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