Re: [PATCH v8 1/3] perf x86: Infrastructure for exposing an Uncore unit to PMON mapping

["Sudarikov, Roman" <roman.sudarikov@linux.intel.com>]

On 20.03.2020 10:31, roman.sudarikov@linux.intel.com wrote:
> From: Roman Sudarikov <roman.sudarikov@linux.intel.com>
>
> Intel® Xeon® Scalable processor family (code name Skylake-SP) makes
> significant changes in the integrated I/O (IIO) architecture. The new
> solution introduces IIO stacks which are responsible for managing traffic
> between the PCIe domain and the Mesh domain. Each IIO stack has its own
> PMON block and can handle either DMI port, x16 PCIe root port, MCP-Link
> or various built-in accelerators. IIO PMON blocks allow concurrent
> monitoring of I/O flows up to 4 x4 bifurcation within each IIO stack.
>
> Software is supposed to program required perf counters within each IIO
> stack and gather performance data. The tricky thing here is that IIO PMON
> reports data per IIO stack but users have no idea what IIO stacks are -
> they only know devices which are connected to the platform.
>
> Understanding IIO stack concept to find which IIO stack that particular
> IO device is connected to, or to identify an IIO PMON block to program
> for monitoring specific IIO stack assumes a lot of implicit knowledge
> about given Intel server platform architecture.
>
> Usage example:
>      ls /sys/devices/uncore_<type>_<pmu_idx>/die*
>
> Each Uncore unit type, by its nature, can be mapped to its own context,
> for example:
> 1. CHA - each uncore_cha_<pmu_idx> is assigned to manage a distinct slice
>     of LLC capacity;
> 2. UPI - each uncore_upi_<pmu_idx> is assigned to manage one link of Intel
>     UPI Subsystem;
> 3. IIO - each uncore_iio_<pmu_idx> is assigned to manage one stack of the
>     IIO module;
> 4. IMC - each uncore_imc_<pmu_idx> is assigned to manage one channel of
>     Memory Controller.
>
> Implementation details:
> Optional callbacks added to struct intel_uncore_type to discover and map
> Uncore units to PMONs:
>      int (*set_mapping)(struct intel_uncore_type *type)
>      void (*cleanup_mapping)(struct intel_uncore_type *type)
>
> Details of IIO Uncore unit mapping to IIO PMON:
> Each IIO stack is either DMI port, x16 PCIe root port, MCP-Link or various
> built-in accelerators. For Uncore IIO Unit type, the mapping file
> holds bus numbers of devices, which can be monitored by that IIO PMON block
> on each die.
>
> Co-developed-by: Alexander Antonov <alexander.antonov@intel.com>
> Signed-off-by: Alexander Antonov <alexander.antonov@intel.com>
> Signed-off-by: Roman Sudarikov <roman.sudarikov@linux.intel.com>
> Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
> ---
>   arch/x86/events/intel/uncore.c | 8 ++++++++
>   arch/x86/events/intel/uncore.h | 6 ++++++
>   2 files changed, 14 insertions(+)
>
> diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
> index 86467f85c383..fb693608c223 100644
> --- a/arch/x86/events/intel/uncore.c
> +++ b/arch/x86/events/intel/uncore.c
> @@ -843,10 +843,12 @@ static int uncore_pmu_register(struct intel_uncore_pmu *pmu)
>   			.read		= uncore_pmu_event_read,
>   			.module		= THIS_MODULE,
>   			.capabilities	= PERF_PMU_CAP_NO_EXCLUDE,
> +			.attr_update	= pmu->type->attr_update,
>   		};
>   	} else {
>   		pmu->pmu = *pmu->type->pmu;
>   		pmu->pmu.attr_groups = pmu->type->attr_groups;
> +		pmu->pmu.attr_update = pmu->type->attr_update;
>   	}
>   
>   	if (pmu->type->num_boxes == 1) {
> @@ -887,6 +889,9 @@ static void uncore_type_exit(struct intel_uncore_type *type)
>   	struct intel_uncore_pmu *pmu = type->pmus;
>   	int i;
>   
> +	if (type->cleanup_mapping)
> +		type->cleanup_mapping(type);
> +
>   	if (pmu) {
>   		for (i = 0; i < type->num_boxes; i++, pmu++) {
>   			uncore_pmu_unregister(pmu);
> @@ -954,6 +959,9 @@ static int __init uncore_type_init(struct intel_uncore_type *type, bool setid)
>   
>   	type->pmu_group = &uncore_pmu_attr_group;
>   
> +	if (type->set_mapping)
> +		type->set_mapping(type);
> +
>   	return 0;
>   
>   err:
> diff --git a/arch/x86/events/intel/uncore.h b/arch/x86/events/intel/uncore.h
> index bbfdaa720b45..d41f8874adc5 100644
> --- a/arch/x86/events/intel/uncore.h
> +++ b/arch/x86/events/intel/uncore.h
> @@ -72,7 +72,13 @@ struct intel_uncore_type {
>   	struct uncore_event_desc *event_descs;
>   	struct freerunning_counters *freerunning;
>   	const struct attribute_group *attr_groups[4];
> +	const struct attribute_group **attr_update;
>   	struct pmu *pmu; /* for custom pmu ops */
> +	/* PMON's topologies */
> +	u64 *topology;
> +	/* mapping Uncore units to PMON ranges */
> +	int (*set_mapping)(struct intel_uncore_type *type);
> +	void (*cleanup_mapping)(struct intel_uncore_type *type);
>   };
>   
>   #define pmu_group attr_groups[0]
Hello Peter,
are you waiting for some further review/ack on this, or is it just in your
pending review queue?

Sorry for bothering you several times, but the feature will add value to 
users.

Thanks,
Roman