The new helper is similar to radix_tree_maybe_preload(), but tries to
preload number of nodes required to insert (1 << order) continuous
naturally-aligned elements.
This is required to push huge pages into pagecache.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
include/linux/radix-tree.h | 1 +
lib/radix-tree.c | 84 +++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 80 insertions(+), 5 deletions(-)
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index cb4b7e8cee81..084965cf90fc 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -291,6 +291,7 @@ unsigned int radix_tree_gang_lookup_slot(struct radix_tree_root *root,
unsigned long first_index, unsigned int max_items);
int radix_tree_preload(gfp_t gfp_mask);
int radix_tree_maybe_preload(gfp_t gfp_mask);
+int radix_tree_maybe_preload_order(gfp_t gfp_mask, int order);
void radix_tree_init(void);
void *radix_tree_tag_set(struct radix_tree_root *root,
unsigned long index, unsigned int tag);
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 8b7d8459bb9d..61b8fb529cef 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -38,6 +38,9 @@
#include <linux/preempt.h> /* in_interrupt() */
+/* Number of nodes in fully populated tree of given height */
+static unsigned long height_to_maxnodes[RADIX_TREE_MAX_PATH + 1] __read_mostly;
+
/*
* Radix tree node cache.
*/
@@ -342,7 +345,7 @@ radix_tree_node_free(struct radix_tree_node *node)
* To make use of this facility, the radix tree must be initialised without
* __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
*/
-static int __radix_tree_preload(gfp_t gfp_mask)
+static int __radix_tree_preload(gfp_t gfp_mask, int nr)
{
struct radix_tree_preload *rtp;
struct radix_tree_node *node;
@@ -350,14 +353,14 @@ static int __radix_tree_preload(gfp_t gfp_mask)
preempt_disable();
rtp = this_cpu_ptr(&radix_tree_preloads);
- while (rtp->nr < RADIX_TREE_PRELOAD_SIZE) {
+ while (rtp->nr < nr) {
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 < RADIX_TREE_PRELOAD_SIZE) {
+ if (rtp->nr < nr) {
node->private_data = rtp->nodes;
rtp->nodes = node;
rtp->nr++;
@@ -383,7 +386,7 @@ int radix_tree_preload(gfp_t gfp_mask)
{
/* Warn on non-sensical use... */
WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
- return __radix_tree_preload(gfp_mask);
+ return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
}
EXPORT_SYMBOL(radix_tree_preload);
@@ -395,7 +398,7 @@ EXPORT_SYMBOL(radix_tree_preload);
int radix_tree_maybe_preload(gfp_t gfp_mask)
{
if (gfpflags_allow_blocking(gfp_mask))
- return __radix_tree_preload(gfp_mask);
+ return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
/* Preloading doesn't help anything with this gfp mask, skip it */
preempt_disable();
return 0;
@@ -403,6 +406,51 @@ int radix_tree_maybe_preload(gfp_t gfp_mask)
EXPORT_SYMBOL(radix_tree_maybe_preload);
/*
+ * The same as function above, but preload number of nodes required to insert
+ * (1 << order) continuous naturally-aligned elements.
+ */
+int radix_tree_maybe_preload_order(gfp_t gfp_mask, int order)
+{
+ unsigned long nr_subtrees;
+ int nr_nodes, subtree_height;
+
+ /* Preloading doesn't help anything with this gfp mask, skip it */
+ if (!gfpflags_allow_blocking(gfp_mask)) {
+ preempt_disable();
+ return 0;
+ }
+
+ /*
+ * Calculate number and height of fully populated subtrees it takes to
+ * store (1 << order) elements.
+ */
+ nr_subtrees = 1 << order;
+ for (subtree_height = 0; nr_subtrees > RADIX_TREE_MAP_SIZE;
+ subtree_height++)
+ nr_subtrees >>= RADIX_TREE_MAP_SHIFT;
+
+ /*
+ * The worst case is zero height tree with a single item at index 0 and
+ * then inserting items starting at ULONG_MAX - (1 << order).
+ *
+ * This requires RADIX_TREE_MAX_PATH nodes to build branch from root to
+ * 0-index item.
+ */
+ nr_nodes = RADIX_TREE_MAX_PATH;
+
+ /* Plus branch to fully populated subtrees. */
+ nr_nodes += RADIX_TREE_MAX_PATH - subtree_height;
+
+ /* Root node is shared. */
+ nr_nodes--;
+
+ /* Plus nodes required to build subtrees. */
+ nr_nodes += nr_subtrees * height_to_maxnodes[subtree_height];
+
+ return __radix_tree_preload(gfp_mask, nr_nodes);
+}
+
+/*
* The maximum index which can be stored in a radix tree
*/
static inline unsigned long shift_maxindex(unsigned int shift)
@@ -1571,6 +1619,31 @@ radix_tree_node_ctor(void *arg)
INIT_LIST_HEAD(&node->private_list);
}
+static __init unsigned long __maxindex(unsigned int height)
+{
+ unsigned int width = height * RADIX_TREE_MAP_SHIFT;
+ int shift = RADIX_TREE_INDEX_BITS - width;
+
+ if (shift < 0)
+ return ~0UL;
+ if (shift >= BITS_PER_LONG)
+ return 0UL;
+ return ~0UL >> shift;
+}
+
+static __init void radix_tree_init_maxnodes(void)
+{
+ unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1];
+ unsigned int i, j;
+
+ for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
+ height_to_maxindex[i] = __maxindex(i);
+ for (i = 0; i < ARRAY_SIZE(height_to_maxnodes); i++) {
+ for (j = i; j > 0; j--)
+ height_to_maxnodes[i] += height_to_maxindex[j - 1] + 1;
+ }
+}
+
static int radix_tree_callback(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
@@ -1597,5 +1670,6 @@ void __init radix_tree_init(void)
sizeof(struct radix_tree_node), 0,
SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
radix_tree_node_ctor);
+ radix_tree_init_maxnodes();
hotcpu_notifier(radix_tree_callback, 0);
}
--
2.8.1
--
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