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Date: Wed, 15 Jul 2020 23:04:58 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Song Liu <songliubraving@...com>
Cc: open list <linux-kernel@...r.kernel.org>,
bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Kernel Team <kernel-team@...com>,
john fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...omium.org>,
Jesper Dangaard Brouer <brouer@...hat.com>,
Peter Ziljstra <peterz@...radead.org>
Subject: Re: [PATCH v2 bpf-next 2/2] selftests/bpf: add callchain_stackid
On Tue, Jul 14, 2020 at 11:09 PM Song Liu <songliubraving@...com> wrote:
>
> This tests new helper function bpf_get_stackid_pe and bpf_get_stack_pe.
> These two helpers have different implementation for perf_event with PEB
> entries.
>
> Signed-off-by: Song Liu <songliubraving@...com>
> ---
> .../bpf/prog_tests/perf_event_stackmap.c | 120 ++++++++++++++++++
> .../selftests/bpf/progs/perf_event_stackmap.c | 64 ++++++++++
> 2 files changed, 184 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/perf_event_stackmap.c
> create mode 100644 tools/testing/selftests/bpf/progs/perf_event_stackmap.c
>
Just few simplification suggestions, but overall looks good, so please add:
Acked-by: Andrii Nakryiko <andriin@...com>
[...]
> +
> +void test_perf_event_stackmap(void)
> +{
> + struct perf_event_attr attr = {
> + /* .type = PERF_TYPE_SOFTWARE, */
> + .type = PERF_TYPE_HARDWARE,
> + .config = PERF_COUNT_HW_CPU_CYCLES,
> + .precise_ip = 2,
> + .sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_BRANCH_STACK |
> + PERF_SAMPLE_CALLCHAIN,
> + .branch_sample_type = PERF_SAMPLE_BRANCH_USER |
> + PERF_SAMPLE_BRANCH_NO_FLAGS |
> + PERF_SAMPLE_BRANCH_NO_CYCLES |
> + PERF_SAMPLE_BRANCH_CALL_STACK,
> + .sample_period = 5000,
> + .size = sizeof(struct perf_event_attr),
> + };
> + struct perf_event_stackmap *skel;
> + __u32 duration = 0;
> + cpu_set_t cpu_set;
> + int pmu_fd, err;
> +
> + skel = perf_event_stackmap__open();
> +
> + if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
> + return;
> +
> + /* override program type */
> + bpf_program__set_perf_event(skel->progs.oncpu);
this should be unnecessary, didn't libbpf detect the type correctly
from SEC? If not, let's fix that.
> +
> + err = perf_event_stackmap__load(skel);
> + if (CHECK(err, "skel_load", "skeleton load failed: %d\n", err))
> + goto cleanup;
> +
> + CPU_ZERO(&cpu_set);
> + CPU_SET(0, &cpu_set);
> + err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set), &cpu_set);
> + if (CHECK(err, "set_affinity", "err %d, errno %d\n", err, errno))
> + goto cleanup;
> +
> + pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
> + 0 /* cpu 0 */, -1 /* group id */,
> + 0 /* flags */);
> + if (pmu_fd < 0) {
> + printf("%s:SKIP:cpu doesn't support the event\n", __func__);
> + test__skip();
> + goto cleanup;
> + }
> +
> + skel->links.oncpu = bpf_program__attach_perf_event(skel->progs.oncpu,
> + pmu_fd);
> + if (CHECK(IS_ERR(skel->links.oncpu), "attach_perf_event",
> + "err %ld\n", PTR_ERR(skel->links.oncpu))) {
> + close(pmu_fd);
> + goto cleanup;
> + }
> +
> + /* create kernel and user stack traces for testing */
> + func_6();
> +
> + CHECK(skel->data->stackid_kernel != 2, "get_stackid_kernel", "failed\n");
> + CHECK(skel->data->stackid_user != 2, "get_stackid_user", "failed\n");
> + CHECK(skel->data->stack_kernel != 2, "get_stack_kernel", "failed\n");
> + CHECK(skel->data->stack_user != 2, "get_stack_user", "failed\n");
> + close(pmu_fd);
I think pmu_fd will be closed by perf_event_stackmap__destory (through
closing the link)
> +
> +cleanup:
> + perf_event_stackmap__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/perf_event_stackmap.c b/tools/testing/selftests/bpf/progs/perf_event_stackmap.c
> new file mode 100644
> index 0000000000000..1b0457efeedec
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/perf_event_stackmap.c
> @@ -0,0 +1,64 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2020 Facebook
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +
> +#ifndef PERF_MAX_STACK_DEPTH
> +#define PERF_MAX_STACK_DEPTH 127
> +#endif
> +
> +#ifndef BPF_F_USER_STACK
> +#define BPF_F_USER_STACK (1ULL << 8)
> +#endif
BPF_F_USER_STACK should be in vmlinux.h already, similarly to BPF_F_CURRENT_CPU
> +
> +typedef __u64 stack_trace_t[PERF_MAX_STACK_DEPTH];
> +struct {
> + __uint(type, BPF_MAP_TYPE_STACK_TRACE);
> + __uint(max_entries, 16384);
> + __uint(key_size, sizeof(__u32));
> + __uint(value_size, sizeof(stack_trace_t));
> +} stackmap SEC(".maps");
> +
> +struct {
> + __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
> + __uint(max_entries, 1);
> + __type(key, __u32);
> + __type(value, stack_trace_t);
> +} stackdata_map SEC(".maps");
> +
> +long stackid_kernel = 1;
> +long stackid_user = 1;
> +long stack_kernel = 1;
> +long stack_user = 1;
> +
nit: kind of unusual to go from 1 -> 2, why no zero to one as a flag?
those variables will be available through skel->bss, btw
> +SEC("perf_event")
> +int oncpu(void *ctx)
> +{
> + int max_len = PERF_MAX_STACK_DEPTH * sizeof(__u64);
> + stack_trace_t *trace;
> + __u32 key = 0;
> + long val;
> +
> + val = bpf_get_stackid(ctx, &stackmap, 0);
> + if (val > 0)
> + stackid_kernel = 2;
> + val = bpf_get_stackid(ctx, &stackmap, BPF_F_USER_STACK);
> + if (val > 0)
> + stackid_user = 2;
> +
> + trace = bpf_map_lookup_elem(&stackdata_map, &key);
> + if (!trace)
> + return 0;
> +
> + val = bpf_get_stack(ctx, trace, max_len, 0);
given you don't care about contents of trace, you could have used
`stack_trace_t trace = {}` global variable instead of PERCPU_ARRAY.
> + if (val > 0)
> + stack_kernel = 2;
> +
> + val = bpf_get_stack(ctx, trace, max_len, BPF_F_USER_STACK);
nit: max_len == sizeof(stack_trace_t) ?
> + if (val > 0)
> + stack_user = 2;
> +
> + return 0;
> +}
> +
> +char LICENSE[] SEC("license") = "GPL";
> --
> 2.24.1
>
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