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
|
#ifndef CEPH_CRUSH_CRUSH_H
#define CEPH_CRUSH_CRUSH_H
#include <linux/types.h>
/*
* CRUSH is a pseudo-random data distribution algorithm that
* efficiently distributes input values (typically, data objects)
* across a heterogeneous, structured storage cluster.
*
* The algorithm was originally described in detail in this paper
* (although the algorithm has evolved somewhat since then):
*
* http://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf
*
* LGPL2
*/
#define CRUSH_MAGIC 0x00010000ul /* for detecting algorithm revisions */
#define CRUSH_MAX_DEPTH 10 /* max crush hierarchy depth */
#define CRUSH_ITEM_UNDEF 0x7ffffffe /* undefined result (internal use only) */
#define CRUSH_ITEM_NONE 0x7fffffff /* no result */
/*
* CRUSH uses user-defined "rules" to describe how inputs should be
* mapped to devices. A rule consists of sequence of steps to perform
* to generate the set of output devices.
*/
struct crush_rule_step {
__u32 op;
__s32 arg1;
__s32 arg2;
};
/* step op codes */
enum {
CRUSH_RULE_NOOP = 0,
CRUSH_RULE_TAKE = 1, /* arg1 = value to start with */
CRUSH_RULE_CHOOSE_FIRSTN = 2, /* arg1 = num items to pick */
/* arg2 = type */
CRUSH_RULE_CHOOSE_INDEP = 3, /* same */
CRUSH_RULE_EMIT = 4, /* no args */
CRUSH_RULE_CHOOSELEAF_FIRSTN = 6,
CRUSH_RULE_CHOOSELEAF_INDEP = 7,
CRUSH_RULE_SET_CHOOSE_TRIES = 8, /* override choose_total_tries */
CRUSH_RULE_SET_CHOOSELEAF_TRIES = 9, /* override chooseleaf_descend_once */
CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES = 10,
CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES = 11,
};
/*
* for specifying choose num (arg1) relative to the max parameter
* passed to do_rule
*/
#define CRUSH_CHOOSE_N 0
#define CRUSH_CHOOSE_N_MINUS(x) (-(x))
/*
* The rule mask is used to describe what the rule is intended for.
* Given a ruleset and size of output set, we search through the
* rule list for a matching rule_mask.
*/
struct crush_rule_mask {
__u8 ruleset;
__u8 type;
__u8 min_size;
__u8 max_size;
};
struct crush_rule {
__u32 len;
struct crush_rule_mask mask;
struct crush_rule_step steps[0];
};
#define crush_rule_size(len) (sizeof(struct crush_rule) + \
(len)*sizeof(struct crush_rule_step))
/*
* A bucket is a named container of other items (either devices or
* other buckets). Items within a bucket are chosen using one of a
* few different algorithms. The table summarizes how the speed of
* each option measures up against mapping stability when items are
* added or removed.
*
* Bucket Alg Speed Additions Removals
* ------------------------------------------------
* uniform O(1) poor poor
* list O(n) optimal poor
* tree O(log n) good good
* straw O(n) optimal optimal
*/
enum {
CRUSH_BUCKET_UNIFORM = 1,
CRUSH_BUCKET_LIST = 2,
CRUSH_BUCKET_TREE = 3,
CRUSH_BUCKET_STRAW = 4
};
extern const char *crush_bucket_alg_name(int alg);
struct crush_bucket {
__s32 id; /* this'll be negative */
__u16 type; /* non-zero; type=0 is reserved for devices */
__u8 alg; /* one of CRUSH_BUCKET_* */
__u8 hash; /* which hash function to use, CRUSH_HASH_* */
__u32 weight; /* 16-bit fixed point */
__u32 size; /* num items */
__s32 *items;
/*
* cached random permutation: used for uniform bucket and for
* the linear search fallback for the other bucket types.
*/
__u32 perm_x; /* @x for which *perm is defined */
__u32 perm_n; /* num elements of *perm that are permuted/defined */
__u32 *perm;
};
struct crush_bucket_uniform {
struct crush_bucket h;
__u32 item_weight; /* 16-bit fixed point; all items equally weighted */
};
struct crush_bucket_list {
struct crush_bucket h;
__u32 *item_weights; /* 16-bit fixed point */
__u32 *sum_weights; /* 16-bit fixed point. element i is sum
of weights 0..i, inclusive */
};
struct crush_bucket_tree {
struct crush_bucket h; /* note: h.size is _tree_ size, not number of
actual items */
__u8 num_nodes;
__u32 *node_weights;
};
struct crush_bucket_straw {
struct crush_bucket h;
__u32 *item_weights; /* 16-bit fixed point */
__u32 *straws; /* 16-bit fixed point */
};
/*
* CRUSH map includes all buckets, rules, etc.
*/
struct crush_map {
struct crush_bucket **buckets;
struct crush_rule **rules;
__s32 max_buckets;
__u32 max_rules;
__s32 max_devices;
/* choose local retries before re-descent */
__u32 choose_local_tries;
/* choose local attempts using a fallback permutation before
* re-descent */
__u32 choose_local_fallback_tries;
/* choose attempts before giving up */
__u32 choose_total_tries;
/* attempt chooseleaf inner descent once for firstn mode; on
* reject retry outer descent. Note that this does *not*
* apply to a collision: in that case we will retry as we used
* to. */
__u32 chooseleaf_descend_once;
/* if non-zero, feed r into chooseleaf, bit-shifted right by (r-1)
* bits. a value of 1 is best for new clusters. for legacy clusters
* that want to limit reshuffling, a value of 3 or 4 will make the
* mappings line up a bit better with previous mappings. */
__u8 chooseleaf_vary_r;
};
/* crush.c */
extern int crush_get_bucket_item_weight(const struct crush_bucket *b, int pos);
extern void crush_destroy_bucket_uniform(struct crush_bucket_uniform *b);
extern void crush_destroy_bucket_list(struct crush_bucket_list *b);
extern void crush_destroy_bucket_tree(struct crush_bucket_tree *b);
extern void crush_destroy_bucket_straw(struct crush_bucket_straw *b);
extern void crush_destroy_bucket(struct crush_bucket *b);
extern void crush_destroy_rule(struct crush_rule *r);
extern void crush_destroy(struct crush_map *map);
static inline int crush_calc_tree_node(int i)
{
return ((i+1) << 1)-1;
}
#endif
|
