Messages in this thread | | | From | Namhyung Kim <> | Date | Wed, 30 Jun 2021 13:09:52 -0700 | Subject | Re: [PATCH 4/4] perf stat: Enable BPF counter with --for-each-cgroup |
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Hi Song,
On Wed, Jun 30, 2021 at 11:47 AM Song Liu <songliubraving@fb.com> wrote: > > > > > On Jun 25, 2021, at 12:18 AM, Namhyung Kim <namhyung@kernel.org> wrote: > > > > 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. > > > > Cc: Song Liu <songliubraving@fb.com> > > Signed-off-by: Namhyung Kim <namhyung@kernel.org> > > --- > > tools/perf/Makefile.perf | 17 +- > > tools/perf/util/Build | 1 + > > tools/perf/util/bpf_counter.c | 5 + > > tools/perf/util/bpf_counter_cgroup.c | 299 ++++++++++++++++++++ > > tools/perf/util/bpf_skel/bperf_cgroup.bpf.c | 191 +++++++++++++ > > tools/perf/util/cgroup.c | 2 + > > tools/perf/util/cgroup.h | 1 + > > 7 files changed, 515 insertions(+), 1 deletion(-) > > create mode 100644 tools/perf/util/bpf_counter_cgroup.c > > create mode 100644 tools/perf/util/bpf_skel/bperf_cgroup.bpf.c > > [...] > > > diff --git a/tools/perf/util/bpf_counter_cgroup.c b/tools/perf/util/bpf_counter_cgroup.c > > new file mode 100644 > > index 000000000000..327f97a23a84 > > --- /dev/null > > +++ b/tools/perf/util/bpf_counter_cgroup.c > > @@ -0,0 +1,299 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > + > > +/* Copyright (c) 2019 Facebook */ > > I am not sure whether this ^^^ is accurate.
Well, I just copied it from the bpf_counter.c file which was the base of this patch. Now I don't think I have many lines of code directly came from the origin.
So I'm not sure what I can do. Do you want to update the copyright year to 2021? Or are you ok with removing the line at all?
> > > +/* Copyright (c) 2021 Google */ > > + > > +#include <assert.h> > > +#include <limits.h> > > +#include <unistd.h> > > +#include <sys/file.h> > > +#include <sys/time.h> > > +#include <sys/resource.h> > > +#include <linux/err.h> > > +#include <linux/zalloc.h> > > +#include <linux/perf_event.h> > > +#include <api/fs/fs.h> > > +#include <perf/bpf_perf.h> > > + > > +#include "affinity.h" > > +#include "bpf_counter.h" > > +#include "cgroup.h" > > +#include "counts.h" > > +#include "debug.h" > > +#include "evsel.h" > > +#include "evlist.h" > > +#include "target.h" > > +#include "cpumap.h" > > +#include "thread_map.h" > > + > > +#include "bpf_skel/bperf_cgroup.skel.h" > > + > > +static struct perf_event_attr cgrp_switch_attr = { > > + .type = PERF_TYPE_SOFTWARE, > > + .config = PERF_COUNT_SW_CGROUP_SWITCHES, > > + .size = sizeof(cgrp_switch_attr), > > + .sample_period = 1, > > + .disabled = 1, > > +}; > > + > > +static struct evsel *cgrp_switch; > > +static struct bperf_cgroup_bpf *skel; > > + > > +#define FD(evt, cpu) (*(int *)xyarray__entry(evt->core.fd, cpu, 0)) > > + > > +static int bperf_load_program(struct evlist *evlist) > > +{ > > + struct bpf_link *link; > > + struct evsel *evsel; > > + struct cgroup *cgrp, *leader_cgrp; > > + __u32 i, cpu; > > + int nr_cpus = evlist->core.all_cpus->nr; > > + int total_cpus = cpu__max_cpu(); > > + int map_size, map_fd; > > + int prog_fd, err; > > + > > + skel = bperf_cgroup_bpf__open(); > > + if (!skel) { > > + pr_err("Failed to open cgroup skeleton\n"); > > + return -1; > > + } > > + > > + skel->rodata->num_cpus = total_cpus; > > + skel->rodata->num_events = evlist->core.nr_entries / nr_cgroups; > > + > > + BUG_ON(evlist->core.nr_entries % nr_cgroups != 0); > > + > > + /* we need one copy of events per cpu for reading */ > > + map_size = total_cpus * evlist->core.nr_entries / nr_cgroups; > > + bpf_map__resize(skel->maps.events, map_size); > > + bpf_map__resize(skel->maps.cgrp_idx, nr_cgroups); > > + /* previous result is saved in a per-cpu array */ > > + map_size = evlist->core.nr_entries / nr_cgroups; > > + bpf_map__resize(skel->maps.prev_readings, map_size); > > + /* cgroup result needs all events (per-cpu) */ > > + map_size = evlist->core.nr_entries; > > + bpf_map__resize(skel->maps.cgrp_readings, map_size); > > + > > + set_max_rlimit(); > > + > > + err = bperf_cgroup_bpf__load(skel); > > + if (err) { > > + pr_err("Failed to load cgroup skeleton\n"); > > + goto out; > > + } > > + > > + if (cgroup_is_v2("perf_event") > 0) > > + skel->bss->use_cgroup_v2 = 1; > > + > > + err = -1; > > + > > + cgrp_switch = evsel__new(&cgrp_switch_attr); > > + if (evsel__open_per_cpu(cgrp_switch, evlist->core.all_cpus, -1) < 0) { > > + pr_err("Failed to open cgroup switches event\n"); > > + goto out; > > + } > > + > > + for (i = 0; i < nr_cpus; i++) { > > + link = bpf_program__attach_perf_event(skel->progs.on_cgrp_switch, > > + FD(cgrp_switch, i)); > > + if (IS_ERR(link)) { > > + pr_err("Failed to attach cgroup program\n"); > > + err = PTR_ERR(link); > > + goto out; > > + } > > + } > > + > > + /* > > + * Update cgrp_idx map from cgroup-id to event index. > > + */ > > + cgrp = NULL; > > + i = 0; > > + > > + evlist__for_each_entry(evlist, evsel) { > > + if (cgrp == NULL || evsel->cgrp == leader_cgrp) { > > + leader_cgrp = evsel->cgrp; > > + evsel->cgrp = NULL; > > + > > + /* open single copy of the events w/o cgroup */ > > + err = evsel__open_per_cpu(evsel, evlist->core.all_cpus, -1); > > + if (err) { > > + pr_err("Failed to open first cgroup events\n"); > > + goto out; > > + } > > + > > + map_fd = bpf_map__fd(skel->maps.events); > > + for (cpu = 0; cpu < nr_cpus; cpu++) { > > + int fd = FD(evsel, cpu); > > + __u32 idx = evsel->idx * total_cpus + > > + evlist->core.all_cpus->map[cpu]; > > + > > + err = bpf_map_update_elem(map_fd, &idx, &fd, > > + BPF_ANY); > > + if (err < 0) { > > + pr_err("Failed to update perf_event fd\n"); > > + goto out; > > + } > > + } > > + > > + evsel->cgrp = leader_cgrp; > > + } > > + evsel->supported = true; > > + > > + if (evsel->cgrp == cgrp) > > + continue; > > + > > + cgrp = evsel->cgrp; > > + > > + if (read_cgroup_id(cgrp) < 0) { > > + pr_err("Failed to get cgroup id\n"); > > + err = -1; > > + goto out; > > + } > > + > > + map_fd = bpf_map__fd(skel->maps.cgrp_idx); > > + err = bpf_map_update_elem(map_fd, &cgrp->id, &i, BPF_ANY); > > + if (err < 0) { > > + pr_err("Failed to update cgroup index map\n"); > > + goto out; > > + } > > + > > + i++; > > + } > > + > > + /* > > + * bperf uses BPF_PROG_TEST_RUN to get accurate reading. Check > > + * whether the kernel support it > > + */ > > + prog_fd = bpf_program__fd(skel->progs.trigger_read); > > + err = bperf_trigger_reading(prog_fd, 0); > > + if (err) { > > + pr_debug("The kernel does not support test_run for raw_tp BPF programs.\n" > > + "Therefore, --for-each-cgroup might show inaccurate readings\n"); > > I think this should be a warning, and we should set err = 0 to continue?
Sounds good, will change.
> > > + } > > + > > +out: > > + return err; > > +} > > + > > [...] > > > + > > +/* > > + * trigger the leader prog on each cpu, so the cgrp_reading map could get > > + * the latest results. > > + */ > > +static int bperf_cgrp__sync_counters(struct evlist *evlist) > > +{ > > + int i, cpu; > > + int nr_cpus = evlist->core.all_cpus->nr; > > + int prog_fd = bpf_program__fd(skel->progs.trigger_read); > > + > > + for (i = 0; i < nr_cpus; i++) { > > + cpu = evlist->core.all_cpus->map[i]; > > + bperf_trigger_reading(prog_fd, cpu); > > + } > > + > > + return 0; > > +} > > + > > +static int bperf_cgrp__enable(struct evsel *evsel) > > +{ > > Do we need to call bperf_cgrp__sync_counters() before setting enabled to 1? > If we don't, we may count some numbers before setting enabled to 1, no?
Actually it'll update the prev_readings even if enabled = 0. So I think it should get the correct counts after setting it to 1 without the bperf_cgrp__sync_counters().
Thanks, Namhyung
> > > + skel->bss->enabled = 1; > > + return 0; > > +} > > [...] >
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