maple_tree: avoid checking other gaps after getting the largest gap

The last range stored in maple tree is typically quite large.  By checking
if it exceeds the sum of the remaining ranges in that node, it is possible
to avoid checking all other gaps.

Running the maple tree test suite in user mode almost always results in a
near 100% hit rate for this optimization.

Link: https://lkml.kernel.org/r/20231215074632.82045-1-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index c9a970e..6f241bb 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1518,6 +1518,9 @@ static unsigned long mas_leaf_max_gap(struct ma_state *mas)
                gap = ULONG_MAX - pivots[max_piv];
                if (gap > max_gap)
                        max_gap = gap;
+
+               if (max_gap > pivots[max_piv] - mas->min)
+                       return max_gap;
        }
 
        for (; i <= max_piv; i++) {