tools/lib/perf/Documentation/examples/sampling.c

   1 #include <linux/perf_event.h>
   2 #include <perf/evlist.h>
   3 #include <perf/evsel.h>
   4 #include <perf/cpumap.h>
   5 #include <perf/threadmap.h>
   6 #include <perf/mmap.h>
   7 #include <perf/core.h>
   8 #include <perf/event.h>
   9 #include <stdio.h>
  10 #include <unistd.h>
  11
  12 static int libperf_print(enum libperf_print_level level,
  13                          const char *fmt, va_list ap)
  14 {
  15         return vfprintf(stderr, fmt, ap);
  16 }
  17
  18 union u64_swap {
  19         __u64 val64;
  20         __u32 val32[2];
  21 };
  22
  23 int main(int argc, char **argv)
  24 {
  25         struct perf_evlist *evlist;
  26         struct perf_evsel *evsel;
  27         struct perf_mmap *map;
  28         struct perf_cpu_map *cpus;
  29         struct perf_event_attr attr = {
  30                 .type        = PERF_TYPE_HARDWARE,
  31                 .config      = PERF_COUNT_HW_CPU_CYCLES,
  32                 .disabled    = 1,
  33                 .freq        = 1,
  34                 .sample_freq = 10,
  35                 .sample_type = PERF_SAMPLE_IP|PERF_SAMPLE_TID|PERF_SAMPLE_CPU|PERF_SAMPLE_PERIOD,
  36         };
  37         int err = -1;
  38         union perf_event *event;
  39
  40         libperf_init(libperf_print);
  41
  42         cpus = perf_cpu_map__new(NULL);
  43         if (!cpus) {
  44                 fprintf(stderr, "failed to create cpus\n");
  45                 return -1;
  46         }
  47
  48         evlist = perf_evlist__new();
  49         if (!evlist) {
  50                 fprintf(stderr, "failed to create evlist\n");
  51                 goto out_cpus;
  52         }
  53
  54         evsel = perf_evsel__new(&attr);
  55         if (!evsel) {
  56                 fprintf(stderr, "failed to create cycles\n");
  57                 goto out_cpus;
  58         }
  59
  60         perf_evlist__add(evlist, evsel);
  61
  62         perf_evlist__set_maps(evlist, cpus, NULL);
  63
  64         err = perf_evlist__open(evlist);
  65         if (err) {
  66                 fprintf(stderr, "failed to open evlist\n");
  67                 goto out_evlist;
  68         }
  69
  70         err = perf_evlist__mmap(evlist, 4);
  71         if (err) {
  72                 fprintf(stderr, "failed to mmap evlist\n");
  73                 goto out_evlist;
  74         }
  75
  76         perf_evlist__enable(evlist);
  77         sleep(3);
  78         perf_evlist__disable(evlist);
  79
  80         perf_evlist__for_each_mmap(evlist, map, false) {
  81                 if (perf_mmap__read_init(map) < 0)
  82                         continue;
  83
  84                 while ((event = perf_mmap__read_event(map)) != NULL) {
  85                         int cpu, pid, tid;
  86                         __u64 ip, period, *array;
  87                         union u64_swap u;
  88
  89                         array = event->sample.array;
  90
  91                         ip = *array;
  92                         array++;
  93
  94                         u.val64 = *array;
  95                         pid = u.val32[0];
  96                         tid = u.val32[1];
  97                         array++;
  98
  99                         u.val64 = *array;
 100                         cpu = u.val32[0];
 101                         array++;
 102
 103                         period = *array;
 104
 105                         fprintf(stdout, "cpu %3d, pid %6d, tid %6d, ip %20llx, period %20llu\n",
 106                                 cpu, pid, tid, ip, period);
 107
 108                         perf_mmap__consume(map);
 109                 }
 110
 111                 perf_mmap__read_done(map);
 112         }
 113
 114 out_evlist:
 115         perf_evlist__delete(evlist);
 116 out_cpus:
 117         perf_cpu_map__put(cpus);
 118         return err;
 119 }