1 #ifndef CEPH_CRUSH_CRUSH_H 2 #define CEPH_CRUSH_CRUSH_H 3 4 #ifdef __KERNEL__ 5 # include <linux/types.h> 6 #else 7 # include "crush_compat.h" 8 #endif 9 10 /* 11 * CRUSH is a pseudo-random data distribution algorithm that 12 * efficiently distributes input values (typically, data objects) 13 * across a heterogeneous, structured storage cluster. 14 * 15 * The algorithm was originally described in detail in this paper 16 * (although the algorithm has evolved somewhat since then): 17 * 18 * http://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf 19 * 20 * LGPL2 21 */ 22 23 24 #define CRUSH_MAGIC 0x00010000ul /* for detecting algorithm revisions */ 25 26 #define CRUSH_MAX_DEPTH 10 /* max crush hierarchy depth */ 27 #define CRUSH_MAX_RULESET (1<<8) /* max crush ruleset number */ 28 #define CRUSH_MAX_RULES CRUSH_MAX_RULESET /* should be the same as max rulesets */ 29 30 #define CRUSH_MAX_DEVICE_WEIGHT (100u * 0x10000u) 31 #define CRUSH_MAX_BUCKET_WEIGHT (65535u * 0x10000u) 32 33 #define CRUSH_ITEM_UNDEF 0x7ffffffe /* undefined result (internal use only) */ 34 #define CRUSH_ITEM_NONE 0x7fffffff /* no result */ 35 36 /* 37 * CRUSH uses user-defined "rules" to describe how inputs should be 38 * mapped to devices. A rule consists of sequence of steps to perform 39 * to generate the set of output devices. 40 */ 41 struct crush_rule_step { 42 __u32 op; 43 __s32 arg1; 44 __s32 arg2; 45 }; 46 47 /* step op codes */ 48 enum { 49 CRUSH_RULE_NOOP = 0, 50 CRUSH_RULE_TAKE = 1, /* arg1 = value to start with */ 51 CRUSH_RULE_CHOOSE_FIRSTN = 2, /* arg1 = num items to pick */ 52 /* arg2 = type */ 53 CRUSH_RULE_CHOOSE_INDEP = 3, /* same */ 54 CRUSH_RULE_EMIT = 4, /* no args */ 55 CRUSH_RULE_CHOOSELEAF_FIRSTN = 6, 56 CRUSH_RULE_CHOOSELEAF_INDEP = 7, 57 58 CRUSH_RULE_SET_CHOOSE_TRIES = 8, /* override choose_total_tries */ 59 CRUSH_RULE_SET_CHOOSELEAF_TRIES = 9, /* override chooseleaf_descend_once */ 60 CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES = 10, 61 CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES = 11, 62 CRUSH_RULE_SET_CHOOSELEAF_VARY_R = 12 63 }; 64 65 /* 66 * for specifying choose num (arg1) relative to the max parameter 67 * passed to do_rule 68 */ 69 #define CRUSH_CHOOSE_N 0 70 #define CRUSH_CHOOSE_N_MINUS(x) (-(x)) 71 72 /* 73 * The rule mask is used to describe what the rule is intended for. 74 * Given a ruleset and size of output set, we search through the 75 * rule list for a matching rule_mask. 76 */ 77 struct crush_rule_mask { 78 __u8 ruleset; 79 __u8 type; 80 __u8 min_size; 81 __u8 max_size; 82 }; 83 84 struct crush_rule { 85 __u32 len; 86 struct crush_rule_mask mask; 87 struct crush_rule_step steps[0]; 88 }; 89 90 #define crush_rule_size(len) (sizeof(struct crush_rule) + \ 91 (len)*sizeof(struct crush_rule_step)) 92 93 94 95 /* 96 * A bucket is a named container of other items (either devices or 97 * other buckets). Items within a bucket are chosen using one of a 98 * few different algorithms. The table summarizes how the speed of 99 * each option measures up against mapping stability when items are 100 * added or removed. 101 * 102 * Bucket Alg Speed Additions Removals 103 * ------------------------------------------------ 104 * uniform O(1) poor poor 105 * list O(n) optimal poor 106 * tree O(log n) good good 107 * straw O(n) better better 108 * straw2 O(n) optimal optimal 109 */ 110 enum { 111 CRUSH_BUCKET_UNIFORM = 1, 112 CRUSH_BUCKET_LIST = 2, 113 CRUSH_BUCKET_TREE = 3, 114 CRUSH_BUCKET_STRAW = 4, 115 CRUSH_BUCKET_STRAW2 = 5, 116 }; 117 extern const char *crush_bucket_alg_name(int alg); 118 119 /* 120 * although tree was a legacy algorithm, it has been buggy, so 121 * exclude it. 122 */ 123 #define CRUSH_LEGACY_ALLOWED_BUCKET_ALGS ( \ 124 (1 << CRUSH_BUCKET_UNIFORM) | \ 125 (1 << CRUSH_BUCKET_LIST) | \ 126 (1 << CRUSH_BUCKET_STRAW)) 127 128 struct crush_bucket { 129 __s32 id; /* this'll be negative */ 130 __u16 type; /* non-zero; type=0 is reserved for devices */ 131 __u8 alg; /* one of CRUSH_BUCKET_* */ 132 __u8 hash; /* which hash function to use, CRUSH_HASH_* */ 133 __u32 weight; /* 16-bit fixed point */ 134 __u32 size; /* num items */ 135 __s32 *items; 136 137 /* 138 * cached random permutation: used for uniform bucket and for 139 * the linear search fallback for the other bucket types. 140 */ 141 __u32 perm_x; /* @x for which *perm is defined */ 142 __u32 perm_n; /* num elements of *perm that are permuted/defined */ 143 __u32 *perm; 144 }; 145 146 struct crush_bucket_uniform { 147 struct crush_bucket h; 148 __u32 item_weight; /* 16-bit fixed point; all items equally weighted */ 149 }; 150 151 struct crush_bucket_list { 152 struct crush_bucket h; 153 __u32 *item_weights; /* 16-bit fixed point */ 154 __u32 *sum_weights; /* 16-bit fixed point. element i is sum 155 of weights 0..i, inclusive */ 156 }; 157 158 struct crush_bucket_tree { 159 struct crush_bucket h; /* note: h.size is _tree_ size, not number of 160 actual items */ 161 __u8 num_nodes; 162 __u32 *node_weights; 163 }; 164 165 struct crush_bucket_straw { 166 struct crush_bucket h; 167 __u32 *item_weights; /* 16-bit fixed point */ 168 __u32 *straws; /* 16-bit fixed point */ 169 }; 170 171 struct crush_bucket_straw2 { 172 struct crush_bucket h; 173 __u32 *item_weights; /* 16-bit fixed point */ 174 }; 175 176 177 178 /* 179 * CRUSH map includes all buckets, rules, etc. 180 */ 181 struct crush_map { 182 struct crush_bucket **buckets; 183 struct crush_rule **rules; 184 185 __s32 max_buckets; 186 __u32 max_rules; 187 __s32 max_devices; 188 189 /* choose local retries before re-descent */ 190 __u32 choose_local_tries; 191 /* choose local attempts using a fallback permutation before 192 * re-descent */ 193 __u32 choose_local_fallback_tries; 194 /* choose attempts before giving up */ 195 __u32 choose_total_tries; 196 /* attempt chooseleaf inner descent once for firstn mode; on 197 * reject retry outer descent. Note that this does *not* 198 * apply to a collision: in that case we will retry as we used 199 * to. */ 200 __u32 chooseleaf_descend_once; 201 202 /* if non-zero, feed r into chooseleaf, bit-shifted right by (r-1) 203 * bits. a value of 1 is best for new clusters. for legacy clusters 204 * that want to limit reshuffling, a value of 3 or 4 will make the 205 * mappings line up a bit better with previous mappings. */ 206 __u8 chooseleaf_vary_r; 207 208 #ifndef __KERNEL__ 209 /* 210 * version 0 (original) of straw_calc has various flaws. version 1 211 * fixes a few of them. 212 */ 213 __u8 straw_calc_version; 214 215 /* 216 * allowed bucket algs is a bitmask, here the bit positions 217 * are CRUSH_BUCKET_*. note that these are *bits* and 218 * CRUSH_BUCKET_* values are not, so we need to or together (1 219 * << CRUSH_BUCKET_WHATEVER). The 0th bit is not used to 220 * minimize confusion (bucket type values start at 1). 221 */ 222 __u32 allowed_bucket_algs; 223 224 __u32 *choose_tries; 225 #endif 226 }; 227 228 229 /* crush.c */ 230 extern int crush_get_bucket_item_weight(const struct crush_bucket *b, int pos); 231 extern void crush_destroy_bucket_uniform(struct crush_bucket_uniform *b); 232 extern void crush_destroy_bucket_list(struct crush_bucket_list *b); 233 extern void crush_destroy_bucket_tree(struct crush_bucket_tree *b); 234 extern void crush_destroy_bucket_straw(struct crush_bucket_straw *b); 235 extern void crush_destroy_bucket_straw2(struct crush_bucket_straw2 *b); 236 extern void crush_destroy_bucket(struct crush_bucket *b); 237 extern void crush_destroy_rule(struct crush_rule *r); 238 extern void crush_destroy(struct crush_map *map); 239 240 static inline int crush_calc_tree_node(int i) 241 { 242 return ((i+1) << 1)-1; 243 } 244 245 #endif 246