Commit 685439a7 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
Browse files

perf record: Add cgroup support for off-cpu profiling 



This covers two different use cases.  The first one is cgroup
filtering given by -G/--cgroup option which controls the off-cpu
profiling for tasks in the given cgroups only.

The other use case is cgroup sampling which is enabled by
--all-cgroups option and it adds PERF_SAMPLE_CGROUP to the sample_type
to set the cgroup id of the task in the sample data.

Example output.

  $ sudo perf record -a --off-cpu --all-cgroups sleep 1

  $ sudo perf report --stdio -s comm,cgroup --call-graph=no
  ...
  # Samples: 144  of event 'offcpu-time'
  # Event count (approx.): 48452045427
  #
  # Children      Self  Command          Cgroup
  # ........  ........  ...............  ..........................................
  #
      61.57%     5.60%  Chrome_ChildIOT  /user.slice/user-657345.slice/user@657345.service/app.slice/...
      29.51%     7.38%  Web Content      /user.slice/user-657345.slice/user@657345.service/app.slice/...
      17.48%     1.59%  Chrome_IOThread  /user.slice/user-657345.slice/user@657345.service/app.slice/...
      16.48%     4.12%  pipewire-pulse   /user.slice/user-657345.slice/user@657345.service/session.slice/...
      14.48%     2.07%  perf             /user.slice/user-657345.slice/user@657345.service/app.slice/...
      14.30%     7.15%  CompositorTileW  /user.slice/user-657345.slice/user@657345.service/app.slice/...
      13.33%     6.67%  Timer            /user.slice/user-657345.slice/user@657345.service/app.slice/...
  ...

Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: default avatarIan Rogers <irogers@google.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Blake Jones <blakejones@google.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20220518224725.742882-6-namhyung@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent b36888f7

tools/perf/builtin-record.c

+1 −1
Original line number Diff line number Diff line
@@ -892,7 +892,7 @@ static int record__config_text_poke(struct evlist *evlist) 


static int record__config_off_cpu(struct record *rec)

{

	return off_cpu_prepare(rec->evlist, &rec->opts.target);

	return off_cpu_prepare(rec->evlist, &rec->opts.target, &rec->opts);

}



static bool record__kcore_readable(struct machine *machine)

tools/perf/util/bpf_off_cpu.c

+46 −2
Original line number Diff line number Diff line
@@ -5,10 +5,12 @@ 
#include "util/evlist.h"

#include "util/off_cpu.h"

#include "util/perf-hooks.h"

#include "util/record.h"

#include "util/session.h"

#include "util/target.h"

#include "util/cpumap.h"

#include "util/thread_map.h"

#include "util/cgroup.h"

#include <bpf/bpf.h>



#include "bpf_skel/off_cpu.skel.h"
@@ -24,6 +26,7 @@ struct off_cpu_key { 
	u32 tgid;

	u32 stack_id;

	u32 state;

	u64 cgroup_id;

};



union off_cpu_data {
@@ -116,10 +119,11 @@ static void check_sched_switch_args(void) 
	}

}



int off_cpu_prepare(struct evlist *evlist, struct target *target)

int off_cpu_prepare(struct evlist *evlist, struct target *target,

		    struct record_opts *opts)

{

	int err, fd, i;

	int ncpus = 1, ntasks = 1;

	int ncpus = 1, ntasks = 1, ncgrps = 1;



	if (off_cpu_config(evlist) < 0) {

		pr_err("Failed to config off-cpu BPF event\n");
@@ -143,6 +147,21 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target) 
		bpf_map__set_max_entries(skel->maps.task_filter, ntasks);

	}



	if (evlist__first(evlist)->cgrp) {

		ncgrps = evlist->core.nr_entries - 1; /* excluding a dummy */

		bpf_map__set_max_entries(skel->maps.cgroup_filter, ncgrps);



		if (!cgroup_is_v2("perf_event"))

			skel->rodata->uses_cgroup_v1 = true;

	}



	if (opts->record_cgroup) {

		skel->rodata->needs_cgroup = true;



		if (!cgroup_is_v2("perf_event"))

			skel->rodata->uses_cgroup_v1 = true;

	}



	set_max_rlimit();

	check_sched_switch_args();
@@ -178,6 +197,29 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target) 
		}

	}



	if (evlist__first(evlist)->cgrp) {

		struct evsel *evsel;

		u8 val = 1;



		skel->bss->has_cgroup = 1;

		fd = bpf_map__fd(skel->maps.cgroup_filter);



		evlist__for_each_entry(evlist, evsel) {

			struct cgroup *cgrp = evsel->cgrp;



			if (cgrp == NULL)

				continue;



			if (!cgrp->id && read_cgroup_id(cgrp) < 0) {

				pr_err("Failed to read cgroup id of %s\n",

				       cgrp->name);

				goto out;

			}



			bpf_map_update_elem(fd, &cgrp->id, &val, BPF_ANY);

		}

	}



	err = off_cpu_bpf__attach(skel);

	if (err) {

		pr_err("Failed to attach off-cpu BPF skeleton\n");
@@ -275,6 +317,8 @@ int off_cpu_write(struct perf_session *session) 
			/* calculate sample callchain data array length */

			n += len + 2;

		}

		if (sample_type & PERF_SAMPLE_CGROUP)

			data.array[n++] = key.cgroup_id;

		/* TODO: handle more sample types */



		size = n * sizeof(u64);

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

+33 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ struct offcpu_key { 
	__u32 tgid;

	__u32 stack_id;

	__u32 state;

	__u64 cgroup_id;

};



struct {
@@ -63,6 +64,13 @@ struct { 
	__uint(max_entries, 1);

} task_filter SEC(".maps");



struct {

	__uint(type, BPF_MAP_TYPE_HASH);

	__uint(key_size, sizeof(__u64));

	__uint(value_size, sizeof(__u8));

	__uint(max_entries, 1);

} cgroup_filter SEC(".maps");



/* old kernel task_struct definition */

struct task_struct___old {

	long state;
@@ -71,8 +79,11 @@ struct task_struct___old { 
int enabled = 0;

int has_cpu = 0;

int has_task = 0;

int has_cgroup = 0;



const volatile bool has_prev_state = false;

const volatile bool needs_cgroup = false;

const volatile bool uses_cgroup_v1 = false;



/*

 * Old kernel used to call it task_struct->state and now it's '__state'.
@@ -92,6 +103,18 @@ static inline int get_task_state(struct task_struct *t) 
	return BPF_CORE_READ(t_old, state);

}



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);



	return BPF_CORE_READ(cgrp, kn, id);

}



static inline int can_record(struct task_struct *t, int state)

{

	/* kernel threads don't have user stack */
@@ -120,6 +143,15 @@ static inline int can_record(struct task_struct *t, int state) 
			return 0;

	}



	if (has_cgroup) {

		__u8 *ok;

		__u64 cgrp_id = get_cgroup_id(t);



		ok = bpf_map_lookup_elem(&cgroup_filter, &cgrp_id);

		if (!ok)

			return 0;

	}



	return 1;

}
@@ -156,6 +188,7 @@ static int off_cpu_stat(u64 *ctx, struct task_struct *prev, 
			.tgid = next->tgid,

			.stack_id = pelem->stack_id,

			.state = pelem->state,

			.cgroup_id = needs_cgroup ? get_cgroup_id(next) : 0,

		};

		__u64 delta = ts - pelem->timestamp;

		__u64 *total;

tools/perf/util/off_cpu.h

+5 −2
Original line number Diff line number Diff line
@@ -4,15 +4,18 @@ 
struct evlist;

struct target;

struct perf_session;

struct record_opts;



#define OFFCPU_EVENT  "offcpu-time"



#ifdef HAVE_BPF_SKEL

int off_cpu_prepare(struct evlist *evlist, struct target *target);

int off_cpu_prepare(struct evlist *evlist, struct target *target,

		    struct record_opts *opts);

int off_cpu_write(struct perf_session *session);

#else

static inline int off_cpu_prepare(struct evlist *evlist __maybe_unused,

				  struct target *target __maybe_unused)

				  struct target *target __maybe_unused,

				  struct record_opts *opts __maybe_unused)

{

	return -1;

}