// SPDX-License-Identifier: GPL-2.0 #ifndef __TRACING_MAP_H #define __TRACING_MAP_H #define TRACING_MAP_BITS_DEFAULT … #define TRACING_MAP_BITS_MAX … #define TRACING_MAP_BITS_MIN … #define TRACING_MAP_KEYS_MAX … #define TRACING_MAP_VALS_MAX … #define TRACING_MAP_FIELDS_MAX … #define TRACING_MAP_VARS_MAX … #define TRACING_MAP_SORT_KEYS_MAX … tracing_map_cmp_fn_t; /* * This is an overview of the tracing_map data structures and how they * relate to the tracing_map API. The details of the algorithms * aren't discussed here - this is just a general overview of the data * structures and how they interact with the API. * * The central data structure of the tracing_map is an initially * zeroed array of struct tracing_map_entry (stored in the map field * of struct tracing_map). tracing_map_entry is a very simple data * structure containing only two fields: a 32-bit unsigned 'key' * variable and a pointer named 'val'. This array of struct * tracing_map_entry is essentially a hash table which will be * modified by a single function, tracing_map_insert(), but which can * be traversed and read by a user at any time (though the user does * this indirectly via an array of tracing_map_sort_entry - see the * explanation of that data structure in the discussion of the * sorting-related data structures below). * * The central function of the tracing_map API is * tracing_map_insert(). tracing_map_insert() hashes the * arbitrarily-sized key passed into it into a 32-bit unsigned key. * It then uses this key, truncated to the array size, as an index * into the array of tracing_map_entries. If the value of the 'key' * field of the tracing_map_entry found at that location is 0, then * that entry is considered to be free and can be claimed, by * replacing the 0 in the 'key' field of the tracing_map_entry with * the new 32-bit hashed key. Once claimed, that tracing_map_entry's * 'val' field is then used to store a unique element which will be * forever associated with that 32-bit hashed key in the * tracing_map_entry. * * That unique element now in the tracing_map_entry's 'val' field is * an instance of tracing_map_elt, where 'elt' in the latter part of * that variable name is short for 'element'. The purpose of a * tracing_map_elt is to hold values specific to the particular * 32-bit hashed key it's associated with. Things such as the unique * set of aggregated sums associated with the 32-bit hashed key, along * with a copy of the full key associated with the entry, and which * was used to produce the 32-bit hashed key. * * When tracing_map_create() is called to create the tracing map, the * user specifies (indirectly via the map_bits param, the details are * unimportant for this discussion) the maximum number of elements * that the map can hold (stored in the max_elts field of struct * tracing_map). This is the maximum possible number of * tracing_map_entries in the tracing_map_entry array which can be * 'claimed' as described in the above discussion, and therefore is * also the maximum number of tracing_map_elts that can be associated * with the tracing_map_entry array in the tracing_map. Because of * the way the insertion algorithm works, the size of the allocated * tracing_map_entry array is always twice the maximum number of * elements (2 * max_elts). This value is stored in the map_size * field of struct tracing_map. * * Because tracing_map_insert() needs to work from any context, * including from within the memory allocation functions themselves, * both the tracing_map_entry array and a pool of max_elts * tracing_map_elts are pre-allocated before any call is made to * tracing_map_insert(). * * The tracing_map_entry array is allocated as a single block by * tracing_map_create(). * * Because the tracing_map_elts are much larger objects and can't * generally be allocated together as a single large array without * failure, they're allocated individually, by tracing_map_init(). * * The pool of tracing_map_elts are allocated by tracing_map_init() * rather than by tracing_map_create() because at the time * tracing_map_create() is called, there isn't enough information to * create the tracing_map_elts. Specifically,the user first needs to * tell the tracing_map implementation how many fields the * tracing_map_elts contain, and which types of fields they are (key * or sum). The user does this via the tracing_map_add_sum_field() * and tracing_map_add_key_field() functions, following which the user * calls tracing_map_init() to finish up the tracing map setup. The * array holding the pointers which make up the pre-allocated pool of * tracing_map_elts is allocated as a single block and is stored in * the elts field of struct tracing_map. * * There is also a set of structures used for sorting that might * benefit from some minimal explanation. * * struct tracing_map_sort_key is used to drive the sort at any given * time. By 'any given time' we mean that a different * tracing_map_sort_key will be used at different times depending on * whether the sort currently being performed is a primary or a * secondary sort. * * The sort key is very simple, consisting of the field index of the * tracing_map_elt field to sort on (which the user saved when adding * the field), and whether the sort should be done in an ascending or * descending order. * * For the convenience of the sorting code, a tracing_map_sort_entry * is created for each tracing_map_elt, again individually allocated * to avoid failures that might be expected if allocated as a single * large array of struct tracing_map_sort_entry. * tracing_map_sort_entry instances are the objects expected by the * various internal sorting functions, and are also what the user * ultimately receives after calling tracing_map_sort_entries(). * Because it doesn't make sense for users to access an unordered and * sparsely populated tracing_map directly, the * tracing_map_sort_entries() function is provided so that users can * retrieve a sorted list of all existing elements. In addition to * the associated tracing_map_elt 'elt' field contained within the * tracing_map_sort_entry, which is the object of interest to the * user, tracing_map_sort_entry objects contain a number of additional * fields which are used for caching and internal purposes and can * safely be ignored. */ struct tracing_map_field { … }; struct tracing_map_elt { … }; struct tracing_map_entry { … }; struct tracing_map_sort_key { … }; struct tracing_map_sort_entry { … }; struct tracing_map_array { … }; #define TRACING_MAP_ARRAY_ELT(array, idx) … #define TRACING_MAP_ENTRY(array, idx) … #define TRACING_MAP_ELT(array, idx) … struct tracing_map { … }; /** * struct tracing_map_ops - callbacks for tracing_map * * The methods in this structure define callback functions for various * operations on a tracing_map or objects related to a tracing_map. * * For a detailed description of tracing_map_elt objects please see * the overview of tracing_map data structures at the beginning of * this file. * * All the methods below are optional. * * @elt_alloc: When a tracing_map_elt is allocated, this function, if * defined, will be called and gives clients the opportunity to * allocate additional data and attach it to the element * (tracing_map_elt->private_data is meant for that purpose). * Element allocation occurs before tracing begins, when the * tracing_map_init() call is made by client code. * * @elt_free: When a tracing_map_elt is freed, this function is called * and allows client-allocated per-element data to be freed. * * @elt_clear: This callback allows per-element client-defined data to * be cleared, if applicable. * * @elt_init: This callback allows per-element client-defined data to * be initialized when used i.e. when the element is actually * claimed by tracing_map_insert() in the context of the map * insertion. */ struct tracing_map_ops { … }; extern struct tracing_map * tracing_map_create(unsigned int map_bits, unsigned int key_size, const struct tracing_map_ops *ops, void *private_data); extern int tracing_map_init(struct tracing_map *map); extern int tracing_map_add_sum_field(struct tracing_map *map); extern int tracing_map_add_var(struct tracing_map *map); extern int tracing_map_add_key_field(struct tracing_map *map, unsigned int offset, tracing_map_cmp_fn_t cmp_fn); extern void tracing_map_destroy(struct tracing_map *map); extern void tracing_map_clear(struct tracing_map *map); extern struct tracing_map_elt * tracing_map_insert(struct tracing_map *map, void *key); extern struct tracing_map_elt * tracing_map_lookup(struct tracing_map *map, void *key); extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size, int field_is_signed); extern int tracing_map_cmp_string(void *val_a, void *val_b); extern int tracing_map_cmp_none(void *val_a, void *val_b); extern void tracing_map_update_sum(struct tracing_map_elt *elt, unsigned int i, u64 n); extern void tracing_map_set_var(struct tracing_map_elt *elt, unsigned int i, u64 n); extern bool tracing_map_var_set(struct tracing_map_elt *elt, unsigned int i); extern u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i); extern u64 tracing_map_read_var(struct tracing_map_elt *elt, unsigned int i); extern u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i); extern int tracing_map_sort_entries(struct tracing_map *map, struct tracing_map_sort_key *sort_keys, unsigned int n_sort_keys, struct tracing_map_sort_entry ***sort_entries); extern void tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries, unsigned int n_entries); #endif /* __TRACING_MAP_H */
Codebase Browser
linux