kernel/trace/tracing_map.h

   1 #ifndef __TRACING_MAP_H
   2 #define __TRACING_MAP_H
   3
   4 #define TRACING_MAP_BITS_DEFAULT        11
   5 #define TRACING_MAP_BITS_MAX            17
   6 #define TRACING_MAP_BITS_MIN            7
   7
   8 #define TRACING_MAP_FIELDS_MAX          4
   9 #define TRACING_MAP_KEYS_MAX            2
  10
  11 #define TRACING_MAP_SORT_KEYS_MAX       2
  12
  13 typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b);
  14
  15 /*
  16  * This is an overview of the tracing_map data structures and how they
  17  * relate to the tracing_map API.  The details of the algorithms
  18  * aren't discussed here - this is just a general overview of the data
  19  * structures and how they interact with the API.
  20  *
  21  * The central data structure of the tracing_map is an initially
  22  * zeroed array of struct tracing_map_entry (stored in the map field
  23  * of struct tracing_map).  tracing_map_entry is a very simple data
  24  * structure containing only two fields: a 32-bit unsigned 'key'
  25  * variable and a pointer named 'val'.  This array of struct
  26  * tracing_map_entry is essentially a hash table which will be
  27  * modified by a single function, tracing_map_insert(), but which can
  28  * be traversed and read by a user at any time (though the user does
  29  * this indirectly via an array of tracing_map_sort_entry - see the
  30  * explanation of that data structure in the discussion of the
  31  * sorting-related data structures below).
  32  *
  33  * The central function of the tracing_map API is
  34  * tracing_map_insert().  tracing_map_insert() hashes the
  35  * arbitrarily-sized key passed into it into a 32-bit unsigned key.
  36  * It then uses this key, truncated to the array size, as an index
  37  * into the array of tracing_map_entries.  If the value of the 'key'
  38  * field of the tracing_map_entry found at that location is 0, then
  39  * that entry is considered to be free and can be claimed, by
  40  * replacing the 0 in the 'key' field of the tracing_map_entry with
  41  * the new 32-bit hashed key.  Once claimed, that tracing_map_entry's
  42  * 'val' field is then used to store a unique element which will be
  43  * forever associated with that 32-bit hashed key in the
  44  * tracing_map_entry.
  45  *
  46  * That unique element now in the tracing_map_entry's 'val' field is
  47  * an instance of tracing_map_elt, where 'elt' in the latter part of
  48  * that variable name is short for 'element'.  The purpose of a
  49  * tracing_map_elt is to hold values specific to the the particular
  50  * 32-bit hashed key it's assocated with.  Things such as the unique
  51  * set of aggregated sums associated with the 32-bit hashed key, along
  52  * with a copy of the full key associated with the entry, and which
  53  * was used to produce the 32-bit hashed key.
  54  *
  55  * When tracing_map_create() is called to create the tracing map, the
  56  * user specifies (indirectly via the map_bits param, the details are
  57  * unimportant for this discussion) the maximum number of elements
  58  * that the map can hold (stored in the max_elts field of struct
  59  * tracing_map).  This is the maximum possible number of
  60  * tracing_map_entries in the tracing_map_entry array which can be
  61  * 'claimed' as described in the above discussion, and therefore is
  62  * also the maximum number of tracing_map_elts that can be associated
  63  * with the tracing_map_entry array in the tracing_map.  Because of
  64  * the way the insertion algorithm works, the size of the allocated
  65  * tracing_map_entry array is always twice the maximum number of
  66  * elements (2 * max_elts).  This value is stored in the map_size
  67  * field of struct tracing_map.
  68  *
  69  * Because tracing_map_insert() needs to work from any context,
  70  * including from within the memory allocation functions themselves,
  71  * both the tracing_map_entry array and a pool of max_elts
  72  * tracing_map_elts are pre-allocated before any call is made to
  73  * tracing_map_insert().
  74  *
  75  * The tracing_map_entry array is allocated as a single block by
  76  * tracing_map_create().
  77  *
  78  * Because the tracing_map_elts are much larger objects and can't
  79  * generally be allocated together as a single large array without
  80  * failure, they're allocated individually, by tracing_map_init().
  81  *
  82  * The pool of tracing_map_elts are allocated by tracing_map_init()
  83  * rather than by tracing_map_create() because at the time
  84  * tracing_map_create() is called, there isn't enough information to
  85  * create the tracing_map_elts.  Specifically,the user first needs to
  86  * tell the tracing_map implementation how many fields the
  87  * tracing_map_elts contain, and which types of fields they are (key
  88  * or sum).  The user does this via the tracing_map_add_sum_field()
  89  * and tracing_map_add_key_field() functions, following which the user
  90  * calls tracing_map_init() to finish up the tracing map setup.  The
  91  * array holding the pointers which make up the pre-allocated pool of
  92  * tracing_map_elts is allocated as a single block and is stored in
  93  * the elts field of struct tracing_map.
  94  *
  95  * There is also a set of structures used for sorting that might
  96  * benefit from some minimal explanation.
  97  *
  98  * struct tracing_map_sort_key is used to drive the sort at any given
  99  * time.  By 'any given time' we mean that a different
 100  * tracing_map_sort_key will be used at different times depending on
 101  * whether the sort currently being performed is a primary or a
 102  * secondary sort.
 103  *
 104  * The sort key is very simple, consisting of the field index of the
 105  * tracing_map_elt field to sort on (which the user saved when adding
 106  * the field), and whether the sort should be done in an ascending or
 107  * descending order.
 108  *
 109  * For the convenience of the sorting code, a tracing_map_sort_entry
 110  * is created for each tracing_map_elt, again individually allocated
 111  * to avoid failures that might be expected if allocated as a single
 112  * large array of struct tracing_map_sort_entry.
 113  * tracing_map_sort_entry instances are the objects expected by the
 114  * various internal sorting functions, and are also what the user
 115  * ultimately receives after calling tracing_map_sort_entries().
 116  * Because it doesn't make sense for users to access an unordered and
 117  * sparsely populated tracing_map directly, the
 118  * tracing_map_sort_entries() function is provided so that users can
 119  * retrieve a sorted list of all existing elements.  In addition to
 120  * the associated tracing_map_elt 'elt' field contained within the
 121  * tracing_map_sort_entry, which is the object of interest to the
 122  * user, tracing_map_sort_entry objects contain a number of additional
 123  * fields which are used for caching and internal purposes and can
 124  * safely be ignored.
 125 */
 126
 127 struct tracing_map_field {
 128         tracing_map_cmp_fn_t            cmp_fn;
 129         union {
 130                 atomic64_t                      sum;
 131                 unsigned int                    offset;
 132         };
 133 };
 134
 135 struct tracing_map_elt {
 136         struct tracing_map              *map;
 137         struct tracing_map_field        *fields;
 138         void                            *key;
 139         void                            *private_data;
 140 };
 141
 142 struct tracing_map_entry {
 143         u32                             key;
 144         struct tracing_map_elt          *val;
 145 };
 146
 147 struct tracing_map_sort_key {
 148         unsigned int                    field_idx;
 149         bool                            descending;
 150 };
 151
 152 struct tracing_map_sort_entry {
 153         void                            *key;
 154         struct tracing_map_elt          *elt;
 155         bool                            elt_copied;
 156         bool                            dup;
 157 };
 158
 159 struct tracing_map_array {
 160         unsigned int entries_per_page;
 161         unsigned int entry_size_shift;
 162         unsigned int entry_shift;
 163         unsigned int entry_mask;
 164         unsigned int n_pages;
 165         void **pages;
 166 };
 167
 168 #define TRACING_MAP_ARRAY_ELT(array, idx)                               \
 169         (array->pages[idx >> array->entry_shift] +                      \
 170          ((idx & array->entry_mask) << array->entry_size_shift))
 171
 172 #define TRACING_MAP_ENTRY(array, idx)                                   \
 173         ((struct tracing_map_entry *)TRACING_MAP_ARRAY_ELT(array, idx))
 174
 175 #define TRACING_MAP_ELT(array, idx)                                     \
 176         ((struct tracing_map_elt **)TRACING_MAP_ARRAY_ELT(array, idx))
 177
 178 struct tracing_map {
 179         unsigned int                    key_size;
 180         unsigned int                    map_bits;
 181         unsigned int                    map_size;
 182         unsigned int                    max_elts;
 183         atomic_t                        next_elt;
 184         struct tracing_map_array        *elts;
 185         struct tracing_map_array        *map;
 186         const struct tracing_map_ops    *ops;
 187         void                            *private_data;
 188         struct tracing_map_field        fields[TRACING_MAP_FIELDS_MAX];
 189         unsigned int                    n_fields;
 190         int                             key_idx[TRACING_MAP_KEYS_MAX];
 191         unsigned int                    n_keys;
 192         struct tracing_map_sort_key     sort_key;
 193         atomic64_t                      hits;
 194         atomic64_t                      drops;
 195 };
 196
 197 /**
 198  * struct tracing_map_ops - callbacks for tracing_map
 199  *
 200  * The methods in this structure define callback functions for various
 201  * operations on a tracing_map or objects related to a tracing_map.
 202  *
 203  * For a detailed description of tracing_map_elt objects please see
 204  * the overview of tracing_map data structures at the beginning of
 205  * this file.
 206  *
 207  * All the methods below are optional.
 208  *
 209  * @elt_alloc: When a tracing_map_elt is allocated, this function, if
 210  *      defined, will be called and gives clients the opportunity to
 211  *      allocate additional data and attach it to the element
 212  *      (tracing_map_elt->private_data is meant for that purpose).
 213  *      Element allocation occurs before tracing begins, when the
 214  *      tracing_map_init() call is made by client code.
 215  *
 216  * @elt_copy: At certain points in the lifetime of an element, it may
 217  *      need to be copied.  The copy should include a copy of the
 218  *      client-allocated data, which can be copied into the 'to'
 219  *      element from the 'from' element.
 220  *
 221  * @elt_free: When a tracing_map_elt is freed, this function is called
 222  *      and allows client-allocated per-element data to be freed.
 223  *
 224  * @elt_clear: This callback allows per-element client-defined data to
 225  *      be cleared, if applicable.
 226  *
 227  * @elt_init: This callback allows per-element client-defined data to
 228  *      be initialized when used i.e. when the element is actually
 229  *      claimed by tracing_map_insert() in the context of the map
 230  *      insertion.
 231  */
 232 struct tracing_map_ops {
 233         int                     (*elt_alloc)(struct tracing_map_elt *elt);
 234         void                    (*elt_copy)(struct tracing_map_elt *to,
 235                                             struct tracing_map_elt *from);
 236         void                    (*elt_free)(struct tracing_map_elt *elt);
 237         void                    (*elt_clear)(struct tracing_map_elt *elt);
 238         void                    (*elt_init)(struct tracing_map_elt *elt);
 239 };
 240
 241 extern struct tracing_map *
 242 tracing_map_create(unsigned int map_bits,
 243                    unsigned int key_size,
 244                    const struct tracing_map_ops *ops,
 245                    void *private_data);
 246 extern int tracing_map_init(struct tracing_map *map);
 247
 248 extern int tracing_map_add_sum_field(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 u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i);
 269 extern void tracing_map_set_field_descr(struct tracing_map *map,
 270                                         unsigned int i,
 271                                         unsigned int key_offset,
 272                                         tracing_map_cmp_fn_t cmp_fn);
 273 extern int
 274 tracing_map_sort_entries(struct tracing_map *map,
 275                          struct tracing_map_sort_key *sort_keys,
 276                          unsigned int n_sort_keys,
 277                          struct tracing_map_sort_entry ***sort_entries);
 278
 279 extern void
 280 tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries,
 281                                  unsigned int n_entries);
 282 #endif /* __TRACING_MAP_H */