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| author | Matthew Wilcox <mawilcox@microsoft.com> | 2016-12-17 14:18:17 +0100 |
|---|---|---|
| committer | Matthew Wilcox <mawilcox@microsoft.com> | 2017-02-14 03:44:02 +0100 |
| commit | d37cacc5adace7f3e0824e1f559192ad7299d029 (patch) | |
| tree | 9932ecc9ba3010ecc53bdbf5cd299eb0842106ec /lib/radix-tree.c | |
| parent | ida: Move ida_bitmap to a percpu variable (diff) | |
| download | linux-d37cacc5adace7f3e0824e1f559192ad7299d029.tar.xz linux-d37cacc5adace7f3e0824e1f559192ad7299d029.zip | |
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.c | 8 |
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; |