180 lines
4.9 KiB
C
180 lines
4.9 KiB
C
#ifndef CEPH_CRUSH_CRUSH_H
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#define CEPH_CRUSH_CRUSH_H
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#include <linux/types.h>
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/*
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* CRUSH is a pseudo-random data distribution algorithm that
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* efficiently distributes input values (typically, data objects)
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* across a heterogeneous, structured storage cluster.
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*
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* The algorithm was originally described in detail in this paper
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* (although the algorithm has evolved somewhat since then):
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*
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* http://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf
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*
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* LGPL2
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*/
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#define CRUSH_MAGIC 0x00010000ul /* for detecting algorithm revisions */
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#define CRUSH_MAX_DEPTH 10 /* max crush hierarchy depth */
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#define CRUSH_MAX_SET 10 /* max size of a mapping result */
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/*
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* CRUSH uses user-defined "rules" to describe how inputs should be
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* mapped to devices. A rule consists of sequence of steps to perform
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* to generate the set of output devices.
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*/
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struct crush_rule_step {
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__u32 op;
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__s32 arg1;
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__s32 arg2;
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};
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/* step op codes */
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enum {
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CRUSH_RULE_NOOP = 0,
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CRUSH_RULE_TAKE = 1, /* arg1 = value to start with */
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CRUSH_RULE_CHOOSE_FIRSTN = 2, /* arg1 = num items to pick */
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/* arg2 = type */
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CRUSH_RULE_CHOOSE_INDEP = 3, /* same */
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CRUSH_RULE_EMIT = 4, /* no args */
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CRUSH_RULE_CHOOSE_LEAF_FIRSTN = 6,
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CRUSH_RULE_CHOOSE_LEAF_INDEP = 7,
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};
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/*
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* for specifying choose num (arg1) relative to the max parameter
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* passed to do_rule
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*/
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#define CRUSH_CHOOSE_N 0
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#define CRUSH_CHOOSE_N_MINUS(x) (-(x))
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/*
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* The rule mask is used to describe what the rule is intended for.
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* Given a ruleset and size of output set, we search through the
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* rule list for a matching rule_mask.
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*/
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struct crush_rule_mask {
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__u8 ruleset;
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__u8 type;
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__u8 min_size;
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__u8 max_size;
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};
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struct crush_rule {
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__u32 len;
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struct crush_rule_mask mask;
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struct crush_rule_step steps[0];
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};
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#define crush_rule_size(len) (sizeof(struct crush_rule) + \
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(len)*sizeof(struct crush_rule_step))
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/*
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* A bucket is a named container of other items (either devices or
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* other buckets). Items within a bucket are chosen using one of a
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* few different algorithms. The table summarizes how the speed of
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* each option measures up against mapping stability when items are
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* added or removed.
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*
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* Bucket Alg Speed Additions Removals
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* ------------------------------------------------
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* uniform O(1) poor poor
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* list O(n) optimal poor
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* tree O(log n) good good
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* straw O(n) optimal optimal
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*/
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enum {
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CRUSH_BUCKET_UNIFORM = 1,
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CRUSH_BUCKET_LIST = 2,
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CRUSH_BUCKET_TREE = 3,
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CRUSH_BUCKET_STRAW = 4
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};
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extern const char *crush_bucket_alg_name(int alg);
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struct crush_bucket {
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__s32 id; /* this'll be negative */
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__u16 type; /* non-zero; type=0 is reserved for devices */
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__u8 alg; /* one of CRUSH_BUCKET_* */
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__u8 hash; /* which hash function to use, CRUSH_HASH_* */
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__u32 weight; /* 16-bit fixed point */
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__u32 size; /* num items */
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__s32 *items;
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/*
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* cached random permutation: used for uniform bucket and for
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* the linear search fallback for the other bucket types.
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*/
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__u32 perm_x; /* @x for which *perm is defined */
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__u32 perm_n; /* num elements of *perm that are permuted/defined */
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__u32 *perm;
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};
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struct crush_bucket_uniform {
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struct crush_bucket h;
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__u32 item_weight; /* 16-bit fixed point; all items equally weighted */
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};
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struct crush_bucket_list {
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struct crush_bucket h;
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__u32 *item_weights; /* 16-bit fixed point */
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__u32 *sum_weights; /* 16-bit fixed point. element i is sum
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of weights 0..i, inclusive */
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};
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struct crush_bucket_tree {
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struct crush_bucket h; /* note: h.size is _tree_ size, not number of
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actual items */
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__u8 num_nodes;
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__u32 *node_weights;
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};
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struct crush_bucket_straw {
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struct crush_bucket h;
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__u32 *item_weights; /* 16-bit fixed point */
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__u32 *straws; /* 16-bit fixed point */
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};
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/*
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* CRUSH map includes all buckets, rules, etc.
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*/
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struct crush_map {
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struct crush_bucket **buckets;
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struct crush_rule **rules;
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/*
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* Parent pointers to identify the parent bucket a device or
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* bucket in the hierarchy. If an item appears more than
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* once, this is the _last_ time it appeared (where buckets
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* are processed in bucket id order, from -1 on down to
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* -max_buckets.
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*/
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__u32 *bucket_parents;
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__u32 *device_parents;
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__s32 max_buckets;
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__u32 max_rules;
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__s32 max_devices;
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};
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/* crush.c */
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extern int crush_get_bucket_item_weight(struct crush_bucket *b, int pos);
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extern void crush_calc_parents(struct crush_map *map);
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extern void crush_destroy_bucket_uniform(struct crush_bucket_uniform *b);
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extern void crush_destroy_bucket_list(struct crush_bucket_list *b);
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extern void crush_destroy_bucket_tree(struct crush_bucket_tree *b);
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extern void crush_destroy_bucket_straw(struct crush_bucket_straw *b);
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extern void crush_destroy_bucket(struct crush_bucket *b);
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extern void crush_destroy(struct crush_map *map);
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#endif
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