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Commit 9d2a8da0 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
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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: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9cf79d11

lib/radix-tree.c

+17 −11
Original line number Diff line number Diff line
@@ -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--;

		}

		/*
@@ -257,18 +259,21 @@ 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:

	return ret;
@@ -1463,14 +1468,15 @@ 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;

			node = rtp->nodes;

			rtp->nodes = node->private_data;

			kmem_cache_free(radix_tree_node_cachep, node);

			rtp->nr--;

               }

       }