From: Ian Rogers <irogers@google.com>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Jiri Olsa <jolsa@kernel.org>, Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
linux-perf-users@vger.kernel.org,
Song Liu <songliubraving@fb.com>, Hao Luo <haoluo@google.com>,
bpf@vger.kernel.org
Subject: Re: [PATCH v4] perf tools: Get a perf cgroup more portably in BPF
Date: Fri, 23 Sep 2022 09:45:19 -0700 [thread overview]
Message-ID: <CAP-5=fWwNwtocMR3s1Su2k2vZAwL4yhX19UGZ4i0dMXFDFFBJA@mail.gmail.com> (raw)
In-Reply-To: <20220923063205.772936-1-namhyung@kernel.org>
On Thu, Sep 22, 2022 at 11:32 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> The perf_event_cgrp_id can be different on other configurations.
> To be more portable as CO-RE, it needs to get the cgroup subsys id
> using the bpf_core_enum_value() helper.
>
> Suggested-by: Ian Rogers <irogers@google.com>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Ian Rogers <irogers@google.com>
Would be good to get this into perf/urgent, does it need Fixes tags for that?
Thanks,
Ian
> ---
> v4 changes)
> * add a missing check in the off_cpu
>
> v3 changes)
> * check compiler features for enum value
>
> v2 changes)
> * fix off_cpu.bpf.c too
> * get perf_subsys_id only once
>
> tools/perf/util/bpf_skel/bperf_cgroup.bpf.c | 11 ++++++++++-
> tools/perf/util/bpf_skel/off_cpu.bpf.c | 18 ++++++++++++++----
> 2 files changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
> index 292c430768b5..8e7520e273db 100644
> --- a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
> +++ b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
> @@ -48,6 +48,7 @@ const volatile __u32 num_cpus = 1;
>
> int enabled = 0;
> int use_cgroup_v2 = 0;
> +int perf_subsys_id = -1;
>
> static inline int get_cgroup_v1_idx(__u32 *cgrps, int size)
> {
> @@ -58,7 +59,15 @@ static inline int get_cgroup_v1_idx(__u32 *cgrps, int size)
> int level;
> int cnt;
>
> - cgrp = BPF_CORE_READ(p, cgroups, subsys[perf_event_cgrp_id], cgroup);
> + if (perf_subsys_id == -1) {
> +#if __has_builtin(__builtin_preserve_enum_value)
> + perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id,
> + perf_event_cgrp_id);
> +#else
> + perf_subsys_id = perf_event_cgrp_id;
> +#endif
> + }
> + cgrp = BPF_CORE_READ(p, cgroups, subsys[perf_subsys_id], cgroup);
> level = BPF_CORE_READ(cgrp, level);
>
> for (cnt = 0; i < MAX_LEVELS; i++) {
> diff --git a/tools/perf/util/bpf_skel/off_cpu.bpf.c b/tools/perf/util/bpf_skel/off_cpu.bpf.c
> index c4ba2bcf179f..38e3b287dbb2 100644
> --- a/tools/perf/util/bpf_skel/off_cpu.bpf.c
> +++ b/tools/perf/util/bpf_skel/off_cpu.bpf.c
> @@ -94,6 +94,8 @@ const volatile bool has_prev_state = false;
> const volatile bool needs_cgroup = false;
> const volatile bool uses_cgroup_v1 = false;
>
> +int perf_subsys_id = -1;
> +
> /*
> * Old kernel used to call it task_struct->state and now it's '__state'.
> * Use BPF CO-RE "ignored suffix rule" to deal with it like below:
> @@ -119,11 +121,19 @@ static inline __u64 get_cgroup_id(struct task_struct *t)
> {
> struct cgroup *cgrp;
>
> - if (uses_cgroup_v1)
> - cgrp = BPF_CORE_READ(t, cgroups, subsys[perf_event_cgrp_id], cgroup);
> - else
> - cgrp = BPF_CORE_READ(t, cgroups, dfl_cgrp);
> + if (!uses_cgroup_v1)
> + return BPF_CORE_READ(t, cgroups, dfl_cgrp, kn, id);
> +
> + if (perf_subsys_id == -1) {
> +#if __has_builtin(__builtin_preserve_enum_value)
> + perf_subsys_id = bpf_core_enum_value(enum cgroup_subsys_id,
> + perf_event_cgrp_id);
> +#else
> + perf_subsys_id = perf_event_cgrp_id;
> +#endif
> + }
>
> + cgrp = BPF_CORE_READ(t, cgroups, subsys[perf_subsys_id], cgroup);
> return BPF_CORE_READ(cgrp, kn, id);
> }
>
> --
> 2.37.3.998.g577e59143f-goog
>
next prev parent reply other threads:[~2022-09-23 16:45 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-23 6:32 [PATCH v4] perf tools: Get a perf cgroup more portably in BPF Namhyung Kim
2022-09-23 16:45 ` Ian Rogers [this message]
2022-09-26 13:11 ` Arnaldo Carvalho de Melo
2022-09-26 13:06 ` Arnaldo Carvalho de Melo
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