Commit 3b0a18c1 authored Sep 11, 2020 by Ian Rogers Committed by Arnaldo Carvalho de Melo Sep 14, 2020

perf record: Don't clear event's period if set by a term



If events in a group explicitly set a frequency or period with leader
sampling, don't disable the samples on those events.

Prior to 5.8:

  perf record -e '{cycles/period=12345000/,instructions/period=6789000/}:S'

would clear the attributes then apply the config terms. In commit
5f342788 leader sampling configuration was moved to after applying the
config terms, in the example, making the instructions' event have its period
cleared.

This change makes it so that sampling is only disabled if configuration
terms aren't present.

Committer testing:

Before:

  # perf record -e '{cycles/period=1/,instructions/period=2/}:S' sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.051 MB perf.data (6 samples) ]
  #
  # perf evlist -v
  cycles/period=1/: size: 120, { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|READ|ID, read_format: ID|GROUP, disabled: 1, mmap: 1, comm: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1
  instructions/period=2/: size: 120, config: 0x1, sample_type: IP|TID|TIME|READ|ID, read_format: ID|GROUP, sample_id_all: 1, exclude_guest: 1
  #

After:

  # perf record -e '{cycles/period=1/,instructions/period=2/}:S' sleep 0.0001
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.052 MB perf.data (4 samples) ]
  # perf evlist -v
  cycles/period=1/: size: 120, { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|READ|ID, read_format: ID|GROUP, disabled: 1, mmap: 1, comm: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1
  instructions/period=2/: size: 120, config: 0x1, { sample_period, sample_freq }: 2, sample_type: IP|TID|TIME|READ|ID, read_format: ID|GROUP, sample_id_all: 1, exclude_guest: 1
  #

Fixes: 5f342788 ("perf evlist: Move leader-sampling configuration")
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Yonghong Song <yhs@fb.com>
Link: http://lore.kernel.org/lkml/20200912025655.1337192-4-irogers@google.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent 2fa3fc95

tools/perf/util/record.c

+26 −8

Original line number	Diff line number	Diff line
		@@ -2,6 +2,7 @@
		#include "debug.h"
		#include "evlist.h"
		#include "evsel.h"
		#include "evsel_config.h"
		#include "parse-events.h"
		#include <errno.h>
		#include <limits.h>
		@@ -33,11 +34,24 @@ static struct evsel evsel__read_sampler(struct evsel evsel, struct evlist *evl
		return leader;
		}

		static u64 evsel__config_term_mask(struct evsel *evsel)
		{
		struct evsel_config_term *term;
		struct list_head *config_terms = &evsel->config_terms;
		u64 term_types = 0;

		list_for_each_entry(term, config_terms, list) {
		term_types \|= 1 << term->type;
		}
		return term_types;
		}

		static void evsel__config_leader_sampling(struct evsel evsel, struct evlist evlist)
		{
		struct perf_event_attr *attr = &evsel->core.attr;
		struct evsel *leader = evsel->leader;
		struct evsel *read_sampler;
		u64 term_types, freq_mask;

		if (!leader->sample_read)
		return;
		@@ -47,15 +61,19 @@ static void evsel__config_leader_sampling(struct evsel evsel, struct evlist ev
		if (evsel == read_sampler)
		return;

		term_types = evsel__config_term_mask(evsel);
		/*
		* Disable sampling for all group members other than the leader in
		* case the leader 'leads' the sampling, except when the leader is an
		* AUX area event, in which case the 2nd event in the group is the one
		* that 'leads' the sampling.
		* Disable sampling for all group members except those with explicit
		* config terms or the leader. In the case of an AUX area event, the 2nd
		* event in the group is the one that 'leads' the sampling.
		*/
		freq_mask = (1 << EVSEL__CONFIG_TERM_FREQ) \| (1 << EVSEL__CONFIG_TERM_PERIOD);
		if ((term_types & freq_mask) == 0) {
		attr->freq = 0;
		attr->sample_freq = 0;
		attr->sample_period = 0;
		}
		if ((term_types & (1 << EVSEL__CONFIG_TERM_OVERWRITE)) == 0)
		attr->write_backward = 0;

		/*

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