As far as I can tell, the only place the per-cpu ida_bitmap is populated
is in ida_pre_get. The pre-allocated element is stolen in two places in
ida_get_new_above, in both cases immediately followed by a memset(0).
Since ida_get_new_above is called with locks held, do the zeroing in
ida_pre_get, or rather let kmalloc() do it. Also, apparently gcc
generates ~44 bytes of code to do a memset(, 0, 128):
$ scripts/bloat-o-meter vmlinux.{0,1}
add/remove: 0/0 grow/shrink: 2/1 up/down: 5/-88 (-83)
Function old new delta
ida_pre_get 115 119 +4
vermagic 27 28 +1
ida_get_new_above 715 627 -88
Signed-off-by: Rasmus Villemoes <[email protected]>
---
lib/idr.c | 2 --
lib/radix-tree.c | 2 +-
2 files changed, 1 insertion(+), 3 deletions(-)
diff --git a/lib/idr.c b/lib/idr.c
index 2593ce513a18..37c552395b3a 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -300,7 +300,6 @@ int ida_get_new_above(struct ida *ida, int start, int *id)
bitmap = this_cpu_xchg(ida_bitmap, NULL);
if (!bitmap)
return -EAGAIN;
- memset(bitmap, 0, sizeof(*bitmap));
bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
rcu_assign_pointer(*slot, bitmap);
}
@@ -333,7 +332,6 @@ int ida_get_new_above(struct ida *ida, int start, int *id)
bitmap = this_cpu_xchg(ida_bitmap, NULL);
if (!bitmap)
return -EAGAIN;
- memset(bitmap, 0, sizeof(*bitmap));
__set_bit(bit, bitmap->bitmap);
radix_tree_iter_replace(root, &iter, slot, bitmap);
}
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index c8d55565fafa..553248b64d60 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -2124,7 +2124,7 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
preempt_enable();
if (!this_cpu_read(ida_bitmap)) {
- struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp);
+ struct ida_bitmap *bitmap = kzalloc(sizeof(*bitmap), gfp);
if (!bitmap)
return 0;
if (this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
--
2.15.1
