samples/bpf/test_overhead_user.c

// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2016 Facebook
 */
#define _GNU_SOURCE
#include <sched.h>
#include <errno.h>
#include <stdio.h>
#include <sys/types.h>
#include <asm/unistd.h>
#include <fcntl.h>
#include <unistd.h>
#include <assert.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <signal.h>
#include <linux/bpf.h>
#include <string.h>
#include <time.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>

#define MAX_CNT 1000000

static struct bpf_link *links[2];
static struct bpf_object *obj;
static int cnt;

static __u64 time_get_ns(void)
{
	struct timespec ts;

	clock_gettime(CLOCK_MONOTONIC, &ts);
	return ts.tv_sec * 1000000000ull + ts.tv_nsec;
}

static void test_task_rename(int cpu)
{
	__u64 start_time;
	char buf[] = "test\n";
	int i, fd;

	fd = open("/proc/self/comm", O_WRONLY|O_TRUNC);
	if (fd < 0) {
		printf("couldn't open /proc\n");
		exit(1);
	}
	start_time = time_get_ns();
	for (i = 0; i < MAX_CNT; i++) {
		if (write(fd, buf, sizeof(buf)) < 0) {
			printf("task rename failed: %s\n", strerror(errno));
			close(fd);
			return;
		}
	}
	printf("task_rename:%d: %lld events per sec\n",
	       cpu, MAX_CNT * 1000000000ll / (time_get_ns() - start_time));
	close(fd);
}

static void test_urandom_read(int cpu)
{
	__u64 start_time;
	char buf[4];
	int i, fd;

	fd = open("/dev/urandom", O_RDONLY);
	if (fd < 0) {
		printf("couldn't open /dev/urandom\n");
		exit(1);
	}
	start_time = time_get_ns();
	for (i = 0; i < MAX_CNT; i++) {
		if (read(fd, buf, sizeof(buf)) < 0) {
			printf("failed to read from /dev/urandom: %s\n", strerror(errno));
			close(fd);
			return;
		}
	}
	printf("urandom_read:%d: %lld events per sec\n",
	       cpu, MAX_CNT * 1000000000ll / (time_get_ns() - start_time));
	close(fd);
}

static void loop(int cpu, int flags)
{
	cpu_set_t cpuset;

	CPU_ZERO(&cpuset);
	CPU_SET(cpu, &cpuset);
	sched_setaffinity(0, sizeof(cpuset), &cpuset);

	if (flags & 1)
		test_task_rename(cpu);
	if (flags & 2)
		test_urandom_read(cpu);
}

static void run_perf_test(int tasks, int flags)
{
	pid_t pid[tasks];
	int i;

	for (i = 0; i < tasks; i++) {
		pid[i] = fork();
		if (pid[i] == 0) {
			loop(i, flags);
			exit(0);
		} else if (pid[i] == -1) {
			printf("couldn't spawn #%d process\n", i);
			exit(1);
		}
	}
	for (i = 0; i < tasks; i++) {
		int status;

		assert(waitpid(pid[i], &status, 0) == pid[i]);
		assert(status == 0);
	}
}

static int load_progs(char *filename)
{
	struct bpf_program *prog;
	int err = 0;

	obj = bpf_object__open_file(filename, NULL);
	err = libbpf_get_error(obj);
	if (err < 0) {
		fprintf(stderr, "ERROR: opening BPF object file failed\n");
		return err;
	}

	/* load BPF program */
	err = bpf_object__load(obj);
	if (err < 0) {
		fprintf(stderr, "ERROR: loading BPF object file failed\n");
		return err;
	}

	bpf_object__for_each_program(prog, obj) {
		links[cnt] = bpf_program__attach(prog);
		err = libbpf_get_error(links[cnt]);
		if (err < 0) {
			fprintf(stderr, "ERROR: bpf_program__attach failed\n");
			links[cnt] = NULL;
			return err;
		}
		cnt++;
	}

	return err;
}

static void unload_progs(void)
{
	while (cnt)
		bpf_link__destroy(links[--cnt]);

	bpf_object__close(obj);
}

int main(int argc, char **argv)
{
	int num_cpu = sysconf(_SC_NPROCESSORS_ONLN);
	int test_flags = ~0;
	char filename[256];
	int err = 0;


	if (argc > 1)
		test_flags = atoi(argv[1]) ? : test_flags;
	if (argc > 2)
		num_cpu = atoi(argv[2]) ? : num_cpu;

	if (test_flags & 0x3) {
		printf("BASE\n");
		run_perf_test(num_cpu, test_flags);
	}

	if (test_flags & 0xC) {
		snprintf(filename, sizeof(filename),
			 "%s_kprobe_kern.o", argv[0]);

		printf("w/KPROBE\n");
		err = load_progs(filename);
		if (!err)
			run_perf_test(num_cpu, test_flags >> 2);

		unload_progs();
	}

	if (test_flags & 0x30) {
		snprintf(filename, sizeof(filename),
			 "%s_tp_kern.o", argv[0]);
		printf("w/TRACEPOINT\n");
		err = load_progs(filename);
		if (!err)
			run_perf_test(num_cpu, test_flags >> 4);

		unload_progs();
	}

	if (test_flags & 0xC0) {
		snprintf(filename, sizeof(filename),
			 "%s_raw_tp_kern.o", argv[0]);
		printf("w/RAW_TRACEPOINT\n");
		err = load_progs(filename);
		if (!err)
			run_perf_test(num_cpu, test_flags >> 6);

		unload_progs();
	}

	return err;
}