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 
16 typedef 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 associated 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 
130 struct tracing_map_field {
131 	tracing_map_cmp_fn_t		cmp_fn;
132 	union {
133 		atomic64_t			sum;
134 		unsigned int			offset;
135 	};
136 };
137 
138 struct 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 
147 struct tracing_map_entry {
148 	u32				key;
149 	struct tracing_map_elt		*val;
150 };
151 
152 struct tracing_map_sort_key {
153 	unsigned int			field_idx;
154 	bool				descending;
155 };
156 
157 struct tracing_map_sort_entry {
158 	void				*key;
159 	struct tracing_map_elt		*elt;
160 	bool				elt_copied;
161 	bool				dup;
162 };
163 
164 struct 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 
183 struct 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  */
233 struct 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 
240 extern struct tracing_map *
241 tracing_map_create(unsigned int map_bits,
242 		   unsigned int key_size,
243 		   const struct tracing_map_ops *ops,
244 		   void *private_data);
245 extern int tracing_map_init(struct tracing_map *map);
246 
247 extern int tracing_map_add_sum_field(struct tracing_map *map);
248 extern int tracing_map_add_var(struct tracing_map *map);
249 extern int tracing_map_add_key_field(struct tracing_map *map,
250 				     unsigned int offset,
251 				     tracing_map_cmp_fn_t cmp_fn);
252 
253 extern void tracing_map_destroy(struct tracing_map *map);
254 extern void tracing_map_clear(struct tracing_map *map);
255 
256 extern struct tracing_map_elt *
257 tracing_map_insert(struct tracing_map *map, void *key);
258 extern struct tracing_map_elt *
259 tracing_map_lookup(struct tracing_map *map, void *key);
260 
261 extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size,
262 						int field_is_signed);
263 extern int tracing_map_cmp_string(void *val_a, void *val_b);
264 extern int tracing_map_cmp_none(void *val_a, void *val_b);
265 
266 extern void tracing_map_update_sum(struct tracing_map_elt *elt,
267 				   unsigned int i, u64 n);
268 extern void tracing_map_set_var(struct tracing_map_elt *elt,
269 				unsigned int i, u64 n);
270 extern bool tracing_map_var_set(struct tracing_map_elt *elt, unsigned int i);
271 extern u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i);
272 extern u64 tracing_map_read_var(struct tracing_map_elt *elt, unsigned int i);
273 extern u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i);
274 
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