1#ifndef __TRACING_MAP_H 2#define __TRACING_MAP_H 3 4#define TRACING_MAP_BITS_DEFAULT 11 5#define TRACING_MAP_BITS_MAX 17 6#define TRACING_MAP_BITS_MIN 7 7 8#define TRACING_MAP_KEYS_MAX 2 9#define TRACING_MAP_VALS_MAX 3 10#define TRACING_MAP_FIELDS_MAX (TRACING_MAP_KEYS_MAX + \ 11 TRACING_MAP_VALS_MAX) 12#define TRACING_MAP_SORT_KEYS_MAX 2 13 14typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b); 15 16/* 17 * This is an overview of the tracing_map data structures and how they 18 * relate to the tracing_map API. The details of the algorithms 19 * aren't discussed here - this is just a general overview of the data 20 * structures and how they interact with the API. 21 * 22 * The central data structure of the tracing_map is an initially 23 * zeroed array of struct tracing_map_entry (stored in the map field 24 * of struct tracing_map). tracing_map_entry is a very simple data 25 * structure containing only two fields: a 32-bit unsigned 'key' 26 * variable and a pointer named 'val'. This array of struct 27 * tracing_map_entry is essentially a hash table which will be 28 * modified by a single function, tracing_map_insert(), but which can 29 * be traversed and read by a user at any time (though the user does 30 * this indirectly via an array of tracing_map_sort_entry - see the 31 * explanation of that data structure in the discussion of the 32 * sorting-related data structures below). 33 * 34 * The central function of the tracing_map API is 35 * tracing_map_insert(). tracing_map_insert() hashes the 36 * arbitrarily-sized key passed into it into a 32-bit unsigned key. 37 * It then uses this key, truncated to the array size, as an index 38 * into the array of tracing_map_entries. If the value of the 'key' 39 * field of the tracing_map_entry found at that location is 0, then 40 * that entry is considered to be free and can be claimed, by 41 * replacing the 0 in the 'key' field of the tracing_map_entry with 42 * the new 32-bit hashed key. Once claimed, that tracing_map_entry's 43 * 'val' field is then used to store a unique element which will be 44 * forever associated with that 32-bit hashed key in the 45 * tracing_map_entry. 46 * 47 * That unique element now in the tracing_map_entry's 'val' field is 48 * an instance of tracing_map_elt, where 'elt' in the latter part of 49 * that variable name is short for 'element'. The purpose of a 50 * tracing_map_elt is to hold values specific to the particular 51 * 32-bit hashed key it's assocated with. Things such as the unique 52 * set of aggregated sums associated with the 32-bit hashed key, along 53 * with a copy of the full key associated with the entry, and which 54 * was used to produce the 32-bit hashed key. 55 * 56 * When tracing_map_create() is called to create the tracing map, the 57 * user specifies (indirectly via the map_bits param, the details are 58 * unimportant for this discussion) the maximum number of elements 59 * that the map can hold (stored in the max_elts field of struct 60 * tracing_map). This is the maximum possible number of 61 * tracing_map_entries in the tracing_map_entry array which can be 62 * 'claimed' as described in the above discussion, and therefore is 63 * also the maximum number of tracing_map_elts that can be associated 64 * with the tracing_map_entry array in the tracing_map. Because of 65 * the way the insertion algorithm works, the size of the allocated 66 * tracing_map_entry array is always twice the maximum number of 67 * elements (2 * max_elts). This value is stored in the map_size 68 * field of struct tracing_map. 69 * 70 * Because tracing_map_insert() needs to work from any context, 71 * including from within the memory allocation functions themselves, 72 * both the tracing_map_entry array and a pool of max_elts 73 * tracing_map_elts are pre-allocated before any call is made to 74 * tracing_map_insert(). 75 * 76 * The tracing_map_entry array is allocated as a single block by 77 * tracing_map_create(). 78 * 79 * Because the tracing_map_elts are much larger objects and can't 80 * generally be allocated together as a single large array without 81 * failure, they're allocated individually, by tracing_map_init(). 82 * 83 * The pool of tracing_map_elts are allocated by tracing_map_init() 84 * rather than by tracing_map_create() because at the time 85 * tracing_map_create() is called, there isn't enough information to 86 * create the tracing_map_elts. Specifically,the user first needs to 87 * tell the tracing_map implementation how many fields the 88 * tracing_map_elts contain, and which types of fields they are (key 89 * or sum). The user does this via the tracing_map_add_sum_field() 90 * and tracing_map_add_key_field() functions, following which the user 91 * calls tracing_map_init() to finish up the tracing map setup. The 92 * array holding the pointers which make up the pre-allocated pool of 93 * tracing_map_elts is allocated as a single block and is stored in 94 * the elts field of struct tracing_map. 95 * 96 * There is also a set of structures used for sorting that might 97 * benefit from some minimal explanation. 98 * 99 * struct tracing_map_sort_key is used to drive the sort at any given 100 * time. By 'any given time' we mean that a different 101 * tracing_map_sort_key will be used at different times depending on 102 * whether the sort currently being performed is a primary or a 103 * secondary sort. 104 * 105 * The sort key is very simple, consisting of the field index of the 106 * tracing_map_elt field to sort on (which the user saved when adding 107 * the field), and whether the sort should be done in an ascending or 108 * descending order. 109 * 110 * For the convenience of the sorting code, a tracing_map_sort_entry 111 * is created for each tracing_map_elt, again individually allocated 112 * to avoid failures that might be expected if allocated as a single 113 * large array of struct tracing_map_sort_entry. 114 * tracing_map_sort_entry instances are the objects expected by the 115 * various internal sorting functions, and are also what the user 116 * ultimately receives after calling tracing_map_sort_entries(). 117 * Because it doesn't make sense for users to access an unordered and 118 * sparsely populated tracing_map directly, the 119 * tracing_map_sort_entries() function is provided so that users can 120 * retrieve a sorted list of all existing elements. In addition to 121 * the associated tracing_map_elt 'elt' field contained within the 122 * tracing_map_sort_entry, which is the object of interest to the 123 * user, tracing_map_sort_entry objects contain a number of additional 124 * fields which are used for caching and internal purposes and can 125 * safely be ignored. 126*/ 127 128struct tracing_map_field { 129 tracing_map_cmp_fn_t cmp_fn; 130 union { 131 atomic64_t sum; 132 unsigned int offset; 133 }; 134}; 135 136struct tracing_map_elt { 137 struct tracing_map *map; 138 struct tracing_map_field *fields; 139 void *key; 140 void *private_data; 141}; 142 143struct tracing_map_entry { 144 u32 key; 145 struct tracing_map_elt *val; 146}; 147 148struct tracing_map_sort_key { 149 unsigned int field_idx; 150 bool descending; 151}; 152 153struct tracing_map_sort_entry { 154 void *key; 155 struct tracing_map_elt *elt; 156 bool elt_copied; 157 bool dup; 158}; 159 160struct tracing_map_array { 161 unsigned int entries_per_page; 162 unsigned int entry_size_shift; 163 unsigned int entry_shift; 164 unsigned int entry_mask; 165 unsigned int n_pages; 166 void **pages; 167}; 168 169#define TRACING_MAP_ARRAY_ELT(array, idx) \ 170 (array->pages[idx >> array->entry_shift] + \ 171 ((idx & array->entry_mask) << array->entry_size_shift)) 172 173#define TRACING_MAP_ENTRY(array, idx) \ 174 ((struct tracing_map_entry *)TRACING_MAP_ARRAY_ELT(array, idx)) 175 176#define TRACING_MAP_ELT(array, idx) \ 177 ((struct tracing_map_elt **)TRACING_MAP_ARRAY_ELT(array, idx)) 178 179struct tracing_map { 180 unsigned int key_size; 181 unsigned int map_bits; 182 unsigned int map_size; 183 unsigned int max_elts; 184 atomic_t next_elt; 185 struct tracing_map_array *elts; 186 struct tracing_map_array *map; 187 const struct tracing_map_ops *ops; 188 void *private_data; 189 struct tracing_map_field fields[TRACING_MAP_FIELDS_MAX]; 190 unsigned int n_fields; 191 int key_idx[TRACING_MAP_KEYS_MAX]; 192 unsigned int n_keys; 193 struct tracing_map_sort_key sort_key; 194 atomic64_t hits; 195 atomic64_t drops; 196}; 197 198/** 199 * struct tracing_map_ops - callbacks for tracing_map 200 * 201 * The methods in this structure define callback functions for various 202 * operations on a tracing_map or objects related to a tracing_map. 203 * 204 * For a detailed description of tracing_map_elt objects please see 205 * the overview of tracing_map data structures at the beginning of 206 * this file. 207 * 208 * All the methods below are optional. 209 * 210 * @elt_alloc: When a tracing_map_elt is allocated, this function, if 211 * defined, will be called and gives clients the opportunity to 212 * allocate additional data and attach it to the element 213 * (tracing_map_elt->private_data is meant for that purpose). 214 * Element allocation occurs before tracing begins, when the 215 * tracing_map_init() call is made by client code. 216 * 217 * @elt_copy: At certain points in the lifetime of an element, it may 218 * need to be copied. The copy should include a copy of the 219 * client-allocated data, which can be copied into the 'to' 220 * element from the 'from' element. 221 * 222 * @elt_free: When a tracing_map_elt is freed, this function is called 223 * and allows client-allocated per-element data to be freed. 224 * 225 * @elt_clear: This callback allows per-element client-defined data to 226 * be cleared, if applicable. 227 * 228 * @elt_init: This callback allows per-element client-defined data to 229 * be initialized when used i.e. when the element is actually 230 * claimed by tracing_map_insert() in the context of the map 231 * insertion. 232 */ 233struct tracing_map_ops { 234 int (*elt_alloc)(struct tracing_map_elt *elt); 235 void (*elt_copy)(struct tracing_map_elt *to, 236 struct tracing_map_elt *from); 237 void (*elt_free)(struct tracing_map_elt *elt); 238 void (*elt_clear)(struct tracing_map_elt *elt); 239 void (*elt_init)(struct tracing_map_elt *elt); 240}; 241 242extern struct tracing_map * 243tracing_map_create(unsigned int map_bits, 244 unsigned int key_size, 245 const struct tracing_map_ops *ops, 246 void *private_data); 247extern int tracing_map_init(struct tracing_map *map); 248 249extern int tracing_map_add_sum_field(struct tracing_map *map); 250extern int tracing_map_add_key_field(struct tracing_map *map, 251 unsigned int offset, 252 tracing_map_cmp_fn_t cmp_fn); 253 254extern void tracing_map_destroy(struct tracing_map *map); 255extern void tracing_map_clear(struct tracing_map *map); 256 257extern struct tracing_map_elt * 258tracing_map_insert(struct tracing_map *map, void *key); 259extern struct tracing_map_elt * 260tracing_map_lookup(struct tracing_map *map, void *key); 261 262extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size, 263 int field_is_signed); 264extern int tracing_map_cmp_string(void *val_a, void *val_b); 265extern int tracing_map_cmp_none(void *val_a, void *val_b); 266 267extern void tracing_map_update_sum(struct tracing_map_elt *elt, 268 unsigned int i, u64 n); 269extern u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i); 270extern void tracing_map_set_field_descr(struct tracing_map *map, 271 unsigned int i, 272 unsigned int key_offset, 273 tracing_map_cmp_fn_t cmp_fn); 274extern int 275tracing_map_sort_entries(struct tracing_map *map, 276 struct tracing_map_sort_key *sort_keys, 277 unsigned int n_sort_keys, 278 struct tracing_map_sort_entry ***sort_entries); 279 280extern void 281tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries, 282 unsigned int n_entries); 283#endif /* __TRACING_MAP_H */ 284