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Message-ID: <CAP-5=fUL=KVpsd7rPOsWuML2iJGjciUe15Svdux67OsAngST1A@mail.gmail.com>
Date: Wed, 18 May 2022 21:07:00 -0700
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
Jiri Olsa <jolsa@...nel.org>, Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
LKML <linux-kernel@...r.kernel.org>,
Andi Kleen <ak@...ux.intel.com>,
Song Liu <songliubraving@...com>, Hao Luo <haoluo@...gle.com>,
Milian Wolff <milian.wolff@...b.com>, bpf@...r.kernel.org,
linux-perf-users@...r.kernel.org,
Blake Jones <blakejones@...gle.com>
Subject: Re: [PATCH 5/6] perf record: Add cgroup support for off-cpu profiling
On Wed, May 18, 2022 at 3:47 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> 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@...345.service/app.slice/...
> 29.51% 7.38% Web Content /user.slice/user-657345.slice/user@...345.service/app.slice/...
> 17.48% 1.59% Chrome_IOThread /user.slice/user-657345.slice/user@...345.service/app.slice/...
> 16.48% 4.12% pipewire-pulse /user.slice/user-657345.slice/user@...345.service/session.slice/...
> 14.48% 2.07% perf /user.slice/user-657345.slice/user@...345.service/app.slice/...
> 14.30% 7.15% CompositorTileW /user.slice/user-657345.slice/user@...345.service/app.slice/...
> 13.33% 6.67% Timer /user.slice/user-657345.slice/user@...345.service/app.slice/...
> ...
>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
Acked-by: Ian Rogers <irogers@...gle.com>
Thanks,
Ian
> ---
> tools/perf/builtin-record.c | 2 +-
> tools/perf/util/bpf_off_cpu.c | 48 ++++++++++++++++++++++++--
> tools/perf/util/bpf_skel/off_cpu.bpf.c | 33 ++++++++++++++++++
> tools/perf/util/off_cpu.h | 7 ++--
> 4 files changed, 85 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 7f60d2eac0b4..77fa21c2c69f 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -907,7 +907,7 @@ 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)
> diff --git a/tools/perf/util/bpf_off_cpu.c b/tools/perf/util/bpf_off_cpu.c
> index 874856c55101..b73e84a02264 100644
> --- a/tools/perf/util/bpf_off_cpu.c
> +++ b/tools/perf/util/bpf_off_cpu.c
> @@ -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);
> diff --git a/tools/perf/util/bpf_skel/off_cpu.bpf.c b/tools/perf/util/bpf_skel/off_cpu.bpf.c
> index 986d7db6e75d..792ae2847080 100644
> --- a/tools/perf/util/bpf_skel/off_cpu.bpf.c
> +++ b/tools/perf/util/bpf_skel/off_cpu.bpf.c
> @@ -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;
> diff --git a/tools/perf/util/off_cpu.h b/tools/perf/util/off_cpu.h
> index f47af0232e55..548008f74d42 100644
> --- a/tools/perf/util/off_cpu.h
> +++ b/tools/perf/util/off_cpu.h
> @@ -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;
> }
> --
> 2.36.1.124.g0e6072fb45-goog
>
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