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