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Diffstat (limited to 'src/crush/mapper.h')
-rw-r--r-- | src/crush/mapper.h | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/src/crush/mapper.h b/src/crush/mapper.h new file mode 100644 index 00000000..e76be767 --- /dev/null +++ b/src/crush/mapper.h @@ -0,0 +1,93 @@ +#ifndef CEPH_CRUSH_MAPPER_H +#define CEPH_CRUSH_MAPPER_H + +/* + * CRUSH functions for find rules and then mapping an input to an + * output set. + * + * LGPL2.1 + */ + +#include "crush.h" + +extern int crush_find_rule(const struct crush_map *map, int ruleset, int type, int size); +/** @ingroup API + * + * Map __x__ to __result_max__ items and store them in the __result__ + * array. The mapping is done by following each step of the rule + * __ruleno__. See crush_make_rule(), crush_rule_set_step() and + * crush_add_rule() for more information on how the rules are created, + * populated and added to the crush __map__. + * + * The return value is the the number of items in the __result__ + * array. If the caller asked for __result_max__ items and the return + * value is X where X < __result_max__, the content of __result[0,X[__ + * is defined but the content of __result[X,result_max[__ is + * undefined. For example: + * + * crush_do_rule(map, ruleno=1, x=1, result, result_max=3,...) == 1 + * result[0] is set + * result[1] is undefined + * result[2] is undefined + * + * An entry in the __result__ array is either an item in the crush + * __map__ or ::CRUSH_ITEM_NONE if no item was found. For example: + * + * crush_do_rule(map, ruleno=1, x=1, result, result_max=4,...) == 2 + * result[0] is CRUSH_ITEM_NONE + * result[1] is item number 5 + * result[2] is undefined + * result[3] is undefined + * + * The __weight__ array contains the probabilities that a leaf is + * ignored even if it is selected. It is a 16.16 fixed point + * number in the range [0x00000,0x10000]. The lower the value, the + * more often the leaf is ignored. For instance: + * + * - weight[leaf] == 0x00000 == 0.0 always ignore + * - weight[leaf] == 0x10000 == 1.0 never ignore + * - weight[leaf] == 0x08000 == 0.5 ignore 50% of the time + * - weight[leaf] == 0x04000 == 0.25 ignore 75% of the time + * - etc. + * + * During mapping, each leaf is checked against the __weight__ array, + * using the leaf as an index. If there is no entry in __weight__ for + * the leaf, it is ignored. If there is an entry, the leaf will be + * ignored some of the time, depending on the probability. + * + * The __cwin__ argument must be set as follows: + * + * char __cwin__[crush_work_size(__map__, __result_max__)]; + * crush_init_workspace(__map__, __cwin__); + * + * @param map the crush_map + * @param ruleno a positive integer < __CRUSH_MAX_RULES__ + * @param x the value to map to __result_max__ items + * @param result an array of items of size __result_max__ + * @param result_max the size of the __result__ array + * @param weights an array of weights of size __weight_max__ + * @param weight_max the size of the __weights__ array + * @param cwin must be an char array initialized by crush_init_workspace + * @param choose_args weights and ids for each known bucket + * + * @return 0 on error or the size of __result__ on success + */ +extern int crush_do_rule(const struct crush_map *map, + int ruleno, + int x, int *result, int result_max, + const __u32 *weights, int weight_max, + void *cwin, const struct crush_choose_arg *choose_args); + +/* Returns the exact amount of workspace that will need to be used + for a given combination of crush_map and result_max. The caller can + then allocate this much on its own, either on the stack, in a + per-thread long-lived buffer, or however it likes. */ + +static inline size_t crush_work_size(const struct crush_map *map, + int result_max) { + return map->working_size + result_max * 3 * sizeof(__u32); +} + +extern void crush_init_workspace(const struct crush_map *m, void *v); + +#endif |