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#ifndef TR2_CTR_H
#define TR2_CTR_H
#include "trace2.h"
#include "trace2/tr2_tgt.h"
/*
* Define a mechanism to allow global "counters".
*
* Counters can be used count interesting activity that does not fit
* the "region and data" model, such as code called from many
* different regions and/or where you want to count a number of items,
* but don't have control of when the last item will be processed,
* such as counter the number of calls to `lstat()`.
*
* Counters differ from Trace2 "data" events. Data events are emitted
* immediately and are appropriate for documenting loop counters at
* the end of a region, for example. Counter values are accumulated
* during the program and final counter values are emitted at program
* exit.
*
* To make this model efficient, we define a compile-time fixed set of
* counters and counter ids using a fixed size "counter block" array
* in thread-local storage. This gives us constant time, lock-free
* access to each counter within each thread. This lets us avoid the
* complexities of dynamically allocating a counter and sharing that
* definition with other threads.
*
* Each thread uses the counter block in its thread-local storage to
* increment partial sums for each counter (without locking). When a
* thread exits, those partial sums are (under lock) added to the
* global final sum.
*
* Partial sums for each counter are optionally emitted when a thread
* exits.
*
* Final sums for each counter are emitted between the "exit" and
* "atexit" events.
*
* A parallel "counter metadata" table contains the "category" and
* "name" fields for each counter. This eliminates the need to
* include those args in the various counter APIs.
*/
/*
* The definition of an individual counter as used by an individual
* thread (and later in aggregation).
*/
struct tr2_counter {
uint64_t value;
};
/*
* Metadata for a counter.
*/
struct tr2_counter_metadata {
const char *category;
const char *name;
/*
* True if we should emit per-thread events for this counter
* when individual threads exit.
*/
unsigned int want_per_thread_events:1;
};
/*
* A compile-time fixed block of counters to insert into thread-local
* storage. This wrapper is used to avoid quirks of C and the usual
* need to pass an array size argument.
*/
struct tr2_counter_block {
struct tr2_counter counter[TRACE2_NUMBER_OF_COUNTERS];
};
/*
* Private routines used by trace2.c to increment a counter for the
* current thread.
*/
void tr2_counter_increment(enum trace2_counter_id cid, uint64_t value);
/*
* Add the current thread's counter data to the global totals.
* This is called during thread-exit.
*
* Caller must be holding the tr2tls_mutex.
*/
void tr2_update_final_counters(void);
/*
* Emit per-thread counter data for the current thread.
* This is called during thread-exit.
*/
void tr2_emit_per_thread_counters(tr2_tgt_evt_counter_t *fn_apply);
/*
* Emit global counter values.
* This is called during atexit handling.
*
* Caller must be holding the tr2tls_mutex.
*/
void tr2_emit_final_counters(tr2_tgt_evt_counter_t *fn_apply);
#endif /* TR2_CTR_H */
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