ceph/src/crush/builder.h

   1 #ifndef CEPH_CRUSH_BUILDER_H
   2 #define CEPH_CRUSH_BUILDER_H
   3
   4 #include "crush.h"
   5
   6 /** @ingroup API
   7  *
   8  * Allocate a crush_map with __malloc(3)__ and initialize it. The
   9  * caller is responsible for deallocating the crush_map with
  10  * crush_destroy().
  11  *
  12  * The content of the allocated crush_map is set with
  13  * set_optimal_crush_map(). The caller is responsible for setting each
  14  * tunable in the __crush_map__ for backward compatibility or mapping
  15  * stability.
  16  *
  17  * @returns a pointer to the newly created crush_map or NULL
  18  */
  19 extern struct crush_map *crush_create();
  20 /** @ingroup API
  21  *
  22  * Analyze the content of __map__ and set the internal values required
  23  * before it can be used to map values with crush_do_rule(). The caller
  24  * must make sure it is run before crush_do_rule() and after any
  25  * function that modifies the __map__ (crush_add_bucket(), etc.).
  26  *
  27  * @param map the crush_map
  28  */
  29 extern void crush_finalize(struct crush_map *map);
  30
  31 /* rules */
  32 /** @ingroup API
  33  *
  34  * Allocate an empty crush_rule structure large enough to store __len__ steps.
  35  * Steps can be added to a rule via crush_rule_set_step(). The __ruleset__
  36  * is a user defined integer, not used by __libcrush__ and stored in
  37  * the allocated rule at __rule->mask.ruleset__.
  38  *
  39  * The rule is designed to allow crush_do_rule() to get at least __minsize__ items
  40  * and at most __maxsize__ items.
  41  *
  42  * The __type__ is defined by the caller and will be used by
  43  * crush_find_rule() when looking for a rule and by
  44  * __CRUSH_RULE_CHOOSE*__ steps when looking for items.
  45  *
  46  * The caller is responsible for deallocating the returned pointer via
  47  * crush_destroy_rule().
  48  *
  49  * If __malloc(3)__ fails, return NULL.
  50  *
  51  * @param len number of steps in the rule
  52  * @param ruleset user defined value
  53  * @param type user defined value
  54  * @param minsize minimum number of items the rule can map
  55  * @param maxsize maximum number of items the rule can map
  56  *
  57  * @returns a pointer to the newly created rule or NULL
  58  */
  59 extern struct crush_rule *crush_make_rule(int len, int ruleset, int type, int minsize, int maxsize);
  60 /** @ingroup API
  61  *
  62  * Set the __pos__ step of the __rule__ to an operand and up to two arguments.
  63  * The value of the operand __op__ determines if the arguments are used and how:
  64  *
  65  * - __CRUSH_RULE_NOOP__ do nothing.
  66  * - __CRUSH_RULE_TAKE__ select the __arg1__ item
  67  * - __CRUSH_RULE_EMIT__ append the selection to the results and clear
  68  *     the selection
  69  *
  70  * - __CRUSH_RULE_CHOOSE_FIRSTN__ and __CRUSH_RULE_CHOOSE_INDEP__
  71  *     recursively explore each bucket currently selected, looking for
  72  *     __arg1__ items of type __arg2__ and select them.
  73  * - __CRUSH_RULE_CHOOSELEAF_FIRSTN__ and __CRUSH_RULE_CHOOSELEAF_INDEP__
  74  *     recursively explore each bucket currently selected, looking for
  75  *     __arg1__ leaves within all the buckets of type __arg2__ and
  76  *     select them.
  77  *
  78  * In all __CHOOSE__ steps, if __arg1__ is less than or equal to zero,
  79  * the number of items to select is equal to the __max_result__ argument
  80  * of crush_do_rule() minus __arg1__. It is common to set __arg1__ to zero
  81  * to select as many items as requested by __max_result__.
  82  *
  83  * - __CRUSH_RULE_SET_CHOOSE_TRIES__ and __CRUSH_RULE_SET_CHOOSELEAF_TRIES__
  84  *
  85  *   The CHOOSE_FIRSTN and CHOOSE_INDEP rule step look for buckets of
  86  *   a given type, randomly selecting them. If they are unlucky and
  87  *   find the same bucket twice, they will try N+1 times (N being the
  88  *   value of the choose_total_tries tunable). If there is a previous
  89  *   SET_CHOOSE_TRIES step in the same rule, it will try C times
  90  *   instead (C being the value of the argument of the
  91  *   SET_CHOOSE_TRIES step).
  92  *
  93  *   Note: the __choose_total_tries__ tunable defined in crush_map is
  94  *   the number of retry, not the number of tries. The number of tries
  95  *   is the number of retry+1. The SET_CHOOSE_TRIES rule step sets the
  96  *   number of tries and does not need the + 1. This confusing
  97  *   difference is inherited from an off-by-one bug from years ago.
  98  *
  99  *   The CHOOSELEAF_FIRSTN and CHOOSELEAF_INDEP rule step do the same
 100  *   as CHOOSE_FIRSTN and CHOOSE_INDEP but also recursively explore
 101  *   each bucket found, looking for a single device. The same device
 102  *   may be found in two different buckets because the crush map is
 103  *   not a strict hierarchy, it is a DAG. When such a collision
 104  *   happens, they will try again. The number of times they try to
 105  *   find a non colliding device is:
 106  *
 107  *   - If FIRSTN and there is no previous SET_CHOOSELEAF_TRIES rule
 108  *     step: try N + 1 times (N being the value of the
 109  *     __choose_total_tries__ tunable defined in crush_map)
 110  *
 111  *   - If FIRSTN and there is a previous SET_CHOOSELEAF_TRIES rule
 112  *     step: try P times (P being the value of the argument of the
 113  *     SET_CHOOSELEAF_TRIES rule step)
 114  *
 115  *   - If INDEP and there is no previous SET_CHOOSELEAF_TRIES rule
 116  *     step: try 1 time.
 117  *
 118  *   - If INDEP and there is a previous SET_CHOOSELEAF_TRIES rule step: try
 119  *     P times (P being the value of the argument of the SET_CHOOSELEAF_TRIES
 120  *     rule step)
 121  *
 122  * @param rule the rule in which the step is inserted
 123  * @param pos the zero based step index
 124  * @param op one of __CRUSH_RULE_NOOP__, __CRUSH_RULE_TAKE__, __CRUSH_RULE_CHOOSE_FIRSTN__, __CRUSH_RULE_CHOOSE_INDEP__, __CRUSH_RULE_CHOOSELEAF_FIRSTN__, __CRUSH_RULE_CHOOSELEAF_INDEP__, __CRUSH_RULE_SET_CHOOSE_TRIES__, __CRUSH_RULE_SET_CHOOSELEAF_TRIES__ or __CRUSH_RULE_EMIT__
 125  * @param arg1 first argument for __op__
 126  * @param arg2 second argument for __op__
 127  */
 128 extern void crush_rule_set_step(struct crush_rule *rule, int pos, int op, int arg1, int arg2);
 129 /** @ingroup API
 130  *
 131  * Add the __rule__ into the crush __map__ and assign it the
 132  * __ruleno__ unique identifier. If __ruleno__ is -1, the function will
 133  * assign the lowest available identifier. The __ruleno__ value must be
 134  * a positive integer lower than __CRUSH_MAX_RULES__.
 135  *
 136  * - return -ENOSPC if the rule identifier is >= __CRUSH_MAX_RULES__
 137  * - return -ENOMEM if __realloc(3)__ fails to expand the array of
 138  *   rules in the __map__
 139  *
 140  * @param map the crush_map
 141  * @param rule the rule to add to the __map__
 142  * @param ruleno a positive integer < __CRUSH_MAX_RULES__ or -1
 143  *
 144  * @returns the rule unique identifier on success, < 0 on error
 145  */
 146 extern int crush_add_rule(struct crush_map *map, struct crush_rule *rule, int ruleno);
 147
 148 /* buckets */
 149 extern int crush_get_next_bucket_id(struct crush_map *map);
 150 /** @ingroup API
 151  *
 152  * Add __bucket__ into the crush __map__ and assign it the
 153  * __bucketno__ unique identifier. If __bucketno__ is 0, the function
 154  * will assign the lowest available identifier.  The bucket identifier
 155  * must be a negative integer. The bucket identifier is returned via
 156  * __idout__.
 157  *
 158  * - return -ENOMEM if __realloc(3)__ fails to expand the array of
 159  *   buckets in the __map__
 160  * - return -EEXIST if the __bucketno__ identifier is already assigned
 161  *   to another bucket.
 162  *
 163  * @param[in] map the crush_map
 164  * @param[in] bucketno the bucket unique identifer or 0
 165  * @param[in] bucket the bucket to add to the __map__
 166  * @param[out] idout a pointer to the bucket identifier
 167  *
 168  * @returns 0 on success, < 0 on error
 169  */
 170 extern int crush_add_bucket(struct crush_map *map,
 171                             int bucketno,
 172                             struct crush_bucket *bucket, int *idout);
 173 /** @ingroup API
 174  *
 175  * Allocate a crush_bucket with __malloc(3)__ and initialize it. The
 176  * content of the bucket is filled with __size__ items from
 177  * __items__. The item selection is set to use __alg__ which is one of
 178  * ::CRUSH_BUCKET_UNIFORM , ::CRUSH_BUCKET_LIST or
 179  * ::CRUSH_BUCKET_STRAW2. The initial __items__ are assigned a
 180  * weight from the __weights__ array, depending on the value of
 181  * __alg__. If __alg__ is ::CRUSH_BUCKET_UNIFORM, all items are set
 182  * to have a weight equal to __weights[0]__, otherwise the weight of
 183  * __items[x]__ is set to be the value of __weights[x]__.
 184  *
 185  * The caller is responsible for deallocating the returned pointer via
 186  * crush_destroy_bucket().
 187  *
 188  * @param map __unused__
 189  * @param alg algorithm for item selection
 190  * @param hash always set to CRUSH_HASH_RJENKINS1
 191  * @param type user defined bucket type
 192  * @param size of the __items__ array
 193  * @param items array of __size__ items
 194  * @param weights the weight of each item in __items__, depending on __alg__
 195  *
 196  * @returns a pointer to the newly created bucket or NULL
 197  */
 198 struct crush_bucket *crush_make_bucket(struct crush_map *map, int alg, int hash, int type, int size, int *items, int *weights);
 199 extern struct crush_choose_arg *crush_make_choose_args(struct crush_map *map, int num_positions);
 200 extern void crush_destroy_choose_args(struct crush_choose_arg *args);
 201 /** @ingroup API
 202  *
 203  * Add __item__ to __bucket__ with __weight__. The weight of the new
 204  * item is added to the weight of the bucket so that it reflects
 205  * the total weight of all items.
 206  *
 207  * If __bucket->alg__ is ::CRUSH_BUCKET_UNIFORM, the value of __weight__ must be equal to
 208  * __(struct crush_bucket_uniform *)bucket->item_weight__.
 209  *
 210  * - return -ENOMEM if the __bucket__ cannot be resized with __realloc(3)__.
 211  * - return -ERANGE if adding __weight__ to the weight of the bucket overflows.
 212  * - return -EINVAL if __bucket->alg__ is ::CRUSH_BUCKET_UNIFORM and
 213  *   the __weight__ is not equal to __(struct crush_bucket_uniform *)bucket->item_weight__.
 214  * - return -1 if the value of __bucket->alg__ is unknown.
 215  *
 216  * @returns 0 on success, < 0 on error
 217  */
 218 extern int crush_bucket_add_item(struct crush_map *map, struct crush_bucket *bucket, int item, int weight);
 219 /** @ingroup API
 220  *
 221  * If __bucket->alg__ is ::CRUSH_BUCKET_UNIFORM,
 222  * __(struct crush_bucket_uniform *)bucket->item_weight__ is set to __weight__ and the
 223  * weight of the bucket is set to be the number of items in the bucket times the weight.
 224  * The return value is the difference between the new bucket weight and the former
 225  * bucket weight. The __item__ argument is ignored.
 226  *
 227  * If __bucket->alg__ is different from ::CRUSH_BUCKET_UNIFORM,
 228  * set the  __weight__ of  __item__ in __bucket__. The former weight of the
 229  * item is subtracted from the weight of the bucket and the new weight is added.
 230  * The return value is the difference between the new item weight and the former
 231  * item weight.
 232  *
 233  * @returns the difference between the new weight and the former weight
 234  */
 235 extern int crush_bucket_adjust_item_weight(struct crush_map *map, struct crush_bucket *bucket, int item, int weight);
 236 /** @ingroup API
 237  *
 238  * Recursively update the weight of __bucket__ and its children, deep
 239  * first. The __bucket__ weight is set to the sum of the weight of the
 240  * items it contains.
 241  *
 242  * - return -ERANGE if the sum of the weight of the items in __bucket__ overflows.
 243  * - return -1 if the value of __bucket->alg__ is unknown.
 244  *
 245  * @param map a crush_map containing __bucket__
 246  * @param bucket the root of the tree to reweight
 247  * @returns 0 on success, < 0 on error
 248  */
 249 extern int crush_reweight_bucket(struct crush_map *map, struct crush_bucket *bucket);
 250 /** @ingroup API
 251  *
 252  * Remove __bucket__ from __map__ and deallocate it via crush_destroy_bucket().
 253  * __assert(3)__ that __bucket__ is in __map__. The caller is responsible for
 254  * making sure the bucket is not the child of any other bucket in the __map__.
 255  *
 256  * @param map a crush_map containing __bucket__
 257  * @param bucket the bucket to remove from __map__
 258  * @returns 0
 259  */
 260 extern int crush_remove_bucket(struct crush_map *map, struct crush_bucket *bucket);
 261 /** @ingroup API
 262  *
 263  * Remove __item__ from __bucket__ and subtract the item weight from
 264  * the bucket weight. If the weight of the item is greater than the
 265  * weight of the bucket, silentely set the bucket weight to zero.
 266  *
 267  * - return -ENOMEM if the __bucket__ cannot be sized down with __realloc(3)__.
 268  * - return -1 if the value of __bucket->alg__ is unknown.
 269  *
 270  * @param map __unused__
 271  * @param bucket the bucket from which __item__ is removed
 272  * @param item the item to remove from __bucket__
 273  * @returns 0 on success, < 0 on error
 274  */
 275 extern int crush_bucket_remove_item(struct crush_map *map, struct crush_bucket *bucket, int item);
 276
 277 struct crush_bucket_uniform *
 278 crush_make_uniform_bucket(int hash, int type, int size,
 279                           int *items,
 280                           int item_weight);
 281 struct crush_bucket_list*
 282 crush_make_list_bucket(int hash, int type, int size,
 283                        int *items,
 284                        int *weights);
 285 struct crush_bucket_tree*
 286 crush_make_tree_bucket(int hash, int type, int size,
 287                        int *items,    /* in leaf order */
 288                        int *weights);
 289 struct crush_bucket_straw *
 290 crush_make_straw_bucket(struct crush_map *map,
 291                         int hash, int type, int size,
 292                         int *items,
 293                         int *weights);
 294
 295 extern int crush_addition_is_unsafe(__u32 a, __u32 b);
 296 extern int crush_multiplication_is_unsafe(__u32  a, __u32 b);
 297
 298 /** @ingroup API
 299  *
 300  * Set the __map__ tunables to implement the most ancient behavior,
 301  * for backward compatibility purposes only.
 302  *
 303  * - choose_local_tries == 2
 304  * - choose_local_fallback_tries == 5
 305  * - choose_total_tries == 19
 306  * - chooseleaf_descend_once == 0
 307  * - chooseleaf_vary_r == 0
 308  * - straw_calc_version == 0
 309  * - chooseleaf_stable = 0
 310  *
 311  * See the __crush_map__ documentation for more information about
 312  * each tunable.
 313  *
 314  * @param map a crush_map
 315  */
 316 extern void set_legacy_crush_map(struct crush_map *map);
 317 /** @ingroup API
 318  *
 319  * Set the __map__ tunables to implement the optimal behavior. These
 320  * are the values set by crush_create(). It does not guarantee a
 321  * stable mapping after an upgrade.
 322  *
 323  * For instance when a bug is fixed it may significantly change the
 324  * mapping. In that case a new tunable (say tunable_new) is added so
 325  * the caller can control when the bug fix is activated. The
 326  * set_optimal_crush_map() function will always set all tunables,
 327  * including tunable_new, to fix all bugs even if it means changing
 328  * the mapping. If the caller needs fine grained control on the
 329  * tunables to upgrade to a new version without changing the mapping,
 330  * it needs to set the __crush_map__ tunables individually.
 331  *
 332  * See the __crush_map__ documentation for more information about
 333  * each tunable.
 334  *
 335  * @param map a crush_map
 336  */
 337 extern void set_optimal_crush_map(struct crush_map *map);
 338
 339 #endif