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Date: Mon, 14 Nov 2022 06:09:17 -0800
From: Ian Rogers <irogers@...gle.com>
To: "Liang, Kan" <kan.liang@...ux.intel.com>
Cc: Weilin Wang <weilin.wang@...el.com>,
Perry Taylor <perry.taylor@...el.com>,
Caleb Biggers <caleb.biggers@...el.com>,
Leo Yan <leo.yan@...aro.org>,
Adrian Hunter <adrian.hunter@...el.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@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Sandipan Das <sandipan.das@....com>,
Kajol Jain <kjain@...ux.ibm.com>,
Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
Ravi Bangoria <ravi.bangoria@....com>,
Xin Gao <gaoxin@...rlc.com>, Rob Herring <robh@...nel.org>,
linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v1 1/9] perf pmu: Add documentation
On Mon, Nov 14, 2022 at 5:40 AM Liang, Kan <kan.liang@...ux.intel.com> wrote:
>
>
>
> On 2022-11-14 2:51 a.m., Ian Rogers wrote:
> > Add documentation to struct perf_pmu and the associated structs of
> > perf_pmu_alias and perf_pmu_format.
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> > tools/perf/util/pmu.c | 14 ++++++
> > tools/perf/util/pmu.h | 105 +++++++++++++++++++++++++++++++++++++++---
> > 2 files changed, 113 insertions(+), 6 deletions(-)
> >
> > diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> > index 6a86e6af0903..a8f9f47c6ed9 100644
> > --- a/tools/perf/util/pmu.c
> > +++ b/tools/perf/util/pmu.c
> > @@ -31,10 +31,24 @@
> >
> > struct perf_pmu perf_pmu__fake;
> >
> > +/**
> > + * Values from a format file read from <sysfs>/devices/cpu/format/ held in
> > + * struct perf_pmu. For example, the contents of
> > + * <sysfs>/devices/cpu/format/event may be "config:0-7" and will be represented
> > + * here as name="event", value=PERF_PMU_FORMAT_VALUE_CONFIG and bits 0 to 7 will
> > + * be set.
> > + */
> > struct perf_pmu_format {
> > + /** The modifier/file name. */
> > char *name;
> > + /**
> > + * Which config value the format relates to. Supported values are from
> > + * PERF_PMU_FORMAT_VALUE_CONFIG to PERF_PMU_FORMAT_VALUE_CONFIG_END.
> > + */
> > int value;
> > + /** Which config bits are set by this format value. */
> > DECLARE_BITMAP(bits, PERF_PMU_FORMAT_BITS);
> > + /** Element on list within struct perf_pmu. */
> > struct list_head list;
> > };
> >
> > diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
> > index 68e15c38ae71..29571c0f9d15 100644
> > --- a/tools/perf/util/pmu.h
> > +++ b/tools/perf/util/pmu.h
> > @@ -34,30 +34,91 @@ struct perf_pmu_caps {
> > };
> >
> > struct perf_pmu {
> > + /** The name of the PMU such as "cpu". */
> > char *name;
> > + /**
> > + * Optional alternate name for the PMU determined in architecture
> > + * specific code.
> > + */
> > char *alias_name;
> > + /**
> > + * Optional PMU identifier read from
> > + * <sysfs>/bus/event_source/devices/<name>/identifier.
> > + */
> > char *id;
> > + /**
> > + * Perf event attributed type value, read from
> > + * <sysfs>/bus/event_source/devices/<name>/type.
> > + */
> > __u32 type;
> > + /**
> > + * Can the PMU name be selected as if it were an event?
> > + */
> > bool selectable;
> > + /**
> > + * Is the PMU not within the CPU core? Determined by the presence of
> > + * <sysfs>/bus/event_source/devices/<name>/cpumask.
> > + */
> > bool is_uncore;
> > + /** Is the PMU name either cpu_core or cpu_atom. */
>
> I don't think we want to limit the hybrid names only to cpu_core or
> cpu_atom. Maybe something as below?
> /* Is a hybrid CPU PMU, e.g., cpu_core, cpu_atom. */
Currently the hybrid code only works for cpu_core or cpu_atom, a
limitation of its implementation. As pointed out in a later patch,
this bool isn't being used when it could be and I think we can work to
remove it. It would be possible to remove all uses of this with
perf_pmu__is_hybrid. As such I think it may be useful to mark the
hybrid variables in struct perf_pmu as deprecated while we work to
replace their use with more generic just any PMU code.
Thanks,
Ian
> Thanks,
> Kan
>
> > bool is_hybrid;
> > + /**
> > + * Are events auxiliary events? Determined in architecture specific
> > + * code.
> > + */
> > bool auxtrace;
> > + /**
> > + * Number of levels of :ppp precision supported by the PMU, read from
> > + * <sysfs>/bus/event_source/devices/<name>/caps/max_precise.
> > + */
> > int max_precise;
> > + /**
> > + * Optional default perf_event_attr determined in architecture specific
> > + * code.
> > + */
> > struct perf_event_attr *default_config;
> > + /**
> > + * Empty or the contents of either of:
> > + * <sysfs>/bus/event_source/devices/<name>/cpumask.
> > + * <sysfs>/bus/event_source/devices/<cpu>/cpus.
> > + */
> > struct perf_cpu_map *cpus;
> > - struct list_head format; /* HEAD struct perf_pmu_format -> list */
> > - struct list_head aliases; /* HEAD struct perf_pmu_alias -> list */
> > + /**
> > + * Holds the contents of files read from
> > + * <sysfs>/bus/event_source/devices/<name>/format/. The contents specify
> > + * which event parameter changes what config, config1 or config2 bits.
> > + */
> > + struct list_head format;
> > + /**
> > + * List of struct perf_pmu_alias. Each alias corresponds to an event
> > + * read from <sysfs>/bus/event_source/devices/<name>/events/ or from
> > + * json events in pmu-events.c.
> > + */
> > + struct list_head aliases;
> > + /** Has the list caps been initialized? */
> > bool caps_initialized;
> > + /** The length of the list caps. */
> > u32 nr_caps;
> > - struct list_head caps; /* HEAD struct perf_pmu_caps -> list */
> > - struct list_head list; /* ELEM */
> > + /**
> > + * Holds the contents of files read from
> > + * <sysfs>/bus/event_source/devices/<name>/caps/. The contents are pairs
> > + * of the filename with the value of its contents, for example,
> > + * max_precise (see above) may have a value of 3.
> > + */
> > + struct list_head caps;
> > + /** Element on pmus list in pmu.c. */
> > + struct list_head list;
> > + /** Element on perf_pmu__hybrid_pmus. */
> > struct list_head hybrid_list;
> >
> > + /** Features to inhibit when events on this PMU are opened. */
> > struct {
> > + /** Disables perf_event_attr exclude_guest and exclude_host. */
> > bool exclude_guest;
> > } missing_features;
> > };
> >
> > +/** A special global PMU used for testing. */
> > extern struct perf_pmu perf_pmu__fake;
> >
> > struct perf_pmu_info {
> > @@ -71,21 +132,53 @@ struct perf_pmu_info {
> >
> > #define UNIT_MAX_LEN 31 /* max length for event unit name */
> >
> > +/**
> > + * An event either read from sysfs or builtin in pmu-events.c, created by
> > + * parsing the pmu-events json files.
> > + */
> > struct perf_pmu_alias {
> > char *name;
> > + /** Optional short description of the event. */
> > char *desc;
> > + /** Optional long description. */
> > char *long_desc;
> > + /**
> > + * Optional topic such as cache or pipeline, particularly for json
> > + * events.
> > + */
> > char *topic;
> > + /** Comma separated parameter list. */
> > char *str;
> > - struct list_head terms; /* HEAD struct parse_events_term -> list */
> > - struct list_head list; /* ELEM */
> > + /** Owned list of the original parsed parameters. */
> > + struct list_head terms;
> > + /** List element of struct perf_pmu aliases. */
> > + struct list_head list;
> > + /** Units for the event, such as bytes or cache lines. */
> > char unit[UNIT_MAX_LEN+1];
> > + /** Value to scale read counter values by. */
> > double scale;
> > + /**
> > + * Does the file
> > + * <sysfs>/bus/event_source/devices/<pmu_name>/events/<name>.per-pkg or
> > + * equivalent json value exist and have the value 1.
> > + */
> > bool per_pkg;
> > + /**
> > + * Does the file
> > + * <sysfs>/bus/event_source/devices/<pmu_name>/events/<name>.snapshot
> > + * exist and have the value 1.
> > + */
> > bool snapshot;
> > + /** Is the event hidden and so not shown in perf list by default. */
> > bool deprecated;
> > + /**
> > + * A metric expression associated with an event. Doing this makes little
> > + * sense due to scale and unit applying to both.
> > + */
> > char *metric_expr;
> > + /** A name for the metric. unit applying to both. */
> > char *metric_name;
> > + /** The name copied from struct perf_pmu. */
> > char *pmu_name;
> > };
> >
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