[PATCH 08/11] arm64: pmu: Provide cpumask attribute for PMU

[Mark Rutland]

Hi Jeremy,

Apologies for the late reply on this.

On Tue, Jun 21, 2016 at 12:11:46PM -0500, Jeremy Linton wrote:
> With heterogeneous PMUs its helpful to know which PMUs are bound
> to each CPU. Provide that information with a cpumask sysfs entry
> similar to other PMUs.

Have you tested trying to stat on a particular PMU? e.g.

$ perf stat -e armv8_cortex_a53/cpu_cycles/ ls

I found that the presence of a cpumask file would cause (at least some
versions) of perf-stat to hang, and was holding off adding a cpumask
until we had a solution to that.

See [1,2] for more details on that.

> Signed-off-by: Jeremy Linton <jeremy.linton at arm.com>
> ---
>  arch/arm64/kernel/perf_event.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)

This should be generic across the arm-pmu code, and so should live under
drivers/perf/.

Thanks,
Mark.

[1] http://lkml.kernel.org/r/1467907474-3290-1-git-send-email-mark.rutland@arm.com
[2] http://lkml.kernel.org/r/1467907474-3290-2-git-send-email-mark.rutland@arm.com

> diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
> index 356fa6c..dae73ea 100644
> --- a/arch/arm64/kernel/perf_event.c
> +++ b/arch/arm64/kernel/perf_event.c
> @@ -533,6 +533,26 @@ static struct attribute_group armv8_pmuv3_events_attr_group = {
>  
>  PMU_FORMAT_ATTR(event, "config:0-9");
>  
> +static ssize_t
> +cpumask_show(struct device *dev, struct device_attribute *attr, char *page)
> +{
> +	struct pmu *pmu = dev_get_drvdata(dev);
> +	struct arm_pmu *cpu_pmu = container_of(pmu, struct arm_pmu, pmu);
> +
> +	return cpumap_print_to_pagebuf(true, page, &cpu_pmu->supported_cpus);
> +}
> +static DEVICE_ATTR_RO(cpumask);
> +
> +static struct attribute *armv8_pmuv3_attrs[] = {
> +	 &dev_attr_cpumask.attr,
> +	 NULL,
> +};
> +
> +static struct attribute_group armv8_pmuv3_attr_group = {
> +	.attrs = armv8_pmuv3_attrs,
> +};
> +
> +
>  static struct attribute *armv8_pmuv3_format_attrs[] = {
>  	&format_attr_event.attr,
>  	NULL,
> @@ -544,6 +564,7 @@ static struct attribute_group armv8_pmuv3_format_attr_group = {
>  };
>  
>  static const struct attribute_group *armv8_pmuv3_attr_groups[] = {
> +	&armv8_pmuv3_attr_group,
>  	&armv8_pmuv3_events_attr_group,
>  	&armv8_pmuv3_format_attr_group,
>  	NULL,
> -- 
> 2.5.5
>