Commit e42c9c54 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
Browse files

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: default avatarIan Rogers <irogers@google.com>
Reviewed-by: default avatarIan Rogers <irogers@google.com>
Signed-off-by: default avatarNamhyung 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent f76349cf

tools/perf/util/bpf_skel/bperf_cgroup.bpf.c

+10 −1
Original line number Diff line number Diff line
@@ -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++) {

tools/perf/util/bpf_skel/off_cpu.bpf.c

+14 −4
Original line number Diff line number Diff line
@@ -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);

}