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    SubjectRe: [PATCH v1 05/23] perf pmu: Remove perf_pmu__hybrid_mounted
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    On 2023-05-22 10:06 a.m., Ian Rogers wrote:
    > On Mon, May 22, 2023 at 4:55 AM Liang, Kan <kan.liang@linux.intel.com> wrote:
    >>
    >>
    >>
    >> On 2023-05-22 1:21 a.m., Ian Rogers wrote:
    >>> On Sun, May 21, 2023 at 12:23 PM Liang, Kan <kan.liang@linux.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.
    >>
    >> But if we add a new core type "cpu_whatever" later, we have to hardcode
    >> the new name to the perf tool, right? Users have to update the perf tool
    >> for the new platforms, otherwise I think the new type will be treated as
    >> an uncore PMU.
    >>
    >> Since the hybrid is Intel only, I think it may be better move the
    >> is_pmu_hybrid() to X86 specifc code. For the Intel only code, we already
    >> have a naming rule for the hybrid name, "cpu_$". So we don't need to
    >> update the tool for every new CPU type.
    >>
    >> Thanks,
    >> Kan
    >
    > I don't disagree, but fixing all uses of is_pmu_hybrid and similarly
    > perf_pmus__has_hybrid is going to add yet more to a moderately long
    > patch series. I think in most cases is_pmu_hybrid can be replaced by a
    > core oriented alternative. For example, in pmu.c there is
    > perf_pmu__auto_merge_stats that normally returns true that we want to
    > merge counts for uncore or non-hybrid PMUs. For hybrid it returns
    > false so that cpu_atom and cpu_core counts aren't merged. A core
    > oriented alternative would be to return false if the PMU is core and
    > the number of core PMUs is >1 - this also avoids any hard coding of
    > PMU names and assuming >1 core PMU means they all begin with "cpu_".

    I'm OK with the alternative method.

    >
    > The scope of fixing the remaining is_pmu_hybrid and perf_pmus__has_hybrid is:
    I don't think we need to modify each places listed below.
    We just need to update is_pmu_hybrid() and perf_pmus__has_hybrid(). And
    probably use is_pmu_hybrid() to replace perf_pmu__skip_empty_cpus().
    I don't think we need to change the interface.

    It should not be a big patch.

    Is there anything I missed?

    Thanks,
    Kan
    > ```
    > $ grep -rn perf_pmus__has_hybrid tools/perf
    > tools/perf/util/header.c:1592: if (perf_pmus__has_hybrid()) {
    > tools/perf/util/mem-events.c:132: if (!perf_pmus__has_hybrid()) {
    > tools/perf/util/mem-events.c:199: if (!perf_pmus__has_hybrid()) {
    > tools/perf/util/evsel.c:3139: if (!perf_pmus__has_hybrid())
    > tools/perf/util/pmus.h:21:bool perf_pmus__has_hybrid(void);
    > tools/perf/util/stat-display.c:684: if (!perf_pmus__has_hybrid())
    > tools/perf/util/metricgroup.c:277: bool all_pmus = !strcmp(pmu,
    > "all") || !perf_pmus__has_hybrid() || !is_pmu_hybrid(pmu);
    > tools/perf/util/pmus.c:474:bool perf_pmus__has_hybrid(void)
    > tools/perf/util/cputopo.c:477: if (!perf_pmus__has_hybrid())
    > tools/perf/tests/attr.c:188: if (perf_pmus__has_hybrid())
    > tools/perf/tests/topology.c:44: if (!perf_pmus__has_hybrid()) {
    > tools/perf/tests/parse-metric.c:306: if (!perf_pmus__has_hybrid()) {
    > tools/perf/tests/switch-tracking.c:378: if (perf_pmus__has_hybrid()) {
    > tools/perf/builtin-record.c:1297: perf_pmus__has_hybrid()) {
    > tools/perf/builtin-record.c:2196: if (!perf_pmus__has_hybrid())
    > tools/perf/builtin-record.c:4196: rec->opts.target.hybrid =
    > perf_pmus__has_hybrid();
    > tools/perf/builtin-stat.c:2463: target.hybrid = perf_pmus__has_hybrid();
    > tools/perf/arch/x86/util/perf_regs.c:295: if (perf_pmus__has_hybrid()) {
    > tools/perf/arch/x86/util/evlist.c:21: if (!perf_pmus__has_hybrid())
    > tools/perf/arch/x86/tests/hybrid.c:284: if (!perf_pmus__has_hybrid())
    >
    > $ grep -rn is_pmu_hybrid tools/perf
    > tools/perf/util/pmu.c:1433:bool is_pmu_hybrid(const char *name)
    > tools/perf/util/pmu.c:1445: return !is_pmu_hybrid(pmu->name);
    > tools/perf/util/pmu.h:224:bool is_pmu_hybrid(const char *name);
    > tools/perf/util/metricgroup.c:277: bool all_pmus = !strcmp(pmu,
    > "all") || !perf_pmus__
    > has_hybrid() || !is_pmu_hybrid(pmu);
    > tools/perf/util/pmus.c:482: if (is_pmu_hybrid(pmu->name)) {
    > ```
    >
    > So, I think it makes sense to do it as a follow up.
    >
    > Thanks,
    > Ian
    >
    >>>
    >>> 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@google.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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