linux-kernel - [PATCH 12/12] maple_tree: mtree_range

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Date:   Wed,  1 Nov 2023 13:16:29 -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 12/12] maple_tree: mtree_range_walk() clean up

mtree_range_walk() needed to be updated to avoid checking if there was a
pivot value.  On closer examination, the code could avoid setting min or
max in certain scenarios.  The commit removes the extra check for
pivot[offset] before setting max and only sets max when necessary.  It
also only sets min if it is necessary by checking offset 0 prior to the
loop (as it has always done).

The commit also drops a dead node check since the end of the node will
return the array size when the last slot is occupied (by a potential
reuse in a dead node).  The data will be discarded later if the node is
marked dead.

Benchmarking these changes results in an increase in performance of
5.45% using the BENCH_WALK in the maple tree test code.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 lib/maple_tree.c | 27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index a91adaf17306..56cc8278260f 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -2796,32 +2796,29 @@ static inline void *mtree_range_walk(struct ma_state *mas)
 	min = mas->min;
 	max = mas->max;
 	do {
-		offset = 0;
 		last = next;
 		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;
-
-		if (pivots[offset] >= mas->index) {
-			prev_max = max;
-			prev_min = min;
-			max = pivots[offset];
+		prev_min = min;
+		prev_max = max;
+		if (pivots[0] >= mas->index) {
+			offset = 0;
+			max = pivots[0];
 			goto next;
 		}
 
-		do {
+		offset = 1;
+		while (offset < end) {
+			if (pivots[offset] >= mas->index) {
+				max = pivots[offset];
+				break;
+			}
 			offset++;
-		} while ((offset < end) && (pivots[offset] < mas->index));
+		}
 
-		prev_min = min;
 		min = pivots[offset - 1] + 1;
-		prev_max = max;
-		if (likely(offset < end && pivots[offset]))
-			max = pivots[offset];
-
 next:
 		slots = ma_slots(node, type);
 		next = mt_slot(mas->tree, slots, offset);
-- 
2.40.1