From: Ian Rogers <irogers@google.com>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>, Andi Kleen <ak@linux.intel.com>,
Athira Rajeev <atrajeev@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH v2 4/5] perf record: Don't clear event's period if set by a term
Date: Tue, 4 Aug 2020 06:33:47 -0700 [thread overview]
Message-ID: <CAP-5=fUCnBGX0L0Tt3_gmVnt+hvaouJMx6XFErFKk72+xuw9fw@mail.gmail.com> (raw)
In-Reply-To: <969ef797-59ea-69d0-24b9-33bcdff106a1@intel.com>
On Tue, Aug 4, 2020 at 3:08 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>
> 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@google.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)) {
Sure. The point of doing it this way was to avoid repeatedly iterating
over the config term list.
> > + 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;
Perhaps that should be a follow up change? This change is trying to
make the behavior match the previous behavior.
Thanks,
Ian
> > + 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
> >
>
next prev parent reply other threads:[~2020-08-04 13:34 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-28 8:57 [PATCH v2 0/5] Fixes for setting event freq/periods Ian Rogers
2020-07-28 8:57 ` [PATCH v2 1/5] perf record: Set PERF_RECORD_PERIOD if attr->freq is set Ian Rogers
2020-07-28 15:43 ` Jiri Olsa
2020-07-28 16:03 ` Arnaldo Carvalho de Melo
2020-07-29 15:11 ` Athira Rajeev
2020-07-29 18:52 ` Arnaldo Carvalho de Melo
2020-07-29 21:43 ` Ian Rogers
2020-09-04 5:39 ` Ian Rogers
2020-07-28 8:57 ` [PATCH v2 2/5] perf record: Prevent override of attr->sample_period for libpfm4 events Ian Rogers
2020-07-28 15:59 ` Jiri Olsa
2020-07-28 16:09 ` Jiri Olsa
2020-07-29 23:24 ` Ian Rogers
2020-09-04 5:41 ` Ian Rogers
2020-09-04 16:03 ` Jiri Olsa
2020-09-04 16:22 ` Ian Rogers
2020-09-04 18:48 ` Arnaldo Carvalho de Melo
2020-09-04 18:50 ` Arnaldo Carvalho de Melo
2020-09-04 18:51 ` Arnaldo Carvalho de Melo
2020-09-11 22:34 ` Ian Rogers
2020-09-12 3:02 ` Ian Rogers
2020-07-29 18:54 ` Arnaldo Carvalho de Melo
2020-07-28 8:57 ` [PATCH v2 3/5] perf test: Ensure sample_period is set " Ian Rogers
2020-07-28 12:45 ` Arnaldo Carvalho de Melo
2020-07-28 8:57 ` [PATCH v2 4/5] perf record: Don't clear event's period if set by a term Ian Rogers
2020-07-29 18:58 ` Arnaldo Carvalho de Melo
2020-08-04 10:08 ` Adrian Hunter
2020-08-04 13:33 ` Ian Rogers [this message]
2020-08-04 14:48 ` Adrian Hunter
2020-08-04 15:50 ` Ian Rogers
2020-09-04 5:43 ` Ian Rogers
2020-09-07 6:36 ` Adrian Hunter
2020-07-28 8:57 ` [PATCH v2 5/5] perf test: Leader sampling shouldn't clear sample period Ian Rogers
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