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Message-ID: <20200123232040.dqsswmoltc3rlqhm@kafai-mbp.dhcp.thefacebook.com>
Date: Thu, 23 Jan 2020 23:20:44 +0000
From: Martin Lau <kafai@...com>
To: Daniel Xu <dxu@...uu.xyz>
CC: "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
"ast@...nel.org" <ast@...nel.org>,
"daniel@...earbox.net" <daniel@...earbox.net>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
Andrii Nakryiko <andriin@...com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Kernel Team <Kernel-team@...com>,
"peterz@...radead.org" <peterz@...radead.org>,
"mingo@...hat.com" <mingo@...hat.com>,
"acme@...nel.org" <acme@...nel.org>
Subject: Re: [PATCH v3 bpf-next 3/3] selftests/bpf: add
bpf_perf_prog_read_branches() selftest
On Thu, Jan 23, 2020 at 01:23:12PM -0800, Daniel Xu wrote:
> Signed-off-by: Daniel Xu <dxu@...uu.xyz>
Please put some details to avoid empty commit message.
Same for patch 2.
> ---
> .../selftests/bpf/prog_tests/perf_branches.c | 106 ++++++++++++++++++
> .../selftests/bpf/progs/test_perf_branches.c | 39 +++++++
> 2 files changed, 145 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_branches.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_perf_branches.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/perf_branches.c b/tools/testing/selftests/bpf/prog_tests/perf_branches.c
> new file mode 100644
> index 000000000000..f8d7356a6507
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/perf_branches.c
> @@ -0,0 +1,106 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <pthread.h>
> +#include <sched.h>
> +#include <sys/socket.h>
> +#include <test_progs.h>
> +#include "bpf/libbpf_internal.h"
> +
> +static void on_sample(void *ctx, int cpu, void *data, __u32 size)
> +{
> + int pbe_size = sizeof(struct perf_branch_entry);
> + int ret = *(int *)data, duration = 0;
> +
> + // It's hard to validate the contents of the branch entries b/c it
> + // would require some kind of disassembler and also encoding the
> + // valid jump instructions for supported architectures. So just check
> + // the easy stuff for now.
/* ... */ comment style
> + CHECK(ret < 0, "read_branches", "err %d\n", ret);
> + CHECK(ret % pbe_size != 0, "read_branches",
> + "bytes written=%d not multiple of struct size=%d\n",
> + ret, pbe_size);
> +
> + *(int *)ctx = 1;
> +}
> +
> +void test_perf_branches(void)
> +{
> + int err, prog_fd, i, pfd = -1, duration = 0, ok = 0;
> + const char *file = "./test_perf_branches.o";
> + const char *prog_name = "perf_event";
> + struct perf_buffer_opts pb_opts = {};
> + struct perf_event_attr attr = {};
> + struct bpf_map *perf_buf_map;
> + struct bpf_program *prog;
> + struct bpf_object *obj;
> + struct perf_buffer *pb;
> + struct bpf_link *link;
> + volatile int j = 0;
> + cpu_set_t cpu_set;
> +
> + /* load program */
> + err = bpf_prog_load(file, BPF_PROG_TYPE_PERF_EVENT, &obj, &prog_fd);
> + if (CHECK(err, "obj_load", "err %d errno %d\n", err, errno)) {
> + obj = NULL;
> + goto out_close;
> + }
> +
> + prog = bpf_object__find_program_by_title(obj, prog_name);
> + if (CHECK(!prog, "find_probe", "prog '%s' not found\n", prog_name))
> + goto out_close;
> +
> + /* load map */
> + perf_buf_map = bpf_object__find_map_by_name(obj, "perf_buf_map");
> + if (CHECK(!perf_buf_map, "find_perf_buf_map", "not found\n"))
> + goto out_close;
Using skel may be able to cut some lines.
> +
> + /* create perf event */
> + attr.size = sizeof(attr);
> + attr.type = PERF_TYPE_HARDWARE;
> + attr.config = PERF_COUNT_HW_CPU_CYCLES;
> + attr.freq = 1;
> + attr.sample_freq = 4000;
> + attr.sample_type = PERF_SAMPLE_BRANCH_STACK;
> + attr.branch_sample_type = PERF_SAMPLE_BRANCH_USER | PERF_SAMPLE_BRANCH_ANY;
> + pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
> + if (CHECK(pfd < 0, "perf_event_open", "err %d\n", pfd))
> + goto out_close;
> +
> + /* attach perf_event */
> + link = bpf_program__attach_perf_event(prog, pfd);
> + if (CHECK(IS_ERR(link), "attach_perf_event", "err %ld\n", PTR_ERR(link)))
> + goto out_close_perf;
> +
> + /* set up perf buffer */
> + pb_opts.sample_cb = on_sample;
> + pb_opts.ctx = &ok;
> + pb = perf_buffer__new(bpf_map__fd(perf_buf_map), 1, &pb_opts);
> + if (CHECK(IS_ERR(pb), "perf_buf__new", "err %ld\n", PTR_ERR(pb)))
> + goto out_detach;
> +
> + /* generate some branches on cpu 0 */
> + CPU_ZERO(&cpu_set);
> + CPU_SET(0, &cpu_set);
> + err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set), &cpu_set);
> + if (err && CHECK(err, "set_affinity", "cpu #0, err %d\n", err))
'err &&' seems unnecessary.
> + goto out_free_pb;
> + for (i = 0; i < 1000000; ++i)
May be some comments on 1000000?
> + ++j;
> +
> + /* read perf buffer */
> + err = perf_buffer__poll(pb, 500);
> + if (CHECK(err < 0, "perf_buffer__poll", "err %d\n", err))
> + goto out_free_pb;
> +
> + if (CHECK(!ok, "ok", "not ok\n"))
> + goto out_free_pb;
> +
> +out_free_pb:
> + perf_buffer__free(pb);
> +out_detach:
> + bpf_link__destroy(link);
> +out_close_perf:
> + close(pfd);
> +out_close:
> + bpf_object__close(obj);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_perf_branches.c b/tools/testing/selftests/bpf/progs/test_perf_branches.c
> new file mode 100644
> index 000000000000..d818079c7778
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_perf_branches.c
> @@ -0,0 +1,39 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2019 Facebook
> +
> +#include <linux/ptrace.h>
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +#include "bpf_trace_helpers.h"
> +
> +struct {
> + __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
> + __uint(key_size, sizeof(int));
> + __uint(value_size, sizeof(int));
> +} perf_buf_map SEC(".maps");
> +
> +struct fake_perf_branch_entry {
> + __u64 _a;
> + __u64 _b;
> + __u64 _c;
> +};
> +
> +SEC("perf_event")
> +int perf_branches(void *ctx)
> +{
> + int ret;
> + struct fake_perf_branch_entry entries[4];
Try to keep the reverse xmas tree.
> +
> + ret = bpf_perf_prog_read_branches(ctx,
> + entries,
> + sizeof(entries));
> + /* ignore spurious events */
> + if (!ret)
Check for -ve also?
> + return 1;
> +
> + bpf_perf_event_output(ctx, &perf_buf_map, BPF_F_CURRENT_CPU,
> + &ret, sizeof(ret));
> + return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.21.1
>
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