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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __TRACING_MAP_H
#define __TRACING_MAP_H
typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b);
* 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 assocated 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 {
tracing_map_cmp_fn_t cmp_fn;
union {
atomic64_t sum;
unsigned int offset;
struct tracing_map_elt {
struct tracing_map *map;
struct tracing_map_field *fields;
void *key;
void *private_data;
struct tracing_map_entry {
u32 key;
struct tracing_map_elt *val;
struct tracing_map_sort_key {
unsigned int field_idx;
bool descending;
struct tracing_map_sort_entry {
void *key;
struct tracing_map_elt *elt;
bool elt_copied;
bool dup;
struct tracing_map_array {
unsigned int entries_per_page;
unsigned int entry_size_shift;
unsigned int entry_shift;
unsigned int entry_mask;
unsigned int n_pages;
void **pages;
#define TRACING_MAP_ARRAY_ELT(array, idx) \
(array->pages[idx >> array->entry_shift] + \
((idx & array->entry_mask) << array->entry_size_shift))
#define TRACING_MAP_ENTRY(array, idx) \
((struct tracing_map_entry *)TRACING_MAP_ARRAY_ELT(array, idx))
#define TRACING_MAP_ELT(array, idx) \
((struct tracing_map_elt **)TRACING_MAP_ARRAY_ELT(array, idx))
struct tracing_map {
unsigned int key_size;
unsigned int map_bits;
unsigned int map_size;
unsigned int max_elts;
atomic_t next_elt;
struct tracing_map_array *elts;
struct tracing_map_array *map;
const struct tracing_map_ops *ops;
void *private_data;
struct tracing_map_field fields[TRACING_MAP_FIELDS_MAX];
unsigned int n_fields;
int key_idx[TRACING_MAP_KEYS_MAX];
unsigned int n_keys;
struct tracing_map_sort_key sort_key;
atomic64_t hits;
atomic64_t drops;
* 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_copy: At certain points in the lifetime of an element, it may
* need to be copied. The copy should include a copy of the
* client-allocated data, which can be copied into the 'to'
* element from the 'from' element.
* @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 {
int (*elt_alloc)(struct tracing_map_elt *elt);
void (*elt_copy)(struct tracing_map_elt *to,
struct tracing_map_elt *from);
void (*elt_free)(struct tracing_map_elt *elt);
void (*elt_clear)(struct tracing_map_elt *elt);
void (*elt_init)(struct tracing_map_elt *elt);
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_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 u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i);
extern void tracing_map_set_field_descr(struct tracing_map *map,
unsigned int i,
unsigned int key_offset,
tracing_map_cmp_fn_t cmp_fn);
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 */