		} while (++offset < end);
 
 		slots = ma_slots(node, type);
diff --git a/lib/test_maple_tree.c b/lib/test_maple_tree.c
index b82c02f15380..d36dc64a93e4 100644
--- a/lib/test_maple_tree.c
+++ b/lib/test_maple_tree.c
@@ -42,6 +42,7 @@ atomic_t maple_tree_tests_passed;
 /* #define BENCH_NODE_STORE */
 /* #define BENCH_AWALK */
 /* #define BENCH_WALK */
+/* #define BENCH_LOAD */
 /* #define BENCH_MT_FOR_EACH */
 /* #define BENCH_FORK */
 /* #define BENCH_MAS_FOR_EACH */
@@ -1753,6 +1754,19 @@ static noinline void __init bench_walk(struct maple_tree *mt)
 }
 #endif
 
+#if defined(BENCH_LOAD)
+static noinline void __init bench_load(struct maple_tree *mt)
+{
+	int i, max = 2500, count = 550000000;
+
+	for (i = 0; i < max; i += 10)
+		mtree_store_range(mt, i, i + 5, xa_mk_value(i), GFP_KERNEL);
+
+	for (i = 0; i < count; i++)
+		mtree_load(mt, 1470);
+}
+#endif
+
 #if defined(BENCH_MT_FOR_EACH)
 static noinline void __init bench_mt_for_each(struct maple_tree *mt)
 {
@@ -3606,6 +3620,13 @@ static int __init maple_tree_seed(void)
 	mtree_destroy(&tree);
 	goto skip;
 #endif
+#if defined(BENCH_LOAD)
+#define BENCH
+	mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE);
+	bench_load(&tree);
+	mtree_destroy(&tree);
+	goto skip;
+#endif
 #if defined(BENCH_FORK)
 #define BENCH
 	mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE);
-- 
2.40.1