samples/bpf/lathist_user.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
0003  * Copyright (c) 2015 BMW Car IT GmbH
0004  */
0005 #include <stdio.h>
0006 #include <unistd.h>
0007 #include <stdlib.h>
0008 #include <signal.h>
0009 #include <bpf/libbpf.h>
0010 #include <bpf/bpf.h>
0011
0012 #define MAX_ENTRIES 20
0013 #define MAX_CPU     4
0014 #define MAX_STARS   40
0015
0016 struct cpu_hist {
0017     long data[MAX_ENTRIES];
0018     long max;
0019 };
0020
0021 static struct cpu_hist cpu_hist[MAX_CPU];
0022
0023 static void stars(char *str, long val, long max, int width)
0024 {
0025     int i;
0026
0027     for (i = 0; i < (width * val / max) - 1 && i < width - 1; i++)
0028         str[i] = '*';
0029     if (val > max)
0030         str[i - 1] = '+';
0031     str[i] = '\0';
0032 }
0033
0034 static void print_hist(void)
0035 {
0036     char starstr[MAX_STARS];
0037     struct cpu_hist *hist;
0038     int i, j;
0039
0040     /* clear screen */
0041     printf("\033[2J");
0042
0043     for (j = 0; j < MAX_CPU; j++) {
0044         hist = &cpu_hist[j];
0045
0046         /* ignore CPUs without data (maybe offline?) */
0047         if (hist->max == 0)
0048             continue;
0049
0050         printf("CPU %d\n", j);
0051         printf("      latency        : count     distribution\n");
0052         for (i = 1; i <= MAX_ENTRIES; i++) {
0053             stars(starstr, hist->data[i - 1], hist->max, MAX_STARS);
0054             printf("%8ld -> %-8ld : %-8ld |%-*s|\n",
0055                 (1l << i) >> 1, (1l << i) - 1,
0056                 hist->data[i - 1], MAX_STARS, starstr);
0057         }
0058     }
0059 }
0060
0061 static void get_data(int fd)
0062 {
0063     long key, value;
0064     int c, i;
0065
0066     for (i = 0; i < MAX_CPU; i++)
0067         cpu_hist[i].max = 0;
0068
0069     for (c = 0; c < MAX_CPU; c++) {
0070         for (i = 0; i < MAX_ENTRIES; i++) {
0071             key = c * MAX_ENTRIES + i;
0072             bpf_map_lookup_elem(fd, &key, &value);
0073
0074             cpu_hist[c].data[i] = value;
0075             if (value > cpu_hist[c].max)
0076                 cpu_hist[c].max = value;
0077         }
0078     }
0079 }
0080
0081 int main(int argc, char **argv)
0082 {
0083     struct bpf_link *links[2];
0084     struct bpf_program *prog;
0085     struct bpf_object *obj;
0086     char filename[256];
0087     int map_fd, i = 0;
0088
0089     snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
0090     obj = bpf_object__open_file(filename, NULL);
0091     if (libbpf_get_error(obj)) {
0092         fprintf(stderr, "ERROR: opening BPF object file failed\n");
0093         return 0;
0094     }
0095
0096     /* load BPF program */
0097     if (bpf_object__load(obj)) {
0098         fprintf(stderr, "ERROR: loading BPF object file failed\n");
0099         goto cleanup;
0100     }
0101
0102     map_fd = bpf_object__find_map_fd_by_name(obj, "my_lat");
0103     if (map_fd < 0) {
0104         fprintf(stderr, "ERROR: finding a map in obj file failed\n");
0105         goto cleanup;
0106     }
0107
0108     bpf_object__for_each_program(prog, obj) {
0109         links[i] = bpf_program__attach(prog);
0110         if (libbpf_get_error(links[i])) {
0111             fprintf(stderr, "ERROR: bpf_program__attach failed\n");
0112             links[i] = NULL;
0113             goto cleanup;
0114         }
0115         i++;
0116     }
0117
0118     while (1) {
0119         get_data(map_fd);
0120         print_hist();
0121         sleep(5);
0122     }
0123
0124 cleanup:
0125     for (i--; i >= 0; i--)
0126         bpf_link__destroy(links[i]);
0127
0128     bpf_object__close(obj);
0129     return 0;
0130 }