perf stat: Support old kernels for bperf cgroup counting

The recent change in the cgroup will break the backward compatiblity in
the BPF program. It should support both old and new kernels using BPF
CO-RE technique.

Like the task_struct->__state handling in the offcpu analysis, we can
check the field name in the cgroup struct.

Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

perf stat: Support old kernels for bperf cgroup counting

The recent change in the cgroup will break the backward compatiblity in
the BPF program. It should support both old and new kernels using BPF
CO-RE technique.

Like the task_struct->__state handling in the offcpu analysis, we can
check the field name in the cgroup struct.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: bpf@vger.kernel.org
Cc: cgroups@vger.kernel.org
Cc: zefan li <lizefan.x@bytedance.com>
Link: http://lore.kernel.org/lkml/20221011052808.282394-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

cgroup: Replace cgroup->ancestor_ids[] with ->ancestors[]

Every cgroup knows all its ancestors through its ->ancestor_ids[]. There's
no advantage to remembering the IDs instead of the pointers directly and
this makes the array useless for finding an actual ancestor cgroup forcing
cgroup_ancestor() to iteratively walk up the hierarchy instead. Let's
replace cgroup->ancestor_ids[] with ->ancestors[] and remove the walking-up
from cgroup_ancestor().

While at it, improve comments around cgroup_root->cgrp_ancestor_storage.

This patch shouldn't cause user-visible behavior differences.

v2: Update cgroup_ancestor() to use ->ancestors[].

v3: cgroup_root->cgrp_ancestor_storage's type is updated to match
cgroup->ancestors[]. Better comments.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>

perf tools: Get a perf cgroup more portably in BPF

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>
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20220923063205.772936-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

perf stat: Fix BPF program section name

It seems the recent libbpf got more strict about the section name.
I'm seeing a failure like this:

$ sudo ./perf stat -a --bpf-counters --for-each-cgroup ^. sleep 1
libbpf: prog 'on_cgrp_switch': missing BPF prog type, check ELF section name 'perf_events'
libbpf: prog 'on_cgrp_switch': failed to load: -22
libbpf: failed to load object 'bperf_cgroup_bpf'
libbpf: failed to load BPF skeleton 'bperf_cgroup_bpf': -22
Failed to load cgroup skeleton

The section name should be 'perf_event' (without the trailing 's').
Although it's related to the libbpf change, it'd be better fix the
section name in the first place.

Fixes: 944138f048f7d759 ("perf stat: Enable BPF counter with --for-each-cgroup")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: bpf@vger.kernel.org
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/r/20220916184132.1161506-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

perf stat: Enable BPF counter with --for-each-cgroup

Recently bperf was added to use BPF to count perf events for various
purposes. This is an extension for the approach and targetting to
cgroup usages.

Unlike the other bperf, it doesn't share the events with other
processes but it'd reduce unnecessary events (and the overhead of
multiplexing) for each monitored cgroup within the perf session.

When --for-each-cgroup is used with --bpf-counters, it will open
cgroup-switches event per cpu internally and attach the new BPF
program to read given perf_events and to aggregate the results for
cgroups. It's only called when task is switched to a task in a
different cgroup.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20210701211227.1403788-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>