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Commit e3edfdec authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

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: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3c9b1644

samples/bpf/Makefile

+5 −0
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ hostprogs-y += lathist 
hostprogs-y += offwaketime

hostprogs-y += spintest

hostprogs-y += map_perf_test

hostprogs-y += test_overhead



test_verifier-objs := test_verifier.o libbpf.o

test_maps-objs := test_maps.o libbpf.o
@@ -38,6 +39,7 @@ lathist-objs := bpf_load.o libbpf.o lathist_user.o 
offwaketime-objs := bpf_load.o libbpf.o offwaketime_user.o

spintest-objs := bpf_load.o libbpf.o spintest_user.o

map_perf_test-objs := bpf_load.o libbpf.o map_perf_test_user.o

test_overhead-objs := bpf_load.o libbpf.o test_overhead_user.o



# Tell kbuild to always build the programs

always := $(hostprogs-y)
@@ -56,6 +58,8 @@ always += lathist_kern.o 
always += offwaketime_kern.o

always += spintest_kern.o

always += map_perf_test_kern.o

always += test_overhead_tp_kern.o

always += test_overhead_kprobe_kern.o



HOSTCFLAGS += -I$(objtree)/usr/include
@@ -75,6 +79,7 @@ HOSTLOADLIBES_lathist += -lelf 
HOSTLOADLIBES_offwaketime += -lelf

HOSTLOADLIBES_spintest += -lelf

HOSTLOADLIBES_map_perf_test += -lelf -lrt

HOSTLOADLIBES_test_overhead += -lelf -lrt



# point this to your LLVM backend with bpf support

LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc

samples/bpf/test_overhead_kprobe_kern.c

0 → 100644
+41 −0
Original line number Diff line number Diff line 
/* 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.

 */

#include <linux/version.h>

#include <linux/ptrace.h>

#include <uapi/linux/bpf.h>

#include "bpf_helpers.h"



#define _(P) ({typeof(P) val = 0; bpf_probe_read(&val, sizeof(val), &P); val;})



SEC("kprobe/__set_task_comm")

int prog(struct pt_regs *ctx)

{

	struct signal_struct *signal;

	struct task_struct *tsk;

	char oldcomm[16] = {};

	char newcomm[16] = {};

	u16 oom_score_adj;

	u32 pid;



	tsk = (void *)PT_REGS_PARM1(ctx);



	pid = _(tsk->pid);

	bpf_probe_read(oldcomm, sizeof(oldcomm), &tsk->comm);

	bpf_probe_read(newcomm, sizeof(newcomm), (void *)PT_REGS_PARM2(ctx));

	signal = _(tsk->signal);

	oom_score_adj = _(signal->oom_score_adj);

	return 0;

}



SEC("kprobe/urandom_read")

int prog2(struct pt_regs *ctx)

{

	return 0;

}



char _license[] SEC("license") = "GPL";

u32 _version SEC("version") = LINUX_VERSION_CODE;

samples/bpf/test_overhead_tp_kern.c

0 → 100644
+36 −0
Original line number Diff line number Diff line 
/* 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.

 */

#include <uapi/linux/bpf.h>

#include "bpf_helpers.h"



/* from /sys/kernel/debug/tracing/events/task/task_rename/format */

struct task_rename {

	__u64 pad;

	__u32 pid;

	char oldcomm[16];

	char newcomm[16];

	__u16 oom_score_adj;

};

SEC("tracepoint/task/task_rename")

int prog(struct task_rename *ctx)

{

	return 0;

}



/* from /sys/kernel/debug/tracing/events/random/urandom_read/format */

struct urandom_read {

	__u64 pad;

	int got_bits;

	int pool_left;

	int input_left;

};

SEC("tracepoint/random/urandom_read")

int prog2(struct urandom_read *ctx)

{

	return 0;

}

char _license[] SEC("license") = "GPL";

samples/bpf/test_overhead_user.c

0 → 100644
+162 −0
Original line number Diff line number Diff line 
/* 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;

}