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284 lines
11 KiB
284 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 2
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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_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 assocated 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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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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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_copy: At certain points in the lifetime of an element, it may
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* need to be copied. The copy should include a copy of the
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* client-allocated data, which can be copied into the 'to'
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* element from the 'from' element.
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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_copy)(struct tracing_map_elt *to,
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struct tracing_map_elt *from);
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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_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 u64 tracing_map_read_sum(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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