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authorMatthew Wilcox <mawilcox@microsoft.com>2016-12-17 08:18:17 -0500
committerMatthew Wilcox <mawilcox@microsoft.com>2017-02-13 21:44:02 -0500
commitd37cacc5adace7f3e0824e1f559192ad7299d029 (patch)
tree9932ecc9ba3010ecc53bdbf5cd299eb0842106ec /lib/radix-tree.c
parent7ad3d4d85c7af9632055a6ac0aa15b6b6a321c6b (diff)
ida: Use exceptional entries for small IDAs
We can use the root entry as a bitmap and save allocating a 128 byte bitmap for an IDA that contains only a few entries (30 on a 32-bit machine, 62 on a 64-bit machine). This costs about 300 bytes of kernel text on x86-64, so as long as 3 IDAs fall into this category, this is a net win for memory consumption. Thanks to Rasmus Villemoes for his work documenting the problem and collecting statistics on IDAs. Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Diffstat (limited to 'lib/radix-tree.c')
-rw-r--r--lib/radix-tree.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 7b9f8515033e..14130ab197c0 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -338,6 +338,14 @@ static void dump_ida_node(void *entry, unsigned long index)
for (i = 0; i < RADIX_TREE_MAP_SIZE; i++)
dump_ida_node(node->slots[i],
index | (i << node->shift));
+ } else if (radix_tree_exceptional_entry(entry)) {
+ pr_debug("ida excp: %p offset %d indices %lu-%lu data %lx\n",
+ entry, (int)(index & RADIX_TREE_MAP_MASK),
+ index * IDA_BITMAP_BITS,
+ index * IDA_BITMAP_BITS + BITS_PER_LONG -
+ RADIX_TREE_EXCEPTIONAL_SHIFT,
+ (unsigned long)entry >>
+ RADIX_TREE_EXCEPTIONAL_SHIFT);
} else {
struct ida_bitmap *bitmap = entry;