radix-tree: replace preallocated node array with linked list
Currently we use per-cpu array to hold pointers to preallocated nodes.
Let's replace it with linked list. On x86_64 it saves 256 bytes in
per-cpu ELF section which may translate into freeing up 2MB of memory for
NR_CPUS==8192.
[akpm@linux-foundation.org: fix comment, coding style]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 061550d..f9ebe1c 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -65,7 +65,8 @@
*/
struct radix_tree_preload {
int nr;
- struct radix_tree_node *nodes[RADIX_TREE_PRELOAD_SIZE];
+ /* nodes->private_data points to next preallocated node */
+ struct radix_tree_node *nodes;
};
static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
@@ -197,8 +198,9 @@
*/
rtp = this_cpu_ptr(&radix_tree_preloads);
if (rtp->nr) {
- ret = rtp->nodes[rtp->nr - 1];
- rtp->nodes[rtp->nr - 1] = NULL;
+ ret = rtp->nodes;
+ rtp->nodes = ret->private_data;
+ ret->private_data = NULL;
rtp->nr--;
}
/*
@@ -257,17 +259,20 @@
preempt_disable();
rtp = this_cpu_ptr(&radix_tree_preloads);
- while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
+ while (rtp->nr < RADIX_TREE_PRELOAD_SIZE) {
preempt_enable();
node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
if (node == NULL)
goto out;
preempt_disable();
rtp = this_cpu_ptr(&radix_tree_preloads);
- if (rtp->nr < ARRAY_SIZE(rtp->nodes))
- rtp->nodes[rtp->nr++] = node;
- else
+ if (rtp->nr < RADIX_TREE_PRELOAD_SIZE) {
+ node->private_data = rtp->nodes;
+ rtp->nodes = node;
+ rtp->nr++;
+ } else {
kmem_cache_free(radix_tree_node_cachep, node);
+ }
}
ret = 0;
out:
@@ -1463,15 +1468,16 @@
{
int cpu = (long)hcpu;
struct radix_tree_preload *rtp;
+ struct radix_tree_node *node;
/* Free per-cpu pool of perloaded nodes */
if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
rtp = &per_cpu(radix_tree_preloads, cpu);
while (rtp->nr) {
- kmem_cache_free(radix_tree_node_cachep,
- rtp->nodes[rtp->nr-1]);
- rtp->nodes[rtp->nr-1] = NULL;
- rtp->nr--;
+ node = rtp->nodes;
+ rtp->nodes = node->private_data;
+ kmem_cache_free(radix_tree_node_cachep, node);
+ rtp->nr--;
}
}
return NOTIFY_OK;