+ maple_tree-optimise-mas_wr_node_store-when-not-in-rcu-mode.patch added to mm-unstable branch

The patch titled
     Subject: maple_tree: optimise mas_wr_node_store() when not in rcu mode
has been added to the -mm mm-unstable branch.  Its filename is
     maple_tree-optimise-mas_wr_node_store-when-not-in-rcu-mode.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/maple_tree-optimise-mas_wr_node_store-when-not-in-rcu-mode.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Liam R. Howlett (Oracle)" <[email protected]>
Subject: maple_tree: optimise mas_wr_node_store() when not in rcu mode
Date: Fri, 21 Aug 2026 15:26:17 -0400

Clearing the entire node on the stack is unnecessary since most of the
node will be overwritten anyways.  Just clear what isn't used after the
data is in place.

Benchmarking shows a speedup of 0.67% on a height 4 tree with 2048
entries.

Link: https://lore.kernel.org/[email protected]
Signed-off-by: Liam R. Howlett (Oracle) <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Breno Leitao <[email protected]>
Cc: Chris Mason <[email protected]>
Cc: Chuck Lever <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Waiman Long <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 lib/maple_tree.c |   20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

--- a/lib/maple_tree.c~maple_tree-optimise-mas_wr_node_store-when-not-in-rcu-mode
+++ a/lib/maple_tree.c
@@ -3187,7 +3187,7 @@ static void mas_wr_spanning_store(struct
 static inline void mas_wr_node_store(struct ma_wr_state *wr_mas)
 {
 	unsigned char dst_offset, offset_end;
-	unsigned char copy_size, node_pivots;
+	unsigned char copy_size, node_pivots, node_slots;
 	struct maple_node reuse, *newnode;
 	unsigned long *dst_pivots;
 	void __rcu **dst_slots;
@@ -3200,6 +3200,7 @@ static inline void mas_wr_node_store(str
 	in_rcu = mt_in_rcu(mas->tree);
 	offset_end = wr_mas->offset_end;
 	node_pivots = mt_pivots[wr_mas->type];
+	node_slots = mt_slots[wr_mas->type];
 	/* Assume last adds an entry */
 	new_end = mas->end + 1 - offset_end + mas->offset;
 	if (mas->last == wr_mas->end_piv) {
@@ -3211,7 +3212,6 @@ static inline void mas_wr_node_store(str
 	if (in_rcu) {
 		newnode = mas_pop_node(mas);
 	} else {
-		memset(&reuse, 0, sizeof(struct maple_node));
 		newnode = &reuse;
 	}
 
@@ -3255,7 +3255,21 @@ static inline void mas_wr_node_store(str
 		dst_pivots[new_end] = mas->max;
 
 done:
-	mas_leaf_set_meta(newnode, maple_leaf_64, new_end);
+	if (!in_rcu && new_end + 2 < node_slots) {
+		unsigned char clear_from = new_end + 1;
+
+		/*
+		 * Note that the last slot is never cleared, since the metadata
+		 * will be stored there or it has a value.
+		 */
+		memset(dst_slots + clear_from, 0,
+		       sizeof(void __rcu *) * (node_slots - clear_from));
+		if (clear_from < node_pivots)
+			memset(dst_pivots + clear_from, 0,
+			       sizeof(unsigned long) * (node_pivots - clear_from));
+	}
+
+	mas_leaf_set_meta(newnode, wr_mas->type, new_end);
 	if (in_rcu) {
 		struct maple_enode *old_enode = mas->node;
 
_

Patches currently in -mm which might be from [email protected] are

maple_tree-add-rcu-locking-check-when-lockdep-is-enabled.patch
locking-lockdep-add-sequence-counter-to-held_lock.patch
maple_tree-add-write-lock-checking-with-lockdep-sequence-numbers.patch
maple_tree-documentation-fix.patch
maple_tree-drop-dead-code-from-mas_extend_spanning_null.patch
maple_tree-drop-maple_alloc_slots.patch
maple_tree-clarify-comments-on-mas_nomem.patch
maple_tree-use-prefetched-value-in-mas_wr_store_type.patch
maple_tree-optimise-mas_wr_node_store-when-not-in-rcu-mode.patch
maple_tree-micro-optimisation-of-mas_wr_store_type.patch
maple_tree-add-bulk-parent-set-helper.patch
maple_tree-catch-race-in-mas_alloc_cyclic.patch
maple_tree-document-that-erase-may-use-gfp_kernel-for-allocations.patch
maple_tree-avoid-mas_erase-and-mtree_erase-failures.patch
maple_tree-document-erase-and-allocations-better.patch
maple_tree-change-two-gfp-flags-in-tests.patch
maple_tree-fix-argument-name-in-header.patch
maple_tree-avoid-extra-gap-calculation.patch
maple_tree-add-helper-mas_make_walkable.patch