linux-kernel - [PATCH 03/34] maple_tree: Avoid unnecessary ascending

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Message-Id: <20230425140955.3834476-4-Liam.Howlett@oracle.com>
Date:   Tue, 25 Apr 2023 10:09:24 -0400
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        maple-tree@...ts.infradead.org,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>
Subject: [PATCH 03/34] maple_tree: Avoid unnecessary ascending

The maple tree node limits are implied by the parent.  When walking up
the tree, the limit may not be known until a slot that does not have
implied limits are encountered.  However, if the node is the left-most
or right-most node, the walking up to find that limit can be skipped.

This commit also fixes the debug/testing code that was not setting the
limit on walking down the tree as that optimization is not compatible
with this change.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 lib/maple_tree.c                 | 6 ++++++
 tools/testing/radix-tree/maple.c | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index ac0245dd88dad..60bae5be008a6 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1132,6 +1132,12 @@ static int mas_ascend(struct ma_state *mas)
 		return 0;
 	}
 
+	if (!mas->min)
+		set_min = true;
+
+	if (mas->max == ULONG_MAX)
+		set_max = true;
+
 	min = 0;
 	max = ULONG_MAX;
 	do {
diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
index 9286d3baa12d6..75df543e019c9 100644
--- a/tools/testing/radix-tree/maple.c
+++ b/tools/testing/radix-tree/maple.c
@@ -35259,6 +35259,7 @@ static void mas_dfs_preorder(struct ma_state *mas)
 
 	struct maple_enode *prev;
 	unsigned char end, slot = 0;
+	unsigned long *pivots;
 
 	if (mas->node == MAS_START) {
 		mas_start(mas);
@@ -35291,6 +35292,9 @@ static void mas_dfs_preorder(struct ma_state *mas)
 		mas_ascend(mas);
 		goto walk_up;
 	}
+	pivots = ma_pivots(mte_to_node(prev), mte_node_type(prev));
+	mas->max = mas_safe_pivot(mas, pivots, slot, mte_node_type(prev));
+	mas->min = mas_safe_min(mas, pivots, slot);
 
 	return;
 done:
-- 
2.39.2