#ifndef CEPH_CRUSH_CRUSH_H #define CEPH_CRUSH_CRUSH_H #include /* * 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