kernel/trace/tracing_map.h

   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            2
  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_SORT_KEYS_MAX       2
  14
  15 typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b);
  16
  17 /*
  18  * This is an overview of the tracing_map data structures and how they
  19  * relate to the tracing_map API.  The details of the algorithms
  20  * aren't discussed here - this is just a general overview of the data
  21  * structures and how they interact with the API.
  22  *
  23  * The central data structure of the tracing_map is an initially
  24  * zeroed array of struct tracing_map_entry (stored in the map field
  25  * of struct tracing_map).  tracing_map_entry is a very simple data
  26  * structure containing only two fields: a 32-bit unsigned 'key'
  27  * variable and a pointer named 'val'.  This array of struct
  28  * tracing_map_entry is essentially a hash table which will be
  29  * modified by a single function, tracing_map_insert(), but which can
  30  * be traversed and read by a user at any time (though the user does
  31  * this indirectly via an array of tracing_map_sort_entry - see the
  32  * explanation of that data structure in the discussion of the
  33  * sorting-related data structures below).
  34  *
  35  * The central function of the tracing_map API is
  36  * tracing_map_insert().  tracing_map_insert() hashes the
  37  * arbitrarily-sized key passed into it into a 32-bit unsigned key.
  38  * It then uses this key, truncated to the array size, as an index
  39  * into the array of tracing_map_entries.  If the value of the 'key'
  40  * field of the tracing_map_entry found at that location is 0, then
  41  * that entry is considered to be free and can be claimed, by
  42  * replacing the 0 in the 'key' field of the tracing_map_entry with
  43  * the new 32-bit hashed key.  Once claimed, that tracing_map_entry's
  44  * 'val' field is then used to store a unique element which will be
  45  * forever associated with that 32-bit hashed key in the
  46  * tracing_map_entry.
  47  *
  48  * That unique element now in the tracing_map_entry's 'val' field is
  49  * an instance of tracing_map_elt, where 'elt' in the latter part of
  50  * that variable name is short for 'element'.  The purpose of a
  51  * tracing_map_elt is to hold values specific to the particular
  52  * 32-bit hashed key it's assocated with.  Things such as the unique
  53  * set of aggregated sums associated with the 32-bit hashed key, along
  54  * with a copy of the full key associated with the entry, and which
  55  * was used to produce the 32-bit hashed key.
  56  *
  57  * When tracing_map_create() is called to create the tracing map, the
  58  * user specifies (indirectly via the map_bits param, the details are
  59  * unimportant for this discussion) the maximum number of elements
  60  * that the map can hold (stored in the max_elts field of struct
  61  * tracing_map).  This is the maximum possible number of
  62  * tracing_map_entries in the tracing_map_entry array which can be
  63  * 'claimed' as described in the above discussion, and therefore is
  64  * also the maximum number of tracing_map_elts that can be associated
  65  * with the tracing_map_entry array in the tracing_map.  Because of
  66  * the way the insertion algorithm works, the size of the allocated
  67  * tracing_map_entry array is always twice the maximum number of
  68  * elements (2 * max_elts).  This value is stored in the map_size
  69  * field of struct tracing_map.
  70  *
  71  * Because tracing_map_insert() needs to work from any context,
  72  * including from within the memory allocation functions themselves,
  73  * both the tracing_map_entry array and a pool of max_elts
  74  * tracing_map_elts are pre-allocated before any call is made to
  75  * tracing_map_insert().
  76  *
  77  * The tracing_map_entry array is allocated as a single block by
  78  * tracing_map_create().
  79  *
  80  * Because the tracing_map_elts are much larger objects and can't
  81  * generally be allocated together as a single large array without
  82  * failure, they're allocated individually, by tracing_map_init().
  83  *
  84  * The pool of tracing_map_elts are allocated by tracing_map_init()
  85  * rather than by tracing_map_create() because at the time
  86  * tracing_map_create() is called, there isn't enough information to
  87  * create the tracing_map_elts.  Specifically,the user first needs to
  88  * tell the tracing_map implementation how many fields the
  89  * tracing_map_elts contain, and which types of fields they are (key
  90  * or sum).  The user does this via the tracing_map_add_sum_field()
  91  * and tracing_map_add_key_field() functions, following which the user
  92  * calls tracing_map_init() to finish up the tracing map setup.  The
  93  * array holding the pointers which make up the pre-allocated pool of
  94  * tracing_map_elts is allocated as a single block and is stored in
  95  * the elts field of struct tracing_map.
  96  *
  97  * There is also a set of structures used for sorting that might
  98  * benefit from some minimal explanation.
  99  *
 100  * struct tracing_map_sort_key is used to drive the sort at any given
 101  * time.  By 'any given time' we mean that a different
 102  * tracing_map_sort_key will be used at different times depending on
 103  * whether the sort currently being performed is a primary or a
 104  * secondary sort.
 105  *
 106  * The sort key is very simple, consisting of the field index of the
 107  * tracing_map_elt field to sort on (which the user saved when adding
 108  * the field), and whether the sort should be done in an ascending or
 109  * descending order.
 110  *
 111  * For the convenience of the sorting code, a tracing_map_sort_entry
 112  * is created for each tracing_map_elt, again individually allocated
 113  * to avoid failures that might be expected if allocated as a single
 114  * large array of struct tracing_map_sort_entry.
 115  * tracing_map_sort_entry instances are the objects expected by the
 116  * various internal sorting functions, and are also what the user
 117  * ultimately receives after calling tracing_map_sort_entries().
 118  * Because it doesn't make sense for users to access an unordered and
 119  * sparsely populated tracing_map directly, the
 120  * tracing_map_sort_entries() function is provided so that users can
 121  * retrieve a sorted list of all existing elements.  In addition to
 122  * the associated tracing_map_elt 'elt' field contained within the
 123  * tracing_map_sort_entry, which is the object of interest to the
 124  * user, tracing_map_sort_entry objects contain a number of additional
 125  * fields which are used for caching and internal purposes and can
 126  * safely be ignored.
 127 */
 128
 129 struct tracing_map_field {
 130         tracing_map_cmp_fn_t            cmp_fn;
 131         union {
 132                 atomic64_t                      sum;
 133                 unsigned int                    offset;
 134         };
 135 };
 136
 137 struct tracing_map_elt {
 138         struct tracing_map              *map;
 139         struct tracing_map_field        *fields;
 140         void                            *key;
 141         void                            *private_data;
 142 };
 143
 144 struct tracing_map_entry {
 145         u32                             key;
 146         struct tracing_map_elt          *val;
 147 };
 148
 149 struct tracing_map_sort_key {
 150         unsigned int                    field_idx;
 151         bool                            descending;
 152 };
 153
 154 struct tracing_map_sort_entry {
 155         void                            *key;
 156         struct tracing_map_elt          *elt;
 157         bool                            elt_copied;
 158         bool                            dup;
 159 };
 160
 161 struct tracing_map_array {
 162         unsigned int entries_per_page;
 163         unsigned int entry_size_shift;
 164         unsigned int entry_shift;
 165         unsigned int entry_mask;
 166         unsigned int n_pages;
 167         void **pages;
 168 };
 169
 170 #define TRACING_MAP_ARRAY_ELT(array, idx)                               \
 171         (array->pages[idx >> array->entry_shift] +                      \
 172          ((idx & array->entry_mask) << array->entry_size_shift))
 173
 174 #define TRACING_MAP_ENTRY(array, idx)                                   \
 175         ((struct tracing_map_entry *)TRACING_MAP_ARRAY_ELT(array, idx))
 176
 177 #define TRACING_MAP_ELT(array, idx)                                     \
 178         ((struct tracing_map_elt **)TRACING_MAP_ARRAY_ELT(array, idx))
 179
 180 struct tracing_map {
 181         unsigned int                    key_size;
 182         unsigned int                    map_bits;
 183         unsigned int                    map_size;
 184         unsigned int                    max_elts;
 185         atomic_t                        next_elt;
 186         struct tracing_map_array        *elts;
 187         struct tracing_map_array        *map;
 188         const struct tracing_map_ops    *ops;
 189         void                            *private_data;
 190         struct tracing_map_field        fields[TRACING_MAP_FIELDS_MAX];
 191         unsigned int                    n_fields;
 192         int                             key_idx[TRACING_MAP_KEYS_MAX];
 193         unsigned int                    n_keys;
 194         struct tracing_map_sort_key     sort_key;
 195         atomic64_t                      hits;
 196         atomic64_t                      drops;
 197 };
 198
 199 /**
 200  * struct tracing_map_ops - callbacks for tracing_map
 201  *
 202  * The methods in this structure define callback functions for various
 203  * operations on a tracing_map or objects related to a tracing_map.
 204  *
 205  * For a detailed description of tracing_map_elt objects please see
 206  * the overview of tracing_map data structures at the beginning of
 207  * this file.
 208  *
 209  * All the methods below are optional.
 210  *
 211  * @elt_alloc: When a tracing_map_elt is allocated, this function, if
 212  *      defined, will be called and gives clients the opportunity to
 213  *      allocate additional data and attach it to the element
 214  *      (tracing_map_elt->private_data is meant for that purpose).
 215  *      Element allocation occurs before tracing begins, when the
 216  *      tracing_map_init() call is made by client code.
 217  *
 218  * @elt_copy: At certain points in the lifetime of an element, it may
 219  *      need to be copied.  The copy should include a copy of the
 220  *      client-allocated data, which can be copied into the 'to'
 221  *      element from the 'from' element.
 222  *
 223  * @elt_free: When a tracing_map_elt is freed, this function is called
 224  *      and allows client-allocated per-element data to be freed.
 225  *
 226  * @elt_clear: This callback allows per-element client-defined data to
 227  *      be cleared, if applicable.
 228  *
 229  * @elt_init: This callback allows per-element client-defined data to
 230  *      be initialized when used i.e. when the element is actually
 231  *      claimed by tracing_map_insert() in the context of the map
 232  *      insertion.
 233  */
 234 struct tracing_map_ops {
 235         int                     (*elt_alloc)(struct tracing_map_elt *elt);
 236         void                    (*elt_copy)(struct tracing_map_elt *to,
 237                                             struct tracing_map_elt *from);
 238         void                    (*elt_free)(struct tracing_map_elt *elt);
 239         void                    (*elt_clear)(struct tracing_map_elt *elt);
 240         void                    (*elt_init)(struct tracing_map_elt *elt);
 241 };
 242
 243 extern struct tracing_map *
 244 tracing_map_create(unsigned int map_bits,
 245                    unsigned int key_size,
 246                    const struct tracing_map_ops *ops,
 247                    void *private_data);
 248 extern int tracing_map_init(struct tracing_map *map);
 249
 250 extern int tracing_map_add_sum_field(struct tracing_map *map);
 251 extern int tracing_map_add_key_field(struct tracing_map *map,
 252                                      unsigned int offset,
 253                                      tracing_map_cmp_fn_t cmp_fn);
 254
 255 extern void tracing_map_destroy(struct tracing_map *map);
 256 extern void tracing_map_clear(struct tracing_map *map);
 257
 258 extern struct tracing_map_elt *
 259 tracing_map_insert(struct tracing_map *map, void *key);
 260 extern struct tracing_map_elt *
 261 tracing_map_lookup(struct tracing_map *map, void *key);
 262
 263 extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size,
 264                                                 int field_is_signed);
 265 extern int tracing_map_cmp_string(void *val_a, void *val_b);
 266 extern int tracing_map_cmp_none(void *val_a, void *val_b);
 267
 268 extern void tracing_map_update_sum(struct tracing_map_elt *elt,
 269                                    unsigned int i, u64 n);
 270 extern u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i);
 271 extern void tracing_map_set_field_descr(struct tracing_map *map,
 272                                         unsigned int i,
 273                                         unsigned int key_offset,
 274                                         tracing_map_cmp_fn_t cmp_fn);
 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 */