Message-ID: <CAP-5=fU3OYNsjaJhLq_8tJXZKFARCTqrg3CEr64-3rAm_kTx+A@mail.gmail.com>
Date:   Sun, 21 May 2023 22:21:57 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        John Garry <john.g.garry@...cle.com>,
        Will Deacon <will@...nel.org>,
        James Clark <james.clark@....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>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Jing Zhang <renyu.zj@...ux.alibaba.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Ming Wang <wangming01@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        Sandipan Das <sandipan.das@....com>,
        Dmitrii Dolgov <9erthalion6@...il.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Ali Saidi <alisaidi@...zon.com>, Rob Herring <robh@...nel.org>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Kang Minchul <tegongkang@...il.com>,
        linux-kernel@...r.kernel.org, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v1 05/23] perf pmu: Remove perf_pmu__hybrid_mounted

On Sun, May 21, 2023 at 12:23 PM Liang, Kan <kan.liang@...ux.intel.com> wrote:
>
>
>
> On 2023-05-17 10:57 a.m., Ian Rogers wrote:
> > perf_pmu__hybrid_mounted is used to detect whether cpu_core or
> > cpu_atom
>
> Currently, there are only two CPU types for a hybrid machine, core and
> atom. But there may be more CPU types added later. Please see the CPUID
> 1AH EAX enumeration in SDM VOL2. It has several reserved encodings for
> CPU types. It's better not using the hardcode cpu_core/cpu_atom to
> replace the perf_pmu__hybrid_mounted().
>
> Thanks,
> Kan

This is covered by later patches. Specifically patches like:
patch 7: perf pmu: Add is_core to pmu
patch 20: Split pmus list into core and uncore

Ultimately in pmus.h we have two scan routines, one for all PMUs and
one for core PMUs. For everything except hybrid (and the name varies a
bit on ARM) the core scan only scans "cpu", on hybrid it scans
"cpu_atom" and "cpu_core".  The determination of core vs uncore is
done without using the name, so can support >2 hybrid PMUs. At this
point in the patch series I'm trying to simplify everything so that I
can then build the pmus interface.

Thanks,
Ian

> > is mounted with a non-empty cpus file by
> > pmu_lookup. pmu_lookup will attempt to read the cpus file too and so
> > the check can be folded into this.
> >
> > Checking hybrid_mounted in pmu_is_uncore is redundant as the next
> > cpumask read will fail returning false.
> >
> > Reduce the scope of perf_pmu__find_hybrid_pmu by making it static.
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> >  tools/perf/util/pmu-hybrid.c | 15 +--------------
> >  tools/perf/util/pmu-hybrid.h |  3 ---
> >  tools/perf/util/pmu.c        | 26 ++++++++++++++------------
> >  3 files changed, 15 insertions(+), 29 deletions(-)
> >
> > diff --git a/tools/perf/util/pmu-hybrid.c b/tools/perf/util/pmu-hybrid.c
> > index bc4cb0738c35..7fe943dd3217 100644
> > --- a/tools/perf/util/pmu-hybrid.c
> > +++ b/tools/perf/util/pmu-hybrid.c
> > @@ -18,20 +18,7 @@
> >
> >  LIST_HEAD(perf_pmu__hybrid_pmus);
> >
> > -bool perf_pmu__hybrid_mounted(const char *name)
> > -{
> > -     int cpu;
> > -     char pmu_name[PATH_MAX];
> > -     struct perf_pmu pmu = {.name = pmu_name};
> > -
> > -     if (strncmp(name, "cpu_", 4))
> > -             return false;
> > -
> > -     strlcpy(pmu_name, name, sizeof(pmu_name));
> > -     return perf_pmu__scan_file(&pmu, "cpus", "%u", &cpu) > 0;
> > -}
> > -
> > -struct perf_pmu *perf_pmu__find_hybrid_pmu(const char *name)
> > +static struct perf_pmu *perf_pmu__find_hybrid_pmu(const char *name)
> >  {
> >       struct perf_pmu *pmu;
> >
> > diff --git a/tools/perf/util/pmu-hybrid.h b/tools/perf/util/pmu-hybrid.h
> > index 206b94931531..8dbcae935020 100644
> > --- a/tools/perf/util/pmu-hybrid.h
> > +++ b/tools/perf/util/pmu-hybrid.h
> > @@ -13,9 +13,6 @@ extern struct list_head perf_pmu__hybrid_pmus;
> >  #define perf_pmu__for_each_hybrid_pmu(pmu)   \
> >       list_for_each_entry(pmu, &perf_pmu__hybrid_pmus, hybrid_list)
> >
> > -bool perf_pmu__hybrid_mounted(const char *name);
> > -
> > -struct perf_pmu *perf_pmu__find_hybrid_pmu(const char *name);
> >  bool perf_pmu__is_hybrid(const char *name);
> >
> >  static inline int perf_pmu__hybrid_pmu_num(void)
> > diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> > index 1e0be23d4dd7..729b1f166f80 100644
> > --- a/tools/perf/util/pmu.c
> > +++ b/tools/perf/util/pmu.c
> > @@ -617,9 +617,6 @@ static bool pmu_is_uncore(int dirfd, const char *name)
> >  {
> >       int fd;
> >
> > -     if (perf_pmu__hybrid_mounted(name))
> > -             return false;
> > -
> >       fd = perf_pmu__pathname_fd(dirfd, name, "cpumask", O_PATH);
> >       if (fd < 0)
> >               return false;
> > @@ -898,6 +895,16 @@ static int pmu_max_precise(int dirfd, struct perf_pmu *pmu)
> >       return max_precise;
> >  }
> >
> > +/**
> > + * perf_pmu__skip_empty_cpus() - should pmu_lookup skip the named PMU if the
> > + *      cpus or cpumask file isn't present?
> > + * @name: Name of PMU.
> > + */
> > +static bool perf_pmu__skip_empty_cpus(const char *name)
> > +{
> > +     return !strcmp(name, "cpu_core") || !strcmp(name, "cpu_atom");
> > +}
> > +
> >  static struct perf_pmu *pmu_lookup(int dirfd, const char *lookup_name)
> >  {
> >       struct perf_pmu *pmu;
> > @@ -905,15 +912,8 @@ static struct perf_pmu *pmu_lookup(int dirfd, const char *lookup_name)
> >       LIST_HEAD(aliases);
> >       __u32 type;
> >       char *name = pmu_find_real_name(lookup_name);
> > -     bool is_hybrid = perf_pmu__hybrid_mounted(name);
> >       char *alias_name;
> >
> > -     /*
> > -      * Check pmu name for hybrid and the pmu may be invalid in sysfs
> > -      */
> > -     if (!strncmp(name, "cpu_", 4) && !is_hybrid)
> > -             return NULL;
> > -
> >       /*
> >        * The pmu data we store & need consists of the pmu
> >        * type value and format definitions. Load both right
> > @@ -933,8 +933,10 @@ static struct perf_pmu *pmu_lookup(int dirfd, const char *lookup_name)
> >               return NULL;
> >
> >       pmu->cpus = pmu_cpumask(dirfd, name);
> > -     pmu->name = strdup(name);
> > +     if (!pmu->cpus && perf_pmu__skip_empty_cpus(name))
> > +             goto err;
> >
> > +     pmu->name = strdup(name);
> >       if (!pmu->name)
> >               goto err;
> >
> > @@ -964,7 +966,7 @@ static struct perf_pmu *pmu_lookup(int dirfd, const char *lookup_name)
> >       list_splice(&aliases, &pmu->aliases);
> >       list_add_tail(&pmu->list, &pmus);
> >
> > -     if (is_hybrid)
> > +     if (!strcmp(name, "cpu_core") || !strcmp(name, "cpu_atom"))
> >               list_add_tail(&pmu->hybrid_list, &perf_pmu__hybrid_pmus);
> >       else
> >               INIT_LIST_HEAD(&pmu->hybrid_list);

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