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_VARS_MAX 16 14#define TRACING_MAP_SORT_KEYS_MAX 2 15 16typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b); 17 18/* 19 * This is an overview of the tracing_map data structures and how they 20 * relate to the tracing_map API. The details of the algorithms 21 * aren't discussed here - this is just a general overview of the data 22 * structures and how they interact with the API. 23 * 24 * The central data structure of the tracing_map is an initially 25 * zeroed array of struct tracing_map_entry (stored in the map field 26 * of struct tracing_map). tracing_map_entry is a very simple data 27 * structure containing only two fields: a 32-bit unsigned 'key' 28 * variable and a pointer named 'val'. This array of struct 29 * tracing_map_entry is essentially a hash table which will be 30 * modified by a single function, tracing_map_insert(), but which can 31 * be traversed and read by a user at any time (though the user does 32 * this indirectly via an array of tracing_map_sort_entry - see the 33 * explanation of that data structure in the discussion of the 34 * sorting-related data structures below). 35 * 36 * The central function of the tracing_map API is 37 * tracing_map_insert(). tracing_map_insert() hashes the 38 * arbitrarily-sized key passed into it into a 32-bit unsigned key. 39 * It then uses this key, truncated to the array size, as an index 40 * into the array of tracing_map_entries. If the value of the 'key' 41 * field of the tracing_map_entry found at that location is 0, then 42 * that entry is considered to be free and can be claimed, by 43 * replacing the 0 in the 'key' field of the tracing_map_entry with 44 * the new 32-bit hashed key. Once claimed, that tracing_map_entry's 45 * 'val' field is then used to store a unique element which will be 46 * forever associated with that 32-bit hashed key in the 47 * tracing_map_entry. 48 * 49 * That unique element now in the tracing_map_entry's 'val' field is 50 * an instance of tracing_map_elt, where 'elt' in the latter part of 51 * that variable name is short for 'element'. The purpose of a 52 * tracing_map_elt is to hold values specific to the particular 53 * 32-bit hashed key it's assocated with. Things such as the unique 54 * set of aggregated sums associated with the 32-bit hashed key, along 55 * with a copy of the full key associated with the entry, and which 56 * was used to produce the 32-bit hashed key. 57 * 58 * When tracing_map_create() is called to create the tracing map, the 59 * user specifies (indirectly via the map_bits param, the details are 60 * unimportant for this discussion) the maximum number of elements 61 * that the map can hold (stored in the max_elts field of struct 62 * tracing_map). This is the maximum possible number of 63 * tracing_map_entries in the tracing_map_entry array which can be 64 * 'claimed' as described in the above discussion, and therefore is 65 * also the maximum number of tracing_map_elts that can be associated 66 * with the tracing_map_entry array in the tracing_map. Because of 67 * the way the insertion algorithm works, the size of the allocated 68 * tracing_map_entry array is always twice the maximum number of 69 * elements (2 * max_elts). This value is stored in the map_size 70 * field of struct tracing_map. 71 * 72 * Because tracing_map_insert() needs to work from any context, 73 * including from within the memory allocation functions themselves, 74 * both the tracing_map_entry array and a pool of max_elts 75 * tracing_map_elts are pre-allocated before any call is made to 76 * tracing_map_insert(). 77 * 78 * The tracing_map_entry array is allocated as a single block by 79 * tracing_map_create(). 80 * 81 * Because the tracing_map_elts are much larger objects and can't 82 * generally be allocated together as a single large array without 83 * failure, they're allocated individually, by tracing_map_init(). 84 * 85 * The pool of tracing_map_elts are allocated by tracing_map_init() 86 * rather than by tracing_map_create() because at the time 87 * tracing_map_create() is called, there isn't enough information to 88 * create the tracing_map_elts. Specifically,the user first needs to 89 * tell the tracing_map implementation how many fields the 90 * tracing_map_elts contain, and which types of fields they are (key 91 * or sum). The user does this via the tracing_map_add_sum_field() 92 * and tracing_map_add_key_field() functions, following which the user 93 * calls tracing_map_init() to finish up the tracing map setup. The 94 * array holding the pointers which make up the pre-allocated pool of 95 * tracing_map_elts is allocated as a single block and is stored in 96 * the elts field of struct tracing_map. 97 * 98 * There is also a set of structures used for sorting that might 99 * benefit from some minimal explanation. 100 * 101 * struct tracing_map_sort_key is used to drive the sort at any given 102 * time. By 'any given time' we mean that a different 103 * tracing_map_sort_key will be used at different times depending on 104 * whether the sort currently being performed is a primary or a 105 * secondary sort. 106 * 107 * The sort key is very simple, consisting of the field index of the 108 * tracing_map_elt field to sort on (which the user saved when adding 109 * the field), and whether the sort should be done in an ascending or 110 * descending order. 111 * 112 * For the convenience of the sorting code, a tracing_map_sort_entry 113 * is created for each tracing_map_elt, again individually allocated 114 * to avoid failures that might be expected if allocated as a single 115 * large array of struct tracing_map_sort_entry. 116 * tracing_map_sort_entry instances are the objects expected by the 117 * various internal sorting functions, and are also what the user 118 * ultimately receives after calling tracing_map_sort_entries(). 119 * Because it doesn't make sense for users to access an unordered and 120 * sparsely populated tracing_map directly, the 121 * tracing_map_sort_entries() function is provided so that users can 122 * retrieve a sorted list of all existing elements. In addition to 123 * the associated tracing_map_elt 'elt' field contained within the 124 * tracing_map_sort_entry, which is the object of interest to the 125 * user, tracing_map_sort_entry objects contain a number of additional 126 * fields which are used for caching and internal purposes and can 127 * safely be ignored. 128*/ 129 130struct tracing_map_field { 131 tracing_map_cmp_fn_t cmp_fn; 132 union { 133 atomic64_t sum; 134 unsigned int offset; 135 }; 136}; 137 138struct tracing_map_elt { 139 struct tracing_map *map; 140 struct tracing_map_field *fields; 141 atomic64_t *vars; 142 bool *var_set; 143 void *key; 144 void *private_data; 145}; 146 147struct tracing_map_entry { 148 u32 key; 149 struct tracing_map_elt *val; 150}; 151 152struct tracing_map_sort_key { 153 unsigned int field_idx; 154 bool descending; 155}; 156 157struct tracing_map_sort_entry { 158 void *key; 159 struct tracing_map_elt *elt; 160 bool elt_copied; 161 bool dup; 162}; 163 164struct tracing_map_array { 165 unsigned int entries_per_page; 166 unsigned int entry_size_shift; 167 unsigned int entry_shift; 168 unsigned int entry_mask; 169 unsigned int n_pages; 170 void **pages; 171}; 172 173#define TRACING_MAP_ARRAY_ELT(array, idx) \ 174 (array->pages[idx >> array->entry_shift] + \ 175 ((idx & array->entry_mask) << array->entry_size_shift)) 176 177#define TRACING_MAP_ENTRY(array, idx) \ 178 ((struct tracing_map_entry *)TRACING_MAP_ARRAY_ELT(array, idx)) 179 180#define TRACING_MAP_ELT(array, idx) \ 181 ((struct tracing_map_elt **)TRACING_MAP_ARRAY_ELT(array, idx)) 182 183struct tracing_map { 184 unsigned int key_size; 185 unsigned int map_bits; 186 unsigned int map_size; 187 unsigned int max_elts; 188 atomic_t next_elt; 189 struct tracing_map_array *elts; 190 struct tracing_map_array *map; 191 const struct tracing_map_ops *ops; 192 void *private_data; 193 struct tracing_map_field fields[TRACING_MAP_FIELDS_MAX]; 194 unsigned int n_fields; 195 int key_idx[TRACING_MAP_KEYS_MAX]; 196 unsigned int n_keys; 197 struct tracing_map_sort_key sort_key; 198 unsigned int n_vars; 199 atomic64_t hits; 200 atomic64_t drops; 201}; 202 203/** 204 * struct tracing_map_ops - callbacks for tracing_map 205 * 206 * The methods in this structure define callback functions for various 207 * operations on a tracing_map or objects related to a tracing_map. 208 * 209 * For a detailed description of tracing_map_elt objects please see 210 * the overview of tracing_map data structures at the beginning of 211 * this file. 212 * 213 * All the methods below are optional. 214 * 215 * @elt_alloc: When a tracing_map_elt is allocated, this function, if 216 * defined, will be called and gives clients the opportunity to 217 * allocate additional data and attach it to the element 218 * (tracing_map_elt->private_data is meant for that purpose). 219 * Element allocation occurs before tracing begins, when the 220 * tracing_map_init() call is made by client code. 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_free)(struct tracing_map_elt *elt); 236 void (*elt_clear)(struct tracing_map_elt *elt); 237 void (*elt_init)(struct tracing_map_elt *elt); 238}; 239 240extern struct tracing_map * 241tracing_map_create(unsigned int map_bits, 242 unsigned int key_size, 243 const struct tracing_map_ops *ops, 244 void *private_data); 245extern int tracing_map_init(struct tracing_map *map); 246 247extern int tracing_map_add_sum_field(struct tracing_map *map); 248extern int tracing_map_add_var(struct tracing_map *map); 249extern int tracing_map_add_key_field(struct tracing_map *map, 250 unsigned int offset, 251 tracing_map_cmp_fn_t cmp_fn); 252 253extern void tracing_map_destroy(struct tracing_map *map); 254extern void tracing_map_clear(struct tracing_map *map); 255 256extern struct tracing_map_elt * 257tracing_map_insert(struct tracing_map *map, void *key); 258extern struct tracing_map_elt * 259tracing_map_lookup(struct tracing_map *map, void *key); 260 261extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size, 262 int field_is_signed); 263extern int tracing_map_cmp_string(void *val_a, void *val_b); 264extern int tracing_map_cmp_none(void *val_a, void *val_b); 265 266extern void tracing_map_update_sum(struct tracing_map_elt *elt, 267 unsigned int i, u64 n); 268extern void tracing_map_set_var(struct tracing_map_elt *elt, 269 unsigned int i, u64 n); 270extern bool tracing_map_var_set(struct tracing_map_elt *elt, unsigned int i); 271extern u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i); 272extern u64 tracing_map_read_var(struct tracing_map_elt *elt, unsigned int i); 273extern u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i); 274 275extern void tracing_map_set_field_descr(struct tracing_map *map, 276 unsigned int i, 277 unsigned int key_offset, 278 tracing_map_cmp_fn_t cmp_fn); 279extern int 280tracing_map_sort_entries(struct tracing_map *map, 281 struct tracing_map_sort_key *sort_keys, 282 unsigned int n_sort_keys, 283 struct tracing_map_sort_entry ***sort_entries); 284 285extern void 286tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries, 287 unsigned int n_entries); 288#endif /* __TRACING_MAP_H */ 289