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Date: Tue, 4 Aug 2020 13:08:07 +0300 From: Adrian Hunter <adrian.hunter@...el.com> To: Ian Rogers <irogers@...gle.com>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, Andrii Nakryiko <andriin@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...omium.org>, Andi Kleen <ak@...ux.intel.com>, Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, bpf@...r.kernel.org Cc: Stephane Eranian <eranian@...gle.com> Subject: Re: [PATCH v2 4/5] perf record: Don't clear event's period if set by a term On 28/07/20 11:57 am, Ian Rogers wrote: > 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' Might be worth explaining this use-case some more. Perhaps add it to the leader sampling documentation for perf-list. > would clear the attributes then apply the config terms. In commit > 5f34278867b7 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. > > Fixes: 5f34278867b7 ("perf evlist: Move leader-sampling configuration") > Signed-off-by: Ian Rogers <irogers@...gle.com> > --- > tools/perf/util/record.c | 28 ++++++++++++++++++++-------- > 1 file changed, 20 insertions(+), 8 deletions(-) > > diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c > index a4cc11592f6b..01d1c6c613f7 100644 > --- a/tools/perf/util/record.c > +++ b/tools/perf/util/record.c > @@ -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> > @@ -38,6 +39,9 @@ static void evsel__config_leader_sampling(struct evsel *evsel, struct evlist *ev > struct perf_event_attr *attr = &evsel->core.attr; > struct evsel *leader = evsel->leader; > struct evsel *read_sampler; > + struct evsel_config_term *term; > + struct list_head *config_terms = &evsel->config_terms; > + int term_types, freq_mask; > > if (!leader->sample_read) > return; > @@ -47,16 +51,24 @@ static void evsel__config_leader_sampling(struct evsel *evsel, struct evlist *ev > if (evsel == read_sampler) > return; > > + /* Determine the evsel's config term types. */ > + term_types = 0; > + list_for_each_entry(term, config_terms, list) { > + term_types |= 1 << term->type; > + } > /* > - * 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. > */ > - attr->freq = 0; > - attr->sample_freq = 0; > - attr->sample_period = 0; > - attr->write_backward = 0; > + freq_mask = (1 << EVSEL__CONFIG_TERM_FREQ) | (1 << EVSEL__CONFIG_TERM_PERIOD); > + if ((term_types & freq_mask) == 0) { It would be nicer to have a helper e.g. if (!evsel__have_config_term(evsel, FREQ) && !evsel__have_config_term(evsel, PERIOD)) { > + attr->freq = 0; > + attr->sample_freq = 0; > + attr->sample_period = 0; If we are not sampling, then maybe we should also put here: attr->write_backward = 0; > + } Then, if we are sampling this evsel shouldn't the backward setting match the leader? e.g. if (attr->sample_freq) attr->write_backward = leader->core.attr.write_backward; > + if ((term_types & (1 << EVSEL__CONFIG_TERM_OVERWRITE)) == 0) > + attr->write_backward = 0; > > /* > * We don't get a sample for slave events, we make them when delivering >
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