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