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Subject[PATCH 07/13] lib/generic-radix-tree: Optimise __genradix_iter_peek()
Date
Use the the 'shift' rather than the 'level'.
NB There are exactly zero users of this code.

Signed-off-by: David Laight <david.laight@aculab.com>
---
lib/generic-radix-tree.c | 24 ++++++++----------------
1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c
index 219b43250a06..0df99ee428d8 100644
--- a/lib/generic-radix-tree.c
+++ b/lib/generic-radix-tree.c
@@ -22,14 +22,6 @@ static inline int genradix_depth_shift(unsigned depth)
return PAGE_SHIFT + GENRADIX_ARY_SHIFT * depth;
}

-/*
- * Returns size (of data, in bytes) that a tree of a given depth holds:
- */
-static inline size_t genradix_depth_size(unsigned depth)
-{
- return 1UL << genradix_depth_shift(depth);
-}
-
/*
* The 'depth' of the tree is held in the low bits of the 'root'.
* Since all the buffers are allocated as pages lots of low bits are zero.
@@ -209,7 +201,7 @@ void *__genradix_iter_peek(struct genradix_iter *iter,
{
struct genradix_root *r;
struct genradix_node *n;
- unsigned level, i;
+ unsigned int shift, level, i;
restart:
r = READ_ONCE(radix->root);
if (!r)
@@ -217,21 +209,21 @@ void *__genradix_iter_peek(struct genradix_iter *iter,

n = genradix_root_to_node(r);
level = genradix_root_to_depth(r);
+ shift = genradix_depth_shift(level);

- if (iter->offset >> genradix_depth_shift(level))
+ if (iter->offset >> shift)
return NULL;

- while (level) {
- level--;
+ while (shift > GENRADIX_ARY_SHIFT) {
+ shift -= GENRADIX_ARY_SHIFT;

- i = (iter->offset >> genradix_depth_shift(level)) &
- (GENRADIX_ARY - 1);
+ i = (iter->offset >> shift) % GENRADIX_ARY;

while (!n->children[i]) {
i++;
iter->offset = round_down(iter->offset +
- genradix_depth_size(level),
- genradix_depth_size(level));
+ (1u << shift),
+ 1u << shift);
iter->pos = (iter->offset >> PAGE_SHIFT) *
objs_per_page;
if (i == GENRADIX_ARY)
--
2.25.1
-
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