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Date:   Wed, 6 Dec 2017 21:51:36 +0100
From:   Philippe Ombredanne <pombredanne@...b.com>
To:     Song Liu <songliubraving@...com>
Cc:     peterz@...radead.org, Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>, daniel@...earbox.net,
        kernel-team@...com
Subject: Re: [PATCH v4 6/6] bpf: add new test test_many_kprobe

Song,

On Tue, Dec 5, 2017 at 2:27 AM, Song Liu <songliubraving@...com> wrote:
> The test compares old text based kprobe API with perf_kprobe.
>
> Here is a sample output of this test:
>
> Creating 1000 kprobes with text-based API takes 6.979683 seconds
> Cleaning 1000 kprobes with text-based API takes 84.897687 seconds
> Creating 1000 kprobes with perf_kprobe (function name) takes 5.077558 seconds
> Cleaning 1000 kprobes with perf_kprobe (function name) takes 81.241354 seconds
> Creating 1000 kprobes with perf_kprobe (function addr) takes 5.218255 seconds
> Cleaning 1000 kprobes with perf_kprobe (function addr) takes 80.010731 seconds
>
> Signed-off-by: Song Liu <songliubraving@...com>
> Reviewed-by: Josef Bacik <jbacik@...com>
> Reviewed-by: Philippe Ombredanne <pombredanne@...b.com>
> ---
>  samples/bpf/Makefile                |   3 +
>  samples/bpf/bpf_load.c              |   5 +-
>  samples/bpf/bpf_load.h              |   4 +
>  samples/bpf/test_many_kprobe_user.c | 186 ++++++++++++++++++++++++++++++++++++
>  4 files changed, 195 insertions(+), 3 deletions(-)
>  create mode 100644 samples/bpf/test_many_kprobe_user.c
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 9b4a66e..ec92f35 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -42,6 +42,7 @@ hostprogs-y += xdp_redirect
>  hostprogs-y += xdp_redirect_map
>  hostprogs-y += xdp_monitor
>  hostprogs-y += syscall_tp
> +hostprogs-y += test_many_kprobe
>
>  # Libbpf dependencies
>  LIBBPF := ../../tools/lib/bpf/bpf.o
> @@ -87,6 +88,7 @@ xdp_redirect-objs := bpf_load.o $(LIBBPF) xdp_redirect_user.o
>  xdp_redirect_map-objs := bpf_load.o $(LIBBPF) xdp_redirect_map_user.o
>  xdp_monitor-objs := bpf_load.o $(LIBBPF) xdp_monitor_user.o
>  syscall_tp-objs := bpf_load.o $(LIBBPF) syscall_tp_user.o
> +test_many_kprobe-objs := bpf_load.o $(LIBBPF) test_many_kprobe_user.o
>
>  # Tell kbuild to always build the programs
>  always := $(hostprogs-y)
> @@ -172,6 +174,7 @@ HOSTLOADLIBES_xdp_redirect += -lelf
>  HOSTLOADLIBES_xdp_redirect_map += -lelf
>  HOSTLOADLIBES_xdp_monitor += -lelf
>  HOSTLOADLIBES_syscall_tp += -lelf
> +HOSTLOADLIBES_test_many_kprobe += -lelf
>
>  # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
>  #  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
> diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
> index b11c1c1..ffe2c49d 100644
> --- a/samples/bpf/bpf_load.c
> +++ b/samples/bpf/bpf_load.c
> @@ -664,9 +664,8 @@ void read_trace_pipe(void)
>         }
>  }
>
> -#define MAX_SYMS 300000
> -static struct ksym syms[MAX_SYMS];
> -static int sym_cnt;
> +struct ksym syms[MAX_SYMS];
> +int sym_cnt;
>
>  static int ksym_cmp(const void *p1, const void *p2)
>  {
> diff --git a/samples/bpf/bpf_load.h b/samples/bpf/bpf_load.h
> index 95d6be5..6c9d584 100644
> --- a/samples/bpf/bpf_load.h
> +++ b/samples/bpf/bpf_load.h
> @@ -69,6 +69,10 @@ static inline __u64 ptr_to_u64(const void *ptr)
>         return (__u64) (unsigned long) ptr;
>  }
>
> +#define MAX_SYMS 300000
> +extern struct ksym syms[MAX_SYMS];
> +extern int sym_cnt;
> +
>  int load_kallsyms(void);
>  struct ksym *ksym_search(long key);
>  int set_link_xdp_fd(int ifindex, int fd, __u32 flags);
> diff --git a/samples/bpf/test_many_kprobe_user.c b/samples/bpf/test_many_kprobe_user.c
> new file mode 100644
> index 0000000..6c111cf
> --- /dev/null
> +++ b/samples/bpf/test_many_kprobe_user.c
> @@ -0,0 +1,186 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2017 Facebook
> +
> +#define _GNU_SOURCE
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include <string.h>
> +#include <libelf.h>
> +#include <gelf.h>
> +#include <linux/version.h>
> +#include <errno.h>
> +#include <stdbool.h>
> +#include <time.h>
> +#include "libbpf.h"
> +#include "bpf_load.h"
> +#include "perf-sys.h"
> +
> +#define MAX_KPROBES 1000
> +
> +#define DEBUGFS "/sys/kernel/debug/tracing/"
> +
> +int kprobes[MAX_KPROBES] = {0};
> +int kprobe_count;
> +int perf_event_fds[MAX_KPROBES];
> +const char license[] = "GPL";
> +
> +static __u64 time_get_ns(void)
> +{
> +       struct timespec ts;
> +
> +       clock_gettime(CLOCK_MONOTONIC, &ts);
> +       return ts.tv_sec * 1000000000ull + ts.tv_nsec;
> +}
> +
> +static int kprobe_api(char *func, void *addr, bool use_new_api)
> +{
> +       int efd;
> +       struct perf_event_attr attr = {};
> +       char buf[256];
> +       int err, id;
> +
> +       attr.sample_type = PERF_SAMPLE_RAW;
> +       attr.sample_period = 1;
> +       attr.wakeup_events = 1;
> +
> +       if (use_new_api) {
> +               attr.type = perf_kprobe_type;
> +               if (func) {
> +                       attr.kprobe_func = ptr_to_u64(func);
> +                       attr.probe_offset = 0;
> +               } else {
> +                       attr.kprobe_func = 0;
> +                       attr.kprobe_addr = ptr_to_u64(addr);
> +               }
> +       } else {
> +               attr.type = PERF_TYPE_TRACEPOINT;
> +               snprintf(buf, sizeof(buf),
> +                        "echo 'p:%s %s' >> /sys/kernel/debug/tracing/kprobe_events",
> +                        func, func);
> +               err = system(buf);
> +               if (err < 0) {
> +                       printf("failed to create kprobe '%s' error '%s'\n",
> +                              func, strerror(errno));
> +                       return -1;
> +               }
> +
> +               strcpy(buf, DEBUGFS);
> +               strcat(buf, "events/kprobes/");
> +               strcat(buf, func);
> +               strcat(buf, "/id");
> +               efd = open(buf, O_RDONLY, 0);
> +               if (efd < 0) {
> +                       printf("failed to open event %s\n", func);
> +                       return -1;
> +               }
> +
> +               err = read(efd, buf, sizeof(buf));
> +               if (err < 0 || err >= sizeof(buf)) {
> +                       printf("read from '%s' failed '%s'\n", func,
> +                              strerror(errno));
> +                       return -1;
> +               }
> +
> +               close(efd);
> +               buf[err] = 0;
> +               id = atoi(buf);
> +               attr.config = id;
> +       }
> +
> +       attr.size = sizeof(attr);
> +       efd = sys_perf_event_open(&attr, -1/*pid*/, 0/*cpu*/,
> +                                 -1/*group_fd*/, 0);
> +
> +       return efd;
> +}
> +
> +static int select_kprobes(void)
> +{
> +       int fd;
> +       int i;
> +
> +       load_kallsyms();
> +
> +       kprobe_count = 0;
> +       for (i = 0; i < sym_cnt; i++) {
> +               if (strstr(syms[i].name, "."))
> +                       continue;
> +               fd = kprobe_api(syms[i].name, NULL, false);
> +               if (fd < 0)
> +                       continue;
> +               close(fd);
> +               kprobes[kprobe_count] = i;
> +               if (++kprobe_count >= MAX_KPROBES)
> +                       break;
> +       }
> +
> +       return 0;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +       int i;
> +       __u64 start_time;
> +
> +       select_kprobes();
> +
> +       /* clean all trace_kprobe */
> +       i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events");
> +
> +       /* test text based API */
> +       start_time = time_get_ns();
> +       for (i = 0; i < kprobe_count; i++)
> +               perf_event_fds[i] = kprobe_api(syms[kprobes[i]].name,
> +                                              NULL, false);
> +       printf("Creating %d kprobes with text-based API takes %f seconds\n",
> +              kprobe_count, (time_get_ns() - start_time) / 1000000000.0);
> +
> +       start_time = time_get_ns();
> +       for (i = 0; i < kprobe_count; i++)
> +               if (perf_event_fds[i] > 0)
> +                       close(perf_event_fds[i]);
> +       i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events");
> +       printf("Cleaning %d kprobes with text-based API takes %f seconds\n",
> +              kprobe_count, (time_get_ns() - start_time) / 1000000000.0);
> +
> +       get_perf_kprobe_type_id();
> +       if (perf_kprobe_type == -1) {
> +               printf("The kernel does support perf_kprobe.\n"
> +                      "Existing...\n");
> +               return 0;
> +       }
> +
> +       /* test perf_kprobe API, with function names */
> +       start_time = time_get_ns();
> +       for (i = 0; i < kprobe_count; i++)
> +               perf_event_fds[i] = kprobe_api(syms[kprobes[i]].name,
> +                                              NULL, true);
> +       printf("Creating %d kprobes with perf_kprobe (function name) takes %f seconds\n",
> +              kprobe_count, (time_get_ns() - start_time) / 1000000000.0);
> +
> +       start_time = time_get_ns();
> +       for (i = 0; i < kprobe_count; i++)
> +               if (perf_event_fds[i] > 0)
> +                       close(perf_event_fds[i]);
> +       printf("Cleaning %d kprobes with perf_kprobe (function name) takes %f seconds\n",
> +              kprobe_count, (time_get_ns() - start_time) / 1000000000.0);
> +
> +       /* test perf_kprobe API, with function address */
> +       start_time = time_get_ns();
> +       for (i = 0; i < kprobe_count; i++)
> +               perf_event_fds[i] = kprobe_api(
> +                       NULL, (void *)(syms[kprobes[i]].addr), true);
> +       printf("Creating %d kprobes with perf_kprobe (function addr) takes %f seconds\n",
> +              kprobe_count, (time_get_ns() - start_time) / 1000000000.0);
> +
> +       start_time = time_get_ns();
> +       for (i = 0; i < kprobe_count; i++)
> +               if (perf_event_fds[i] > 0)
> +                       close(perf_event_fds[i]);
> +       printf("Cleaning %d kprobes with perf_kprobe (function addr) takes %f seconds\n",
> +              kprobe_count, (time_get_ns() - start_time) / 1000000000.0);
> +       return 0;
> +}
> --
> 2.9.5
>

Ack, and thank you very much for the usage of the SDPX license id that
I reviewed.

-- 
Cordially
Philippe Ombredanne

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