1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
|
/* Copyright 2016 IBM Corp.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "buddy.h"
#define BUDDY_DEBUG
#undef BUDDY_VERBOSE
#ifdef BUDDY_VERBOSE
#define BUDDY_NOISE(fmt...) printf(fmt)
#else
#define BUDDY_NOISE(fmt...) do { } while(0)
#endif
static inline unsigned int buddy_map_size(struct buddy *b)
{
return 1u << (b->max_order + 1);
}
static inline unsigned int buddy_order_start(struct buddy *b,
unsigned int order)
{
unsigned int level = b->max_order - order;
/* Starting bit of index for order */
return 1u << level;
}
static inline unsigned int buddy_index_to_node(struct buddy *b,
unsigned int index,
unsigned int order)
{
/* Ensure the index is a multiple of the order */
assert((index & ((1u << order) - 1)) == 0);
return buddy_order_start(b, order) + (index >> order);
}
static inline unsigned int buddy_node_to_index(struct buddy *b,
unsigned int node,
unsigned int order)
{
unsigned int start = buddy_order_start(b, order);
return (node - start) << order;
}
#ifdef BUDDY_DEBUG
static void buddy_check_alloc(struct buddy *b, unsigned int node)
{
assert(bitmap_tst_bit(b->map, node));
}
static void buddy_check_alloc_down(struct buddy *b, unsigned int node)
{
unsigned int i, count = 1;
while (node < buddy_map_size(b)) {
for (i = 0; i < count; i++)
buddy_check_alloc(b, node + i);
/* Down one level */
node <<= 1;
count <<= 1;
}
}
#else
static inline void buddy_check_alloc(struct buddy *b, unsigned int node) {}
static inline void buddy_check_alloc_down(struct buddy *b, unsigned int node) {}
#endif
int buddy_alloc(struct buddy *b, unsigned int order)
{
unsigned int o;
int node, index;
BUDDY_NOISE("buddy_alloc(%d)\n", order);
/*
* Find the first order up the tree from our requested order that
* has at least one free node.
*/
for (o = order; o <= b->max_order; o++) {
if (b->freecounts[o] > 0)
break;
}
/* Nothing found ? fail */
if (o > b->max_order) {
BUDDY_NOISE(" no free nodes !\n");
return -1;
}
BUDDY_NOISE(" %d free node(s) at order %d, bits %d(%d)\n",
b->freecounts[o], o,
buddy_order_start(b, o),
1u << (b->max_order - o));
/* Now find a free node */
node = bitmap_find_zero_bit(b->map, buddy_order_start(b, o),
1u << (b->max_order - o));
/* There should always be one */
assert(node >= 0);
/* Mark it allocated and decrease free count */
bitmap_set_bit(b->map, node);
b->freecounts[o]--;
/* We know that node was free which means all its children must have
* been marked "allocated". Double check.
*/
buddy_check_alloc_down(b, node);
/* We have a node, we've marked it allocated, now we need to go down
* the tree until we reach "order" which is the order we need. For
* each level along the way, we mark the buddy free and leave the
* first child allocated.
*/
while (o > order) {
/* Next level down */
o--;
node <<= 1;
BUDDY_NOISE(" order %d, using %d marking %d free\n",
o, node, node ^ 1);
bitmap_clr_bit(b->map, node ^ 1);
b->freecounts[o]++;
assert(bitmap_tst_bit(b->map, node));
}
index = buddy_node_to_index(b, node, order);
BUDDY_NOISE(" result is index %d (node %d)\n", index, node);
/* We have a node, convert it to an element number */
return index;
}
bool buddy_reserve(struct buddy *b, unsigned int index, unsigned int order)
{
unsigned int node, freenode, o;
assert(index < (1u << b->max_order));
BUDDY_NOISE("buddy_reserve(%d,%d)\n", index, order);
/* Get bit number for node */
node = buddy_index_to_node(b, index, order);
BUDDY_NOISE(" node=%d\n", node);
/* Find something free */
for (freenode = node, o = order; freenode > 0; freenode >>= 1, o++)
if (!bitmap_tst_bit(b->map, freenode))
break;
BUDDY_NOISE(" freenode=%d order %d\n", freenode, o);
/* Nothing free, error out */
if (!freenode)
return false;
/* We sit on a free node, mark it busy */
bitmap_set_bit(b->map, freenode);
assert(b->freecounts[o]);
b->freecounts[o]--;
/* We know that node was free which means all its children must have
* been marked "allocated". Double check.
*/
buddy_check_alloc_down(b, freenode);
/* Reverse-walk the path and break down nodes */
while (o > order) {
/* Next level down */
o--;
freenode <<= 1;
/* Find the right one on the path to node */
if (node & (1u << (o - order)))
freenode++;
BUDDY_NOISE(" order %d, using %d marking %d free\n",
o, freenode, freenode ^ 1);
bitmap_clr_bit(b->map, freenode ^ 1);
b->freecounts[o]++;
assert(bitmap_tst_bit(b->map, node));
}
assert(node == freenode);
return true;
}
void buddy_free(struct buddy *b, unsigned int index, unsigned int order)
{
unsigned int node;
assert(index < (1u << b->max_order));
BUDDY_NOISE("buddy_free(%d,%d)\n", index, order);
/* Get bit number for node */
node = buddy_index_to_node(b, index, order);
BUDDY_NOISE(" node=%d\n", node);
/* We assume that anything freed was fully allocated, ie,
* there is no child node of that allocation index/order
* that is already free.
*
* BUDDY_DEBUG will verify it at the cost of performances
*/
buddy_check_alloc_down(b, node);
/* Propagate if buddy is free */
while (order < b->max_order && !bitmap_tst_bit(b->map, node ^ 1)) {
BUDDY_NOISE(" order %d node %d buddy %d free, propagating\n",
order, node, node ^ 1);
/* Mark buddy busy (we are already marked busy) */
bitmap_set_bit(b->map, node ^ 1);
/* Reduce free count */
assert(b->freecounts[order] > 0);
b->freecounts[order]--;
/* Get parent */
node >>= 1;
order++;
/* It must be busy already ! */
buddy_check_alloc(b, node);
BUDDY_NOISE(" testing order %d node %d\n", order, node ^ 1);
}
/* No more coalescing, mark it free */
bitmap_clr_bit(b->map, node);
/* Increase the freelist count for that level */
b->freecounts[order]++;
BUDDY_NOISE(" free count at order %d is %d\n",
order, b->freecounts[order]);
}
void buddy_reset(struct buddy *b)
{
unsigned int bsize = BITMAP_BYTES(1u << (b->max_order + 1));
BUDDY_NOISE("buddy_reset()\n");
/* We fill the bitmap with 1's to make it completely "busy" */
memset(b->map, 0xff, bsize);
memset(b->freecounts, 0, sizeof(b->freecounts));
/* We mark the root of the tree free, this is entry 1 as entry 0
* is unused.
*/
buddy_free(b, 0, b->max_order);
}
struct buddy *buddy_create(unsigned int max_order)
{
struct buddy *b;
unsigned int bsize;
assert(max_order <= BUDDY_MAX_ORDER);
bsize = BITMAP_BYTES(1u << (max_order + 1));
b = zalloc(sizeof(struct buddy) + bsize);
b->max_order = max_order;
BUDDY_NOISE("Map @%p, size: %d bytes\n", b->map, bsize);
buddy_reset(b);
return b;
}
void buddy_destroy(struct buddy *b)
{
free(b);
}
|