samples/bpf/lathist_user.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
   3  * Copyright (c) 2015 BMW Car IT GmbH
   4  */
   5 #include <stdio.h>
   6 #include <unistd.h>
   7 #include <stdlib.h>
   8 #include <signal.h>
   9 #include <bpf/libbpf.h>
  10 #include <bpf/bpf.h>
  11
  12 #define MAX_ENTRIES     20
  13 #define MAX_CPU         4
  14 #define MAX_STARS       40
  15
  16 struct cpu_hist {
  17         long data[MAX_ENTRIES];
  18         long max;
  19 };
  20
  21 static struct cpu_hist cpu_hist[MAX_CPU];
  22
  23 static void stars(char *str, long val, long max, int width)
  24 {
  25         int i;
  26
  27         for (i = 0; i < (width * val / max) - 1 && i < width - 1; i++)
  28                 str[i] = '*';
  29         if (val > max)
  30                 str[i - 1] = '+';
  31         str[i] = '\0';
  32 }
  33
  34 static void print_hist(void)
  35 {
  36         char starstr[MAX_STARS];
  37         struct cpu_hist *hist;
  38         int i, j;
  39
  40         /* clear screen */
  41         printf("\033[2J");
  42
  43         for (j = 0; j < MAX_CPU; j++) {
  44                 hist = &cpu_hist[j];
  45
  46                 /* ignore CPUs without data (maybe offline?) */
  47                 if (hist->max == 0)
  48                         continue;
  49
  50                 printf("CPU %d\n", j);
  51                 printf("      latency        : count     distribution\n");
  52                 for (i = 1; i <= MAX_ENTRIES; i++) {
  53                         stars(starstr, hist->data[i - 1], hist->max, MAX_STARS);
  54                         printf("%8ld -> %-8ld : %-8ld |%-*s|\n",
  55                                 (1l << i) >> 1, (1l << i) - 1,
  56                                 hist->data[i - 1], MAX_STARS, starstr);
  57                 }
  58         }
  59 }
  60
  61 static void get_data(int fd)
  62 {
  63         long key, value;
  64         int c, i;
  65
  66         for (i = 0; i < MAX_CPU; i++)
  67                 cpu_hist[i].max = 0;
  68
  69         for (c = 0; c < MAX_CPU; c++) {
  70                 for (i = 0; i < MAX_ENTRIES; i++) {
  71                         key = c * MAX_ENTRIES + i;
  72                         bpf_map_lookup_elem(fd, &key, &value);
  73
  74                         cpu_hist[c].data[i] = value;
  75                         if (value > cpu_hist[c].max)
  76                                 cpu_hist[c].max = value;
  77                 }
  78         }
  79 }
  80
  81 int main(int argc, char **argv)
  82 {
  83         struct bpf_link *links[2];
  84         struct bpf_program *prog;
  85         struct bpf_object *obj;
  86         char filename[256];
  87         int map_fd, i = 0;
  88
  89         snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
  90         obj = bpf_object__open_file(filename, NULL);
  91         if (libbpf_get_error(obj)) {
  92                 fprintf(stderr, "ERROR: opening BPF object file failed\n");
  93                 return 0;
  94         }
  95
  96         /* load BPF program */
  97         if (bpf_object__load(obj)) {
  98                 fprintf(stderr, "ERROR: loading BPF object file failed\n");
  99                 goto cleanup;
 100         }
 101
 102         map_fd = bpf_object__find_map_fd_by_name(obj, "my_lat");
 103         if (map_fd < 0) {
 104                 fprintf(stderr, "ERROR: finding a map in obj file failed\n");
 105                 goto cleanup;
 106         }
 107
 108         bpf_object__for_each_program(prog, obj) {
 109                 links[i] = bpf_program__attach(prog);
 110                 if (libbpf_get_error(links[i])) {
 111                         fprintf(stderr, "ERROR: bpf_program__attach failed\n");
 112                         links[i] = NULL;
 113                         goto cleanup;
 114                 }
 115                 i++;
 116         }
 117
 118         while (1) {
 119                 get_data(map_fd);
 120                 print_hist();
 121                 sleep(5);
 122         }
 123
 124 cleanup:
 125         for (i--; i >= 0; i--)
 126                 bpf_link__destroy(links[i]);
 127
 128         bpf_object__close(obj);
 129         return 0;
 130 }