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authorMichel Lespinasse <walken@google.com>2012-10-08 19:31:30 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-09 03:22:40 -0400
commit147e615f83c2c36caf89e7a3bf78090ade6f266c (patch)
tree0cd64fd67f4b55bbe364217911a8100827c8b04f
parent85d3a316c714197f94e75c1e5b2d37607d66e5de (diff)
prio_tree: remove
After both prio_tree users have been converted to use red-black trees, there is no need to keep around the prio tree library anymore. Signed-off-by: Michel Lespinasse <walken@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Hillf Danton <dhillf@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Woodhouse <dwmw2@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat
-rw-r--r--Documentation/00-INDEX2
-rw-r--r--Documentation/prio_tree.txt107
-rw-r--r--include/linux/prio_tree.h120
-rw-r--r--init/main.c2
-rw-r--r--lib/Kconfig.debug6
-rw-r--r--lib/Makefile3
-rw-r--r--lib/prio_tree.c455
-rw-r--r--lib/prio_tree_test.c106
8 files changed, 1 insertions, 800 deletions
diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX
index 49c051380daf..f54273e2ac97 100644
--- a/Documentation/00-INDEX
+++ b/Documentation/00-INDEX
@@ -270,8 +270,6 @@ preempt-locking.txt
270 - info on locking under a preemptive kernel. 270 - info on locking under a preemptive kernel.
271printk-formats.txt 271printk-formats.txt
272 - how to get printk format specifiers right 272 - how to get printk format specifiers right
273prio_tree.txt
274 - info on radix-priority-search-tree use for indexing vmas.
275ramoops.txt 273ramoops.txt
276 - documentation of the ramoops oops/panic logging module. 274 - documentation of the ramoops oops/panic logging module.
277rbtree.txt 275rbtree.txt
diff --git a/Documentation/prio_tree.txt b/Documentation/prio_tree.txt
deleted file mode 100644
index 3aa68f9a117b..000000000000
--- a/Documentation/prio_tree.txt
+++ /dev/null
@@ -1,107 +0,0 @@
1The prio_tree.c code indexes vmas using 3 different indexes:
2 * heap_index = vm_pgoff + vm_size_in_pages : end_vm_pgoff
3 * radix_index = vm_pgoff : start_vm_pgoff
4 * size_index = vm_size_in_pages
5
6A regular radix-priority-search-tree indexes vmas using only heap_index and
7radix_index. The conditions for indexing are:
8 * ->heap_index >= ->left->heap_index &&
9 ->heap_index >= ->right->heap_index
10 * if (->heap_index == ->left->heap_index)
11 then ->radix_index < ->left->radix_index;
12 * if (->heap_index == ->right->heap_index)
13 then ->radix_index < ->right->radix_index;
14 * nodes are hashed to left or right subtree using radix_index
15 similar to a pure binary radix tree.
16
17A regular radix-priority-search-tree helps to store and query
18intervals (vmas). However, a regular radix-priority-search-tree is only
19suitable for storing vmas with different radix indices (vm_pgoff).
20
21Therefore, the prio_tree.c extends the regular radix-priority-search-tree
22to handle many vmas with the same vm_pgoff. Such vmas are handled in
232 different ways: 1) All vmas with the same radix _and_ heap indices are
24linked using vm_set.list, 2) if there are many vmas with the same radix
25index, but different heap indices and if the regular radix-priority-search
26tree cannot index them all, we build an overflow-sub-tree that indexes such
27vmas using heap and size indices instead of heap and radix indices. For
28example, in the figure below some vmas with vm_pgoff = 0 (zero) are
29indexed by regular radix-priority-search-tree whereas others are pushed
30into an overflow-subtree. Note that all vmas in an overflow-sub-tree have
31the same vm_pgoff (radix_index) and if necessary we build different
32overflow-sub-trees to handle each possible radix_index. For example,
33in figure we have 3 overflow-sub-trees corresponding to radix indices
340, 2, and 4.
35
36In the final tree the first few (prio_tree_root->index_bits) levels
37are indexed using heap and radix indices whereas the overflow-sub-trees below
38those levels (i.e. levels prio_tree_root->index_bits + 1 and higher) are
39indexed using heap and size indices. In overflow-sub-trees the size_index
40is used for hashing the nodes to appropriate places.
41
42Now, an example prio_tree:
43
44 vmas are represented [radix_index, size_index, heap_index]
45 i.e., [start_vm_pgoff, vm_size_in_pages, end_vm_pgoff]
46
47level prio_tree_root->index_bits = 3
48-----
49 _
50 0 [0,7,7] |
51 / \ |
52 ------------------ ------------ | Regular
53 / \ | radix priority
54 1 [1,6,7] [4,3,7] | search tree
55 / \ / \ |
56 ------- ----- ------ ----- | heap-and-radix
57 / \ / \ | indexed
58 2 [0,6,6] [2,5,7] [5,2,7] [6,1,7] |
59 / \ / \ / \ / \ |
60 3 [0,5,5] [1,5,6] [2,4,6] [3,4,7] [4,2,6] [5,1,6] [6,0,6] [7,0,7] |
61 / / / _
62 / / / _
63 4 [0,4,4] [2,3,5] [4,1,5] |
64 / / / |
65 5 [0,3,3] [2,2,4] [4,0,4] | Overflow-sub-trees
66 / / |
67 6 [0,2,2] [2,1,3] | heap-and-size
68 / / | indexed
69 7 [0,1,1] [2,0,2] |
70 / |
71 8 [0,0,0] |
72 _
73
74Note that we use prio_tree_root->index_bits to optimize the height
75of the heap-and-radix indexed tree. Since prio_tree_root->index_bits is
76set according to the maximum end_vm_pgoff mapped, we are sure that all
77bits (in vm_pgoff) above prio_tree_root->index_bits are 0 (zero). Therefore,
78we only use the first prio_tree_root->index_bits as radix_index.
79Whenever index_bits is increased in prio_tree_expand, we shuffle the tree
80to make sure that the first prio_tree_root->index_bits levels of the tree
81is indexed properly using heap and radix indices.
82
83We do not optimize the height of overflow-sub-trees using index_bits.
84The reason is: there can be many such overflow-sub-trees and all of
85them have to be suffled whenever the index_bits increases. This may involve
86walking the whole prio_tree in prio_tree_insert->prio_tree_expand code
87path which is not desirable. Hence, we do not optimize the height of the
88heap-and-size indexed overflow-sub-trees using prio_tree->index_bits.
89Instead the overflow sub-trees are indexed using full BITS_PER_LONG bits
90of size_index. This may lead to skewed sub-trees because most of the
91higher significant bits of the size_index are likely to be 0 (zero). In
92the example above, all 3 overflow-sub-trees are skewed. This may marginally
93affect the performance. However, processes rarely map many vmas with the
94same start_vm_pgoff but different end_vm_pgoffs. Therefore, we normally
95do not require overflow-sub-trees to index all vmas.
96
97From the above discussion it is clear that the maximum height of
98a prio_tree can be prio_tree_root->index_bits + BITS_PER_LONG.
99However, in most of the common cases we do not need overflow-sub-trees,
100so the tree height in the common cases will be prio_tree_root->index_bits.
101
102It is fair to mention here that the prio_tree_root->index_bits
103is increased on demand, however, the index_bits is not decreased when
104vmas are removed from the prio_tree. That's tricky to do. Hence, it's
105left as a home work problem.
106
107
diff --git a/include/linux/prio_tree.h b/include/linux/prio_tree.h
deleted file mode 100644
index db04abb557e0..000000000000
--- a/include/linux/prio_tree.h
+++ /dev/null
@@ -1,120 +0,0 @@
1#ifndef _LINUX_PRIO_TREE_H
2#define _LINUX_PRIO_TREE_H
3
4/*
5 * K&R 2nd ed. A8.3 somewhat obliquely hints that initial sequences of struct
6 * fields with identical types should end up at the same location. We'll use
7 * this until we can scrap struct raw_prio_tree_node.
8 *
9 * Note: all this could be done more elegantly by using unnamed union/struct
10 * fields. However, gcc 2.95.3 and apparently also gcc 3.0.4 don't support this
11 * language extension.
12 */
13
14struct raw_prio_tree_node {
15 struct prio_tree_node *left;
16 struct prio_tree_node *right;
17 struct prio_tree_node *parent;
18};
19
20struct prio_tree_node {
21 struct prio_tree_node *left;
22 struct prio_tree_node *right;
23 struct prio_tree_node *parent;
24 unsigned long start;
25 unsigned long last; /* last location _in_ interval */
26};
27
28struct prio_tree_root {
29 struct prio_tree_node *prio_tree_node;
30 unsigned short index_bits;
31 unsigned short raw;
32 /*
33 * 0: nodes are of type struct prio_tree_node
34 * 1: nodes are of type raw_prio_tree_node
35 */
36};
37
38struct prio_tree_iter {
39 struct prio_tree_node *cur;
40 unsigned long mask;
41 unsigned long value;
42 int size_level;
43
44 struct prio_tree_root *root;
45 pgoff_t r_index;
46 pgoff_t h_index;
47};
48
49static inline void prio_tree_iter_init(struct prio_tree_iter *iter,
50 struct prio_tree_root *root, pgoff_t r_index, pgoff_t h_index)
51{