Messages in this thread | | | From | Ian Rogers <> | Date | Thu, 19 May 2022 14:36:56 -0700 | Subject | Re: [PATCH V2 1/2] powerpc/perf: Add support for caps under sysfs in powerpc |
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On Thu, May 19, 2022 at 4:29 AM Athira Rajeev <atrajeev@linux.vnet.ibm.com> wrote: > > > On 19-May-2022, at 10:12 AM, Ian Rogers <irogers@google.com> wrote: > > > > On Wed, May 18, 2022 at 1:55 AM Athira Rajeev > > <atrajeev@linux.vnet.ibm.com> wrote: > >> > >> Add caps support under "/sys/bus/event_source/devices/<pmu>/" > >> for powerpc. This directory can be used to expose some of the > >> specific features that powerpc PMU supports to the user. > >> Example: pmu_name. The name of PMU registered will depend on > >> platform, say power9 or power10 or it could be Generic Compat > >> PMU. > >> > >> Currently the only way to know which is the registered > >> PMU is from the dmesg logs. But clearing the dmesg will make it > >> difficult to know exact PMU backend used. And even extracting > >> from dmesg will be complicated, as we need to parse the dmesg > >> logs and add filters for pmu name. Whereas by exposing it via > >> caps will make it easy as we just need to directly read it from > >> the sysfs. > > > > For ARM and x86 in the perf tool this is normally done through a cpuid > > like function, is there a reason to differ on Power? > > > > Thanks, > > Ian > > Hi Ian, > > Thanks for review. The information from cpuid or cpuinfo will provide > us the information of the platform/model/machine etc. In case of powerpc, > we have one case where, though platform points to specific generation of the > processor, say power9 or power10, the registered PMU could point to > different one. To be specific, this is named as Generic Compat PMU which > is a fallback PMU. This gets registered when the distro doesn't have support > for platform specific PMU. In that case distro will have a Generic > Compat PMU registered which supports basic features for performance monitoring. > This information can't be fetched from the cpuid data since that will point > to current platform. > > So the pmu_name exposed via "caps" will be useful to detect the PMU > registered and also we target to use this information in some of our > selftests.
Thanks, I've no problem with the change. Do we need to do a similar discovery in the perf tool on old kernels? Perhaps then this information could be exposed in the perf list command for self tests.
Thanks, Ian
> Thanks > Athira > > > >> Add a caps directory to /sys/bus/event_source/devices/cpu/ > >> for power8, power9, power10 and generic compat PMU in respective > >> PMU driver code. Update the pmu_name file under caps folder > >> in core-book3s using "attr_update". > >> > >> The information exposed currently: > >> - pmu_name : Underlying PMU name from the driver > >> > >> Example result with power9 pmu: > >> > >> # ls /sys/bus/event_source/devices/cpu/caps > >> pmu_name > >> > >> # cat /sys/bus/event_source/devices/cpu/caps/pmu_name > >> POWER9 > >> > >> Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com> > >> --- > >> Changelog: > >> v1 -> v2: > >> Move the show function as generic in core-book3s > >> and update show function using sysfs_emit and ppmu->name > >> Added Documention for this ABI in patch 2. > >> Notes: The caps directory is implemented in PMU for other > >> architectures already. Reference commit for x86: > >> commit b00233b53065 ("perf/x86: Export some PMU attributes in caps/ directory") > >> > >> arch/powerpc/perf/core-book3s.c | 31 ++++++++++++++++++++++++++ > >> arch/powerpc/perf/generic-compat-pmu.c | 10 +++++++++ > >> arch/powerpc/perf/power10-pmu.c | 10 +++++++++ > >> arch/powerpc/perf/power8-pmu.c | 10 +++++++++ > >> arch/powerpc/perf/power9-pmu.c | 10 +++++++++ > >> 5 files changed, 71 insertions(+) > >> > >> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c > >> index b5b42cf0a703..a208f502a80b 100644 > >> --- a/arch/powerpc/perf/core-book3s.c > >> +++ b/arch/powerpc/perf/core-book3s.c > >> @@ -2488,6 +2488,33 @@ static int power_pmu_prepare_cpu(unsigned int cpu) > >> return 0; > >> } > >> > >> +static ssize_t pmu_name_show(struct device *cdev, > >> + struct device_attribute *attr, > >> + char *buf) > >> +{ > >> + if (ppmu) > >> + return sysfs_emit(buf, "%s\n", ppmu->name); > >> + > >> + return 0; > >> +} > >> + > >> +static DEVICE_ATTR_RO(pmu_name); > >> + > >> +static struct attribute *pmu_caps_attrs[] = { > >> + &dev_attr_pmu_name.attr, > >> + NULL > >> +}; > >> + > >> +static const struct attribute_group pmu_caps_group = { > >> + .name = "caps", > >> + .attrs = pmu_caps_attrs, > >> +}; > >> + > >> +static const struct attribute_group *pmu_caps_groups[] = { > >> + &pmu_caps_group, > >> + NULL, > >> +}; > >> + > >> int __init register_power_pmu(struct power_pmu *pmu) > >> { > >> if (ppmu) > >> @@ -2498,6 +2525,10 @@ int __init register_power_pmu(struct power_pmu *pmu) > >> pmu->name); > >> > >> power_pmu.attr_groups = ppmu->attr_groups; > >> + > >> + if (ppmu->flags & PPMU_ARCH_207S) > >> + power_pmu.attr_update = pmu_caps_groups; > >> + > >> power_pmu.capabilities |= (ppmu->capabilities & PERF_PMU_CAP_EXTENDED_REGS); > >> > >> #ifdef MSR_HV > >> diff --git a/arch/powerpc/perf/generic-compat-pmu.c b/arch/powerpc/perf/generic-compat-pmu.c > >> index f3db88aee4dd..817c69863038 100644 > >> --- a/arch/powerpc/perf/generic-compat-pmu.c > >> +++ b/arch/powerpc/perf/generic-compat-pmu.c > >> @@ -151,9 +151,19 @@ static const struct attribute_group generic_compat_pmu_format_group = { > >> .attrs = generic_compat_pmu_format_attr, > >> }; > >> > >> +static struct attribute *generic_compat_pmu_caps_attrs[] = { > >> + NULL > >> +}; > >> + > >> +static struct attribute_group generic_compat_pmu_caps_group = { > >> + .name = "caps", > >> + .attrs = generic_compat_pmu_caps_attrs, > >> +}; > >> + > >> static const struct attribute_group *generic_compat_pmu_attr_groups[] = { > >> &generic_compat_pmu_format_group, > >> &generic_compat_pmu_events_group, > >> + &generic_compat_pmu_caps_group, > >> NULL, > >> }; > >> > >> diff --git a/arch/powerpc/perf/power10-pmu.c b/arch/powerpc/perf/power10-pmu.c > >> index c6d51e7093cf..d1adcd9f52e2 100644 > >> --- a/arch/powerpc/perf/power10-pmu.c > >> +++ b/arch/powerpc/perf/power10-pmu.c > >> @@ -258,6 +258,15 @@ static const struct attribute_group power10_pmu_format_group = { > >> .attrs = power10_pmu_format_attr, > >> }; > >> > >> +static struct attribute *power10_pmu_caps_attrs[] = { > >> + NULL > >> +}; > >> + > >> +static struct attribute_group power10_pmu_caps_group = { > >> + .name = "caps", > >> + .attrs = power10_pmu_caps_attrs, > >> +}; > >> + > >> static const struct attribute_group *power10_pmu_attr_groups_dd1[] = { > >> &power10_pmu_format_group, > >> &power10_pmu_events_group_dd1, > >> @@ -267,6 +276,7 @@ static const struct attribute_group *power10_pmu_attr_groups_dd1[] = { > >> static const struct attribute_group *power10_pmu_attr_groups[] = { > >> &power10_pmu_format_group, > >> &power10_pmu_events_group, > >> + &power10_pmu_caps_group, > >> NULL, > >> }; > >> > >> diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c > >> index e37b1e714d2b..2518f5375d4a 100644 > >> --- a/arch/powerpc/perf/power8-pmu.c > >> +++ b/arch/powerpc/perf/power8-pmu.c > >> @@ -187,9 +187,19 @@ static const struct attribute_group power8_pmu_events_group = { > >> .attrs = power8_events_attr, > >> }; > >> > >> +static struct attribute *power8_pmu_caps_attrs[] = { > >> + NULL > >> +}; > >> + > >> +static struct attribute_group power8_pmu_caps_group = { > >> + .name = "caps", > >> + .attrs = power8_pmu_caps_attrs, > >> +}; > >> + > >> static const struct attribute_group *power8_pmu_attr_groups[] = { > >> &isa207_pmu_format_group, > >> &power8_pmu_events_group, > >> + &power8_pmu_caps_group, > >> NULL, > >> }; > >> > >> diff --git a/arch/powerpc/perf/power9-pmu.c b/arch/powerpc/perf/power9-pmu.c > >> index c393e837648e..5c654ce1a417 100644 > >> --- a/arch/powerpc/perf/power9-pmu.c > >> +++ b/arch/powerpc/perf/power9-pmu.c > >> @@ -258,9 +258,19 @@ static const struct attribute_group power9_pmu_format_group = { > >> .attrs = power9_pmu_format_attr, > >> }; > >> > >> +static struct attribute *power9_pmu_caps_attrs[] = { > >> + NULL > >> +}; > >> + > >> +static struct attribute_group power9_pmu_caps_group = { > >> + .name = "caps", > >> + .attrs = power9_pmu_caps_attrs, > >> +}; > >> + > >> static const struct attribute_group *power9_pmu_attr_groups[] = { > >> &power9_pmu_format_group, > >> &power9_pmu_events_group, > >> + &power9_pmu_caps_group, > >> NULL, > >> }; > >> > >> -- > >> 2.31.1 >
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