samples/bpf: add tracepoint vs kprobe performance tests
the first microbenchmark does
fd=open("/proc/self/comm");
for() {
write(fd, "test");
}
and on 4 cpus in parallel:
writes per sec
base (no tracepoints, no kprobes) 930k
with kprobe at __set_task_comm() 420k
with tracepoint at task:task_rename 730k
For kprobe + full bpf program manully fetches oldcomm, newcomm via bpf_probe_read.
For tracepint bpf program does nothing, since arguments are copied by tracepoint.
2nd microbenchmark does:
fd=open("/dev/urandom");
for() {
read(fd, buf);
}
and on 4 cpus in parallel:
reads per sec
base (no tracepoints, no kprobes) 300k
with kprobe at urandom_read() 279k
with tracepoint at random:urandom_read 290k
bpf progs attached to kprobe and tracepoint are noop.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/samples/bpf/test_overhead_user.c b/samples/bpf/test_overhead_user.c
new file mode 100644
index 0000000..d291167f
--- /dev/null
+++ b/samples/bpf/test_overhead_user.c
@@ -0,0 +1,162 @@
+/* Copyright (c) 2016 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#define _GNU_SOURCE
+#include <sched.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 <sys/resource.h>
+#include "libbpf.h"
+#include "bpf_load.h"
+
+#define MAX_CNT 1000000
+
+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++)
+ write(fd, buf, sizeof(buf));
+ 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++)
+ read(fd, buf, sizeof(buf));
+ 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 void unload_progs(void)
+{
+ close(prog_fd[0]);
+ close(prog_fd[1]);
+ close(event_fd[0]);
+ close(event_fd[1]);
+}
+
+int main(int argc, char **argv)
+{
+ struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
+ char filename[256];
+ int num_cpu = 8;
+ int test_flags = ~0;
+
+ setrlimit(RLIMIT_MEMLOCK, &r);
+
+ 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]);
+ if (load_bpf_file(filename)) {
+ printf("%s", bpf_log_buf);
+ return 1;
+ }
+ printf("w/KPROBE\n");
+ run_perf_test(num_cpu, test_flags >> 2);
+ unload_progs();
+ }
+
+ if (test_flags & 0x30) {
+ snprintf(filename, sizeof(filename),
+ "%s_tp_kern.o", argv[0]);
+ if (load_bpf_file(filename)) {
+ printf("%s", bpf_log_buf);
+ return 1;
+ }
+ printf("w/TRACEPOINT\n");
+ run_perf_test(num_cpu, test_flags >> 4);
+ unload_progs();
+ }
+
+ return 0;
+}