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288 lines
11 KiB
288 lines
11 KiB
// SPDX-License-Identifier: GPL-2.0 |
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#ifndef __TRACING_MAP_H |
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#define __TRACING_MAP_H |
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#define TRACING_MAP_BITS_DEFAULT 11 |
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#define TRACING_MAP_BITS_MAX 17 |
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#define TRACING_MAP_BITS_MIN 7 |
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#define TRACING_MAP_KEYS_MAX 3 |
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#define TRACING_MAP_VALS_MAX 3 |
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#define TRACING_MAP_FIELDS_MAX (TRACING_MAP_KEYS_MAX + \ |
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TRACING_MAP_VALS_MAX) |
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#define TRACING_MAP_VARS_MAX 16 |
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#define TRACING_MAP_SORT_KEYS_MAX 2 |
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typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b); |
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/* |
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* This is an overview of the tracing_map data structures and how they |
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* relate to the tracing_map API. The details of the algorithms |
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* aren't discussed here - this is just a general overview of the data |
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* structures and how they interact with the API. |
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* |
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* The central data structure of the tracing_map is an initially |
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* zeroed array of struct tracing_map_entry (stored in the map field |
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* of struct tracing_map). tracing_map_entry is a very simple data |
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* structure containing only two fields: a 32-bit unsigned 'key' |
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* variable and a pointer named 'val'. This array of struct |
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* tracing_map_entry is essentially a hash table which will be |
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* modified by a single function, tracing_map_insert(), but which can |
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* be traversed and read by a user at any time (though the user does |
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* this indirectly via an array of tracing_map_sort_entry - see the |
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* explanation of that data structure in the discussion of the |
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* sorting-related data structures below). |
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* |
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* The central function of the tracing_map API is |
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* tracing_map_insert(). tracing_map_insert() hashes the |
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* arbitrarily-sized key passed into it into a 32-bit unsigned key. |
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* It then uses this key, truncated to the array size, as an index |
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* into the array of tracing_map_entries. If the value of the 'key' |
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* field of the tracing_map_entry found at that location is 0, then |
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* that entry is considered to be free and can be claimed, by |
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* replacing the 0 in the 'key' field of the tracing_map_entry with |
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* the new 32-bit hashed key. Once claimed, that tracing_map_entry's |
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* 'val' field is then used to store a unique element which will be |
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* forever associated with that 32-bit hashed key in the |
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* tracing_map_entry. |
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* |
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* That unique element now in the tracing_map_entry's 'val' field is |
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* an instance of tracing_map_elt, where 'elt' in the latter part of |
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* that variable name is short for 'element'. The purpose of a |
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* tracing_map_elt is to hold values specific to the particular |
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* 32-bit hashed key it's associated with. Things such as the unique |
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* set of aggregated sums associated with the 32-bit hashed key, along |
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* with a copy of the full key associated with the entry, and which |
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* was used to produce the 32-bit hashed key. |
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* |
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* When tracing_map_create() is called to create the tracing map, the |
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* user specifies (indirectly via the map_bits param, the details are |
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* unimportant for this discussion) the maximum number of elements |
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* that the map can hold (stored in the max_elts field of struct |
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* tracing_map). This is the maximum possible number of |
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* tracing_map_entries in the tracing_map_entry array which can be |
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* 'claimed' as described in the above discussion, and therefore is |
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* also the maximum number of tracing_map_elts that can be associated |
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* with the tracing_map_entry array in the tracing_map. Because of |
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* the way the insertion algorithm works, the size of the allocated |
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* tracing_map_entry array is always twice the maximum number of |
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* elements (2 * max_elts). This value is stored in the map_size |
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* field of struct tracing_map. |
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* |
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* Because tracing_map_insert() needs to work from any context, |
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* including from within the memory allocation functions themselves, |
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* both the tracing_map_entry array and a pool of max_elts |
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* tracing_map_elts are pre-allocated before any call is made to |
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* tracing_map_insert(). |
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* |
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* The tracing_map_entry array is allocated as a single block by |
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* tracing_map_create(). |
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* |
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* Because the tracing_map_elts are much larger objects and can't |
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* generally be allocated together as a single large array without |
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* failure, they're allocated individually, by tracing_map_init(). |
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* |
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* The pool of tracing_map_elts are allocated by tracing_map_init() |
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* rather than by tracing_map_create() because at the time |
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* tracing_map_create() is called, there isn't enough information to |
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* create the tracing_map_elts. Specifically,the user first needs to |
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* tell the tracing_map implementation how many fields the |
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* tracing_map_elts contain, and which types of fields they are (key |
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* or sum). The user does this via the tracing_map_add_sum_field() |
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* and tracing_map_add_key_field() functions, following which the user |
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* calls tracing_map_init() to finish up the tracing map setup. The |
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* array holding the pointers which make up the pre-allocated pool of |
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* tracing_map_elts is allocated as a single block and is stored in |
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* the elts field of struct tracing_map. |
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* |
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* There is also a set of structures used for sorting that might |
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* benefit from some minimal explanation. |
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* |
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* struct tracing_map_sort_key is used to drive the sort at any given |
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* time. By 'any given time' we mean that a different |
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* tracing_map_sort_key will be used at different times depending on |
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* whether the sort currently being performed is a primary or a |
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* secondary sort. |
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* |
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* The sort key is very simple, consisting of the field index of the |
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* tracing_map_elt field to sort on (which the user saved when adding |
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* the field), and whether the sort should be done in an ascending or |
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* descending order. |
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* |
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* For the convenience of the sorting code, a tracing_map_sort_entry |
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* is created for each tracing_map_elt, again individually allocated |
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* to avoid failures that might be expected if allocated as a single |
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* large array of struct tracing_map_sort_entry. |
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* tracing_map_sort_entry instances are the objects expected by the |
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* various internal sorting functions, and are also what the user |
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* ultimately receives after calling tracing_map_sort_entries(). |
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* Because it doesn't make sense for users to access an unordered and |
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* sparsely populated tracing_map directly, the |
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* tracing_map_sort_entries() function is provided so that users can |
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* retrieve a sorted list of all existing elements. In addition to |
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* the associated tracing_map_elt 'elt' field contained within the |
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* tracing_map_sort_entry, which is the object of interest to the |
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* user, tracing_map_sort_entry objects contain a number of additional |
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* fields which are used for caching and internal purposes and can |
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* safely be ignored. |
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*/ |
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struct tracing_map_field { |
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tracing_map_cmp_fn_t cmp_fn; |
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union { |
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atomic64_t sum; |
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unsigned int offset; |
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}; |
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}; |
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struct tracing_map_elt { |
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struct tracing_map *map; |
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struct tracing_map_field *fields; |
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atomic64_t *vars; |
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bool *var_set; |
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void *key; |
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void *private_data; |
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}; |
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struct tracing_map_entry { |
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u32 key; |
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struct tracing_map_elt *val; |
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}; |
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struct tracing_map_sort_key { |
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unsigned int field_idx; |
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bool descending; |
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}; |
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struct tracing_map_sort_entry { |
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void *key; |
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struct tracing_map_elt *elt; |
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bool elt_copied; |
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bool dup; |
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}; |
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struct tracing_map_array { |
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unsigned int entries_per_page; |
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unsigned int entry_size_shift; |
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unsigned int entry_shift; |
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unsigned int entry_mask; |
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unsigned int n_pages; |
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void **pages; |
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}; |
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#define TRACING_MAP_ARRAY_ELT(array, idx) \ |
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(array->pages[idx >> array->entry_shift] + \ |
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((idx & array->entry_mask) << array->entry_size_shift)) |
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#define TRACING_MAP_ENTRY(array, idx) \ |
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((struct tracing_map_entry *)TRACING_MAP_ARRAY_ELT(array, idx)) |
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#define TRACING_MAP_ELT(array, idx) \ |
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((struct tracing_map_elt **)TRACING_MAP_ARRAY_ELT(array, idx)) |
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struct tracing_map { |
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unsigned int key_size; |
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unsigned int map_bits; |
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unsigned int map_size; |
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unsigned int max_elts; |
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atomic_t next_elt; |
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struct tracing_map_array *elts; |
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struct tracing_map_array *map; |
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const struct tracing_map_ops *ops; |
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void *private_data; |
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struct tracing_map_field fields[TRACING_MAP_FIELDS_MAX]; |
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unsigned int n_fields; |
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int key_idx[TRACING_MAP_KEYS_MAX]; |
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unsigned int n_keys; |
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struct tracing_map_sort_key sort_key; |
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unsigned int n_vars; |
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atomic64_t hits; |
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atomic64_t drops; |
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}; |
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/** |
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* struct tracing_map_ops - callbacks for tracing_map |
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* |
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* The methods in this structure define callback functions for various |
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* operations on a tracing_map or objects related to a tracing_map. |
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* |
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* For a detailed description of tracing_map_elt objects please see |
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* the overview of tracing_map data structures at the beginning of |
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* this file. |
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* |
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* All the methods below are optional. |
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* |
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* @elt_alloc: When a tracing_map_elt is allocated, this function, if |
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* defined, will be called and gives clients the opportunity to |
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* allocate additional data and attach it to the element |
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* (tracing_map_elt->private_data is meant for that purpose). |
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* Element allocation occurs before tracing begins, when the |
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* tracing_map_init() call is made by client code. |
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* |
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* @elt_free: When a tracing_map_elt is freed, this function is called |
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* and allows client-allocated per-element data to be freed. |
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* |
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* @elt_clear: This callback allows per-element client-defined data to |
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* be cleared, if applicable. |
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* |
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* @elt_init: This callback allows per-element client-defined data to |
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* be initialized when used i.e. when the element is actually |
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* claimed by tracing_map_insert() in the context of the map |
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* insertion. |
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*/ |
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struct tracing_map_ops { |
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int (*elt_alloc)(struct tracing_map_elt *elt); |
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void (*elt_free)(struct tracing_map_elt *elt); |
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void (*elt_clear)(struct tracing_map_elt *elt); |
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void (*elt_init)(struct tracing_map_elt *elt); |
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}; |
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extern struct tracing_map * |
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tracing_map_create(unsigned int map_bits, |
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unsigned int key_size, |
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const struct tracing_map_ops *ops, |
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void *private_data); |
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extern int tracing_map_init(struct tracing_map *map); |
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extern int tracing_map_add_sum_field(struct tracing_map *map); |
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extern int tracing_map_add_var(struct tracing_map *map); |
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extern int tracing_map_add_key_field(struct tracing_map *map, |
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unsigned int offset, |
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tracing_map_cmp_fn_t cmp_fn); |
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extern void tracing_map_destroy(struct tracing_map *map); |
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extern void tracing_map_clear(struct tracing_map *map); |
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extern struct tracing_map_elt * |
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tracing_map_insert(struct tracing_map *map, void *key); |
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extern struct tracing_map_elt * |
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tracing_map_lookup(struct tracing_map *map, void *key); |
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extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size, |
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int field_is_signed); |
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extern int tracing_map_cmp_string(void *val_a, void *val_b); |
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extern int tracing_map_cmp_none(void *val_a, void *val_b); |
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extern void tracing_map_update_sum(struct tracing_map_elt *elt, |
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unsigned int i, u64 n); |
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extern void tracing_map_set_var(struct tracing_map_elt *elt, |
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unsigned int i, u64 n); |
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extern bool tracing_map_var_set(struct tracing_map_elt *elt, unsigned int i); |
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extern u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i); |
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extern u64 tracing_map_read_var(struct tracing_map_elt *elt, unsigned int i); |
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extern u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i); |
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extern void tracing_map_set_field_descr(struct tracing_map *map, |
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unsigned int i, |
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unsigned int key_offset, |
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tracing_map_cmp_fn_t cmp_fn); |
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extern int |
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tracing_map_sort_entries(struct tracing_map *map, |
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struct tracing_map_sort_key *sort_keys, |
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unsigned int n_sort_keys, |
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struct tracing_map_sort_entry ***sort_entries); |
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extern void |
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tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries, |
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unsigned int n_entries); |
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#endif /* __TRACING_MAP_H */
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