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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2015-06-25 15:02:19 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-06-25 17:00:40 -0700
commit9d2a8da006fcbf2dea663c095f0a0088dfbbec15 (patch)
tree822753e767183c408f675b3f274a0c6601102727 /lib/radix-tree.c
parent9cf79d115f0d161b63161650f14ff903e4c57937 (diff)
downloadlwn-9d2a8da006fcbf2dea663c095f0a0088dfbbec15.tar.gz
lwn-9d2a8da006fcbf2dea663c095f0a0088dfbbec15.zip
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>
Diffstat (limited to 'lib/radix-tree.c')
-rw-r--r--lib/radix-tree.c28
1 files changed, 17 insertions, 11 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 061550de77bc..f9ebe1c82060 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -65,7 +65,8 @@ static struct kmem_cache *radix_tree_node_cachep;
*/
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 @@ radix_tree_node_alloc(struct radix_tree_root *root)
*/
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 @@ static int __radix_tree_preload(gfp_t gfp_mask)
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 @@ static int radix_tree_callback(struct notifier_block *nfb,
{
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;