| 1 | #ifndef TR2_CTR_H |
| 2 | #define TR2_CTR_H |
| 3 | |
| 4 | #include "trace2.h" |
| 5 | #include "trace2/tr2_tgt.h" |
| 6 | |
| 7 | /* |
| 8 | * Define a mechanism to allow global "counters". |
| 9 | * |
| 10 | * Counters can be used count interesting activity that does not fit |
| 11 | * the "region and data" model, such as code called from many |
| 12 | * different regions and/or where you want to count a number of items, |
| 13 | * but don't have control of when the last item will be processed, |
| 14 | * such as counter the number of calls to `lstat()`. |
| 15 | * |
| 16 | * Counters differ from Trace2 "data" events. Data events are emitted |
| 17 | * immediately and are appropriate for documenting loop counters at |
| 18 | * the end of a region, for example. Counter values are accumulated |
| 19 | * during the program and final counter values are emitted at program |
| 20 | * exit. |
| 21 | * |
| 22 | * To make this model efficient, we define a compile-time fixed set of |
| 23 | * counters and counter ids using a fixed size "counter block" array |
| 24 | * in thread-local storage. This gives us constant time, lock-free |
| 25 | * access to each counter within each thread. This lets us avoid the |
| 26 | * complexities of dynamically allocating a counter and sharing that |
| 27 | * definition with other threads. |
| 28 | * |
| 29 | * Each thread uses the counter block in its thread-local storage to |
| 30 | * increment partial sums for each counter (without locking). When a |
| 31 | * thread exits, those partial sums are (under lock) added to the |
| 32 | * global final sum. |
| 33 | * |
| 34 | * Partial sums for each counter are optionally emitted when a thread |
| 35 | * exits. |
| 36 | * |
| 37 | * Final sums for each counter are emitted between the "exit" and |
| 38 | * "atexit" events. |
| 39 | * |
| 40 | * A parallel "counter metadata" table contains the "category" and |
| 41 | * "name" fields for each counter. This eliminates the need to |
| 42 | * include those args in the various counter APIs. |
| 43 | */ |
| 44 | |
| 45 | /* |
| 46 | * The definition of an individual counter as used by an individual |
| 47 | * thread (and later in aggregation). |
| 48 | */ |
| 49 | struct tr2_counter { |
| 50 | uint64_t value; |
| 51 | }; |
| 52 | |
| 53 | /* |
| 54 | * Metadata for a counter. |
| 55 | */ |
| 56 | struct tr2_counter_metadata { |
| 57 | const char *category; |
| 58 | const char *name; |
| 59 | |
| 60 | /* |
| 61 | * True if we should emit per-thread events for this counter |
| 62 | * when individual threads exit. |
| 63 | */ |
| 64 | unsigned int want_per_thread_events:1; |
| 65 | }; |
| 66 | |
| 67 | /* |
| 68 | * A compile-time fixed block of counters to insert into thread-local |
| 69 | * storage. This wrapper is used to avoid quirks of C and the usual |
| 70 | * need to pass an array size argument. |
| 71 | */ |
| 72 | struct tr2_counter_block { |
| 73 | struct tr2_counter counter[TRACE2_NUMBER_OF_COUNTERS]; |
| 74 | }; |
| 75 | |
| 76 | /* |
| 77 | * Private routines used by trace2.c to increment a counter for the |
| 78 | * current thread. |
| 79 | */ |
| 80 | void tr2_counter_increment(enum trace2_counter_id cid, uint64_t value); |
| 81 | |
| 82 | /* |
| 83 | * Add the current thread's counter data to the global totals. |
| 84 | * This is called during thread-exit. |
| 85 | * |
| 86 | * Caller must be holding the tr2tls_mutex. |
| 87 | */ |
| 88 | void tr2_update_final_counters(void); |
| 89 | |
| 90 | /* |
| 91 | * Emit per-thread counter data for the current thread. |
| 92 | * This is called during thread-exit. |
| 93 | */ |
| 94 | void tr2_emit_per_thread_counters(tr2_tgt_evt_counter_t *fn_apply); |
| 95 | |
| 96 | /* |
| 97 | * Emit global counter values. |
| 98 | * This is called during atexit handling. |
| 99 | * |
| 100 | * Caller must be holding the tr2tls_mutex. |
| 101 | */ |
| 102 | void tr2_emit_final_counters(tr2_tgt_evt_counter_t *fn_apply); |
| 103 | |
| 104 | #endif /* TR2_CTR_H */ |