The patch titled
Subject: maple_tree: add a fast path case in mas_wr_slot_store()
has been added to the -mm mm-unstable branch. Its filename is
maple_tree-add-a-fast-path-case-in-mas_wr_slot_store.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/maple_tree-add-a-fast-path-case-in-mas_wr_slot_store.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: Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx>
Subject: maple_tree: add a fast path case in mas_wr_slot_store()
Date: Wed, 28 Jun 2023 15:36:57 +0800
When expanding a range in two directions, only partially overwriting the
previous and next ranges, the number of entries will not be increased, so
we can just update the pivots as a fast path. However, it may introduce
potential risks in RCU mode, because it updates two pivots. We only
enable it in non-RCU mode.
Link: https://lkml.kernel.org/r/20230628073657.75314-5-zhangpeng.00@xxxxxxxxxxxxx
Signed-off-by: Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/maple_tree.c | 36 ++++++++++++++++++++++++------------
1 file changed, 24 insertions(+), 12 deletions(-)
--- a/lib/maple_tree.c~maple_tree-add-a-fast-path-case-in-mas_wr_slot_store
+++ a/lib/maple_tree.c
@@ -4167,23 +4167,35 @@ static inline bool mas_wr_slot_store(str
{
struct ma_state *mas = wr_mas->mas;
unsigned char offset = mas->offset;
+ void __rcu **slots = wr_mas->slots;
bool gap = false;
- if (wr_mas->offset_end - offset != 1)
- return false;
-
- gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset);
- gap |= !mt_slot_locked(mas->tree, wr_mas->slots, offset + 1);
+ gap |= !mt_slot_locked(mas->tree, slots, offset);
+ gap |= !mt_slot_locked(mas->tree, slots, offset + 1);
- if (mas->index == wr_mas->r_min) {
- /* Overwriting the range and over a part of the next range. */
- rcu_assign_pointer(wr_mas->slots[offset], wr_mas->entry);
- wr_mas->pivots[offset] = mas->last;
- } else {
- /* Overwriting a part of the range and over the next range */
- rcu_assign_pointer(wr_mas->slots[offset + 1], wr_mas->entry);
+ if (wr_mas->offset_end - offset == 1) {
+ if (mas->index == wr_mas->r_min) {
+ /* Overwriting the range and a part of the next one */
+ rcu_assign_pointer(slots[offset], wr_mas->entry);
+ wr_mas->pivots[offset] = mas->last;
+ } else {
+ /* Overwriting a part of the range and the next one */
+ rcu_assign_pointer(slots[offset + 1], wr_mas->entry);
+ wr_mas->pivots[offset] = mas->index - 1;
+ mas->offset++; /* Keep mas accurate. */
+ }
+ } else if (!mt_in_rcu(mas->tree)) {
+ /*
+ * Expand the range, only partially overwriting the previous and
+ * next ranges
+ */
+ gap |= !mt_slot_locked(mas->tree, slots, offset + 2);
+ rcu_assign_pointer(slots[offset + 1], wr_mas->entry);
wr_mas->pivots[offset] = mas->index - 1;
+ wr_mas->pivots[offset + 1] = mas->last;
mas->offset++; /* Keep mas accurate. */
+ } else {
+ return false;
}
trace_ma_write(__func__, mas, 0, wr_mas->entry);
_
Patches currently in -mm which might be from zhangpeng.00@xxxxxxxxxxxxx are
maple_tree-add-test-for-mas_wr_modify-fast-path.patch
maple_tree-add-test-for-expanding-range-in-rcu-mode.patch
maple_tree-optimize-mas_wr_append-also-improve-duplicating-vmas.patch
maple_tree-add-a-fast-path-case-in-mas_wr_slot_store.patch
