tracing: Add per-element variable support to tracing_map
In order to allow information to be passed between trace events, add support for per-element variables to tracing_map. This provides a means for histograms to associate a value or values with an entry when it's saved or updated, and retrieved by a subsequent event occurrences. Variables can be set using tracing_map_set_var() and read using tracing_map_read_var(). tracing_map_var_set() returns true or false depending on whether or not the variable has been set or not, which is important for event-matching applications. tracing_map_read_var_once() reads the variable and resets it to the 'unset' state, implementing read-once variables, which are also important for event-matching uses. Link: http://lkml.kernel.org/r/7fa001108252556f0c6dd9d63145eabfe3370d1a.1516069914.git.tom.zanussi@linux.intel.com Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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@ -66,6 +66,73 @@ u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i)
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return (u64)atomic64_read(&elt->fields[i].sum);
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}
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/**
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* tracing_map_set_var - Assign a tracing_map_elt's variable field
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* @elt: The tracing_map_elt
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* @i: The index of the given variable associated with the tracing_map_elt
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* @n: The value to assign
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*
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* Assign n to variable i associated with the specified tracing_map_elt
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* instance. The index i is the index returned by the call to
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* tracing_map_add_var() when the tracing map was set up.
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*/
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void tracing_map_set_var(struct tracing_map_elt *elt, unsigned int i, u64 n)
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{
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atomic64_set(&elt->vars[i], n);
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elt->var_set[i] = true;
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}
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/**
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* tracing_map_var_set - Return whether or not a variable has been set
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* @elt: The tracing_map_elt
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* @i: The index of the given variable associated with the tracing_map_elt
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*
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* Return true if the variable has been set, false otherwise. The
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* index i is the index returned by the call to tracing_map_add_var()
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* when the tracing map was set up.
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*/
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bool tracing_map_var_set(struct tracing_map_elt *elt, unsigned int i)
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{
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return elt->var_set[i];
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}
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/**
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* tracing_map_read_var - Return the value of a tracing_map_elt's variable field
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* @elt: The tracing_map_elt
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* @i: The index of the given variable associated with the tracing_map_elt
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*
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* Retrieve the value of the variable i associated with the specified
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* tracing_map_elt instance. The index i is the index returned by the
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* call to tracing_map_add_var() when the tracing map was set
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* up.
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*
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* Return: The variable value associated with field i for elt.
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*/
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u64 tracing_map_read_var(struct tracing_map_elt *elt, unsigned int i)
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{
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return (u64)atomic64_read(&elt->vars[i]);
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}
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/**
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* tracing_map_read_var_once - Return and reset a tracing_map_elt's variable field
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* @elt: The tracing_map_elt
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* @i: The index of the given variable associated with the tracing_map_elt
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*
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* Retrieve the value of the variable i associated with the specified
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* tracing_map_elt instance, and reset the variable to the 'not set'
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* state. The index i is the index returned by the call to
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* tracing_map_add_var() when the tracing map was set up. The reset
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* essentially makes the variable a read-once variable if it's only
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* accessed using this function.
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*
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* Return: The variable value associated with field i for elt.
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*/
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u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i)
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{
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elt->var_set[i] = false;
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return (u64)atomic64_read(&elt->vars[i]);
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}
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int tracing_map_cmp_string(void *val_a, void *val_b)
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{
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char *a = val_a;
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@ -170,6 +237,28 @@ int tracing_map_add_sum_field(struct tracing_map *map)
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return tracing_map_add_field(map, tracing_map_cmp_atomic64);
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}
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/**
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* tracing_map_add_var - Add a field describing a tracing_map var
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* @map: The tracing_map
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*
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* Add a var to the map and return the index identifying it in the map
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* and associated tracing_map_elts. This is the index used for
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* instance to update a var for a particular tracing_map_elt using
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* tracing_map_update_var() or reading it via tracing_map_read_var().
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*
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* Return: The index identifying the var in the map and associated
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* tracing_map_elts, or -EINVAL on error.
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*/
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int tracing_map_add_var(struct tracing_map *map)
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{
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int ret = -EINVAL;
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if (map->n_vars < TRACING_MAP_VARS_MAX)
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ret = map->n_vars++;
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return ret;
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}
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/**
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* tracing_map_add_key_field - Add a field describing a tracing_map key
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* @map: The tracing_map
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@ -280,6 +369,11 @@ static void tracing_map_elt_clear(struct tracing_map_elt *elt)
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if (elt->fields[i].cmp_fn == tracing_map_cmp_atomic64)
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atomic64_set(&elt->fields[i].sum, 0);
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for (i = 0; i < elt->map->n_vars; i++) {
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atomic64_set(&elt->vars[i], 0);
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elt->var_set[i] = false;
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}
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if (elt->map->ops && elt->map->ops->elt_clear)
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elt->map->ops->elt_clear(elt);
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}
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@ -306,6 +400,8 @@ static void tracing_map_elt_free(struct tracing_map_elt *elt)
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if (elt->map->ops && elt->map->ops->elt_free)
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elt->map->ops->elt_free(elt);
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kfree(elt->fields);
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kfree(elt->vars);
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kfree(elt->var_set);
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kfree(elt->key);
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kfree(elt);
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}
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@ -333,6 +429,18 @@ static struct tracing_map_elt *tracing_map_elt_alloc(struct tracing_map *map)
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goto free;
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}
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elt->vars = kcalloc(map->n_vars, sizeof(*elt->vars), GFP_KERNEL);
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if (!elt->vars) {
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err = -ENOMEM;
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goto free;
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}
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elt->var_set = kcalloc(map->n_vars, sizeof(*elt->var_set), GFP_KERNEL);
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if (!elt->var_set) {
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err = -ENOMEM;
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goto free;
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}
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tracing_map_elt_init_fields(elt);
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if (map->ops && map->ops->elt_alloc) {
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@ -10,6 +10,7 @@
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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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@ -137,6 +138,8 @@ struct tracing_map_field {
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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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@ -192,6 +195,7 @@ struct tracing_map {
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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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@ -241,6 +245,7 @@ tracing_map_create(unsigned int map_bits,
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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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@ -260,7 +265,13 @@ 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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