1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __TRACING_MAP_H 3 #define __TRACING_MAP_H 4 5 #define TRACING_MAP_BITS_DEFAULT 11 6 #define TRACING_MAP_BITS_MAX 17 7 #define TRACING_MAP_BITS_MIN 7 8 9 #define TRACING_MAP_KEYS_MAX 3 10 #define TRACING_MAP_VALS_MAX 3 11 #define TRACING_MAP_FIELDS_MAX (TRACING_MAP_KEYS_MAX + \ 12 TRACING_MAP_VALS_MAX) 13 #define TRACING_MAP_SORT_KEYS_MAX 2 14 15 typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b); 16 17 /* 18 * This is an overview of the tracing_map data structures and how they 19 * relate to the tracing_map API. The details of the algorithms 20 * aren't discussed here - this is just a general overview of the data 21 * structures and how they interact with the API. 22 * 23 * The central data structure of the tracing_map is an initially 24 * zeroed array of struct tracing_map_entry (stored in the map field 25 * of struct tracing_map). tracing_map_entry is a very simple data 26 * structure containing only two fields: a 32-bit unsigned 'key' 27 * variable and a pointer named 'val'. This array of struct 28 * tracing_map_entry is essentially a hash table which will be 29 * modified by a single function, tracing_map_insert(), but which can 30 * be traversed and read by a user at any time (though the user does 31 * this indirectly via an array of tracing_map_sort_entry - see the 32 * explanation of that data structure in the discussion of the 33 * sorting-related data structures below). 34 * 35 * The central function of the tracing_map API is 36 * tracing_map_insert(). tracing_map_insert() hashes the 37 * arbitrarily-sized key passed into it into a 32-bit unsigned key. 38 * It then uses this key, truncated to the array size, as an index 39 * into the array of tracing_map_entries. If the value of the 'key' 40 * field of the tracing_map_entry found at that location is 0, then 41 * that entry is considered to be free and can be claimed, by 42 * replacing the 0 in the 'key' field of the tracing_map_entry with 43 * the new 32-bit hashed key. Once claimed, that tracing_map_entry's 44 * 'val' field is then used to store a unique element which will be 45 * forever associated with that 32-bit hashed key in the 46 * tracing_map_entry. 47 * 48 * That unique element now in the tracing_map_entry's 'val' field is 49 * an instance of tracing_map_elt, where 'elt' in the latter part of 50 * that variable name is short for 'element'. The purpose of a 51 * tracing_map_elt is to hold values specific to the particular 52 * 32-bit hashed key it's assocated with. Things such as the unique 53 * set of aggregated sums associated with the 32-bit hashed key, along 54 * with a copy of the full key associated with the entry, and which 55 * was used to produce the 32-bit hashed key. 56 * 57 * When tracing_map_create() is called to create the tracing map, the 58 * user specifies (indirectly via the map_bits param, the details are 59 * unimportant for this discussion) the maximum number of elements 60 * that the map can hold (stored in the max_elts field of struct 61 * tracing_map). This is the maximum possible number of 62 * tracing_map_entries in the tracing_map_entry array which can be 63 * 'claimed' as described in the above discussion, and therefore is 64 * also the maximum number of tracing_map_elts that can be associated 65 * with the tracing_map_entry array in the tracing_map. Because of 66 * the way the insertion algorithm works, the size of the allocated 67 * tracing_map_entry array is always twice the maximum number of 68 * elements (2 * max_elts). This value is stored in the map_size 69 * field of struct tracing_map. 70 * 71 * Because tracing_map_insert() needs to work from any context, 72 * including from within the memory allocation functions themselves, 73 * both the tracing_map_entry array and a pool of max_elts 74 * tracing_map_elts are pre-allocated before any call is made to 75 * tracing_map_insert(). 76 * 77 * The tracing_map_entry array is allocated as a single block by 78 * tracing_map_create(). 79 * 80 * Because the tracing_map_elts are much larger objects and can't 81 * generally be allocated together as a single large array without 82 * failure, they're allocated individually, by tracing_map_init(). 83 * 84 * The pool of tracing_map_elts are allocated by tracing_map_init() 85 * rather than by tracing_map_create() because at the time 86 * tracing_map_create() is called, there isn't enough information to 87 * create the tracing_map_elts. Specifically,the user first needs to 88 * tell the tracing_map implementation how many fields the 89 * tracing_map_elts contain, and which types of fields they are (key 90 * or sum). The user does this via the tracing_map_add_sum_field() 91 * and tracing_map_add_key_field() functions, following which the user 92 * calls tracing_map_init() to finish up the tracing map setup. The 93 * array holding the pointers which make up the pre-allocated pool of 94 * tracing_map_elts is allocated as a single block and is stored in 95 * the elts field of struct tracing_map. 96 * 97 * There is also a set of structures used for sorting that might 98 * benefit from some minimal explanation. 99 * 100 * struct tracing_map_sort_key is used to drive the sort at any given 101 * time. By 'any given time' we mean that a different 102 * tracing_map_sort_key will be used at different times depending on 103 * whether the sort currently being performed is a primary or a 104 * secondary sort. 105 * 106 * The sort key is very simple, consisting of the field index of the 107 * tracing_map_elt field to sort on (which the user saved when adding 108 * the field), and whether the sort should be done in an ascending or 109 * descending order. 110 * 111 * For the convenience of the sorting code, a tracing_map_sort_entry 112 * is created for each tracing_map_elt, again individually allocated 113 * to avoid failures that might be expected if allocated as a single 114 * large array of struct tracing_map_sort_entry. 115 * tracing_map_sort_entry instances are the objects expected by the 116 * various internal sorting functions, and are also what the user 117 * ultimately receives after calling tracing_map_sort_entries(). 118 * Because it doesn't make sense for users to access an unordered and 119 * sparsely populated tracing_map directly, the 120 * tracing_map_sort_entries() function is provided so that users can 121 * retrieve a sorted list of all existing elements. In addition to 122 * the associated tracing_map_elt 'elt' field contained within the 123 * tracing_map_sort_entry, which is the object of interest to the 124 * user, tracing_map_sort_entry objects contain a number of additional 125 * fields which are used for caching and internal purposes and can 126 * safely be ignored. 127 */ 128 129 struct tracing_map_field { 130 tracing_map_cmp_fn_t cmp_fn; 131 union { 132 atomic64_t sum; 133 unsigned int offset; 134 }; 135 }; 136 137 struct tracing_map_elt { 138 struct tracing_map *map; 139 struct tracing_map_field *fields; 140 void *key; 141 void *private_data; 142 }; 143 144 struct tracing_map_entry { 145 u32 key; 146 struct tracing_map_elt *val; 147 }; 148 149 struct tracing_map_sort_key { 150 unsigned int field_idx; 151 bool descending; 152 }; 153 154 struct tracing_map_sort_entry { 155 void *key; 156 struct tracing_map_elt *elt; 157 bool elt_copied; 158 bool dup; 159 }; 160 161 struct tracing_map_array { 162 unsigned int entries_per_page; 163 unsigned int entry_size_shift; 164 unsigned int entry_shift; 165 unsigned int entry_mask; 166 unsigned int n_pages; 167 void **pages; 168 }; 169 170 #define TRACING_MAP_ARRAY_ELT(array, idx) \ 171 (array->pages[idx >> array->entry_shift] + \ 172 ((idx & array->entry_mask) << array->entry_size_shift)) 173 174 #define TRACING_MAP_ENTRY(array, idx) \ 175 ((struct tracing_map_entry *)TRACING_MAP_ARRAY_ELT(array, idx)) 176 177 #define TRACING_MAP_ELT(array, idx) \ 178 ((struct tracing_map_elt **)TRACING_MAP_ARRAY_ELT(array, idx)) 179 180 struct tracing_map { 181 unsigned int key_size; 182 unsigned int map_bits; 183 unsigned int map_size; 184 unsigned int max_elts; 185 atomic_t next_elt; 186 struct tracing_map_array *elts; 187 struct tracing_map_array *map; 188 const struct tracing_map_ops *ops; 189 void *private_data; 190 struct tracing_map_field fields[TRACING_MAP_FIELDS_MAX]; 191 unsigned int n_fields; 192 int key_idx[TRACING_MAP_KEYS_MAX]; 193 unsigned int n_keys; 194 struct tracing_map_sort_key sort_key; 195 atomic64_t hits; 196 atomic64_t drops; 197 }; 198 199 /** 200 * struct tracing_map_ops - callbacks for tracing_map 201 * 202 * The methods in this structure define callback functions for various 203 * operations on a tracing_map or objects related to a tracing_map. 204 * 205 * For a detailed description of tracing_map_elt objects please see 206 * the overview of tracing_map data structures at the beginning of 207 * this file. 208 * 209 * All the methods below are optional. 210 * 211 * @elt_alloc: When a tracing_map_elt is allocated, this function, if 212 * defined, will be called and gives clients the opportunity to 213 * allocate additional data and attach it to the element 214 * (tracing_map_elt->private_data is meant for that purpose). 215 * Element allocation occurs before tracing begins, when the 216 * tracing_map_init() call is made by client code. 217 * 218 * @elt_copy: At certain points in the lifetime of an element, it may 219 * need to be copied. The copy should include a copy of the 220 * client-allocated data, which can be copied into the 'to' 221 * element from the 'from' element. 222 * 223 * @elt_free: When a tracing_map_elt is freed, this function is called 224 * and allows client-allocated per-element data to be freed. 225 * 226 * @elt_clear: This callback allows per-element client-defined data to 227 * be cleared, if applicable. 228 * 229 * @elt_init: This callback allows per-element client-defined data to 230 * be initialized when used i.e. when the element is actually 231 * claimed by tracing_map_insert() in the context of the map 232 * insertion. 233 */ 234 struct tracing_map_ops { 235 int (*elt_alloc)(struct tracing_map_elt *elt); 236 void (*elt_copy)(struct tracing_map_elt *to, 237 struct tracing_map_elt *from); 238 void (*elt_free)(struct tracing_map_elt *elt); 239 void (*elt_clear)(struct tracing_map_elt *elt); 240 void (*elt_init)(struct tracing_map_elt *elt); 241 }; 242 243 extern struct tracing_map * 244 tracing_map_create(unsigned int map_bits, 245 unsigned int key_size, 246 const struct tracing_map_ops *ops, 247 void *private_data); 248 extern int tracing_map_init(struct tracing_map *map); 249 250 extern int tracing_map_add_sum_field(struct tracing_map *map); 251 extern int tracing_map_add_key_field(struct tracing_map *map, 252 unsigned int offset, 253 tracing_map_cmp_fn_t cmp_fn); 254 255 extern void tracing_map_destroy(struct tracing_map *map); 256 extern void tracing_map_clear(struct tracing_map *map); 257 258 extern struct tracing_map_elt * 259 tracing_map_insert(struct tracing_map *map, void *key); 260 extern struct tracing_map_elt * 261 tracing_map_lookup(struct tracing_map *map, void *key); 262 263 extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size, 264 int field_is_signed); 265 extern int tracing_map_cmp_string(void *val_a, void *val_b); 266 extern int tracing_map_cmp_none(void *val_a, void *val_b); 267 268 extern void tracing_map_update_sum(struct tracing_map_elt *elt, 269 unsigned int i, u64 n); 270 extern u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i); 271 extern void tracing_map_set_field_descr(struct tracing_map *map, 272 unsigned int i, 273 unsigned int key_offset, 274 tracing_map_cmp_fn_t cmp_fn); 275 extern int 276 tracing_map_sort_entries(struct tracing_map *map, 277 struct tracing_map_sort_key *sort_keys, 278 unsigned int n_sort_keys, 279 struct tracing_map_sort_entry ***sort_entries); 280 281 extern void 282 tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries, 283 unsigned int n_entries); 284 #endif /* __TRACING_MAP_H */ 285