[PATCH v3 0/6] IMC Instrumentation Support

[Hemant Kumar]

Power 9 has In-Memory-Collection (IMC) infrastructure which contains
various Performance Monitoring Units (PMUs) at Nest level (these are
on-chip but off-core). These Nest PMU counters are handled by a Nest
IMC microcode. This microcode runs in the OCC (On-Chip Controller)
complex and its purpose is to program the nest counters, collect the
counter data and move the counter data to memory. 

The IMC infrastructure encapsulates nest (per-chip), core and thread
level counters. While the nest IMC PMUs are handled by the nest IMC
microcode, the core and thread level PMUs are handled by the Core-HPMC
engine. This patchset enables the nest IMC PMUs and is based on the
initial work done by Madhavan Srinivasan.
"Nest Instrumentation Support" : https://lists.ozlabs.org/pipermail/linuxppc-dev/2015-August/132078.html

v1 for this patchset can be found here :
https://lwn.net/Articles/705475/

Nest events:
Per-chip nest instrumentation provides various per-chip metrics
such as memory, powerbus, Xlink and Alink bandwidth.

PMU Events' Information:
OPAL obtains the Nest PMU and event information from the IMC Catalog
and passes on to the kernel via the device tree. The events' information
contains :
 - Event name
 - Event Offset
 - Event description
and, maybe :
 - Event scale
 - Event unit

Some PMUs may have a common scale and unit values for all their
supported events. For those cases, the scale and unit properties for
those events must be inherited from the PMU.

The event offset in the memory is where the counter data gets
accumulated.

The OPAL-side patches are posted upstream :
https://lists.ozlabs.org/pipermail/skiboot/2016-November/005552.html

The kernel discovers the IMC counters information in the device tree
at the "imc-counters" device node which has a compatible field
"ibm,opal-in-memory-counters".

Parsing of the Events' information:
To parse the IMC PMUs and events information, the kernel has to
discover the "imc-counters" node and walk through the pmu and event
nodes.

Here is an excerpt of the dt showing the imc-counters and mcs node:
/dts-v1/;

[...]
        imc-counters {                                                   
                imc-nest-offset = <0x320000>;
                compatible = "ibm,opal-in-memory-counters";
                imc-nest-size = <0x30000>;
                #address-cells = <0x1>;
                #size-cells = <0x1>;
                phandle = <0x10000238>;
                version-id = [00];

		mcs0 {                                                    
                        compatible = "ibm,imc-counters-chip";
                        ranges;
                        #address-cells = <0x1>;
                        #size-cells = <0x1>;
                        phandle = <0x10000279>;
			scale = "1.2207e-4";
			unit = "MiB";

			event@528 {
				event-name = "PM_MCS_UP_128B_DATA_XFER_MC0" ;
                       		desc = "Total Read Bandwidth seen on both MCS of MC0";
                                phandle = <0x1000028c>;
                                reg = <0x118 0x8>;
                        };
[...]

>From the device tree, the kernel parses the PMUs and their events'
information.

After parsing the nest IMC PMUs and their events, the PMUs and their
attributes are registered in the kernel.

Example Usage :
 # perf list

  [...]
  nest_mcs0/PM_MCS_DOWN_128B_DATA_XFER_MC0/           [Kernel PMU event]
  nest_mcs0/PM_MCS_DOWN_128B_DATA_XFER_MC0_LAST_SAMPLE/ [Kernel PMU event]
  [...]

 # perf stat -e "nest_mcs0/PM_MCS_DOWN_128B_DATA_XFER_MC0/" -a --per-socket

TODOs:
 - Add support for Core IMC.
 - Add support for thread IMC.

Comments/feedback/suggestions are welcome.

Changelog:
 v2 -> v3 :
 - Changed all references for IMA (In-Memory Accumulation) to IMC (In-Memory
   Collection).
 v1 -> v2 :
 - Account for the cases where a PMU can have a common scale and unit
   values for all its supported events (Patch 3/6).
 - Fixed a Build error (for maple_defconfig) by enabling imc_pmu.o
   only for CONFIG_PPC_POWERNV=y (Patch 4/6)
 - Read from the "event-name" property instead of "name" for an event
   node (Patch 3/6).

Cc: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Anton Blanchard <anton@xxxxxxxxx>
Cc: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
Cc: Michael Neuling <mikey@xxxxxxxxxxx>
Cc: Stewart Smith <stewart@xxxxxxxxxxxxxxxxxx>
Cc: Daniel Axtens <dja@xxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Signed-off-by: Hemant Kumar <hemant@xxxxxxxxxxxxxxxxxx>

Hemant Kumar (6):
  powerpc/powernv: Data structure and macros definitions
  powerpc/powernv: Autoload IMC device driver module
  powerpc/powernv: Detect supported IMC units and its events
  powerpc/perf: Add event attribute and group to IMC pmus
  powerpc/perf: Generic imc pmu event functions
  powerpc/perf: IMC pmu cpumask and cpu hotplug support

 arch/powerpc/include/asm/imc-pmu.h             |  74 ++++
 arch/powerpc/include/asm/opal-api.h            |   3 +-
 arch/powerpc/include/asm/opal.h                |   2 +
 arch/powerpc/perf/Makefile                     |   6 +-
 arch/powerpc/perf/imc-pmu.c                    | 383 ++++++++++++++++++++
 arch/powerpc/platforms/powernv/Makefile        |   2 +-
 arch/powerpc/platforms/powernv/opal-imc.c      | 478 +++++++++++++++++++++++++
 arch/powerpc/platforms/powernv/opal-wrappers.S |   1 +
 arch/powerpc/platforms/powernv/opal.c          |  13 +
 9 files changed, 959 insertions(+), 3 deletions(-)
 create mode 100644 arch/powerpc/include/asm/imc-pmu.h
 create mode 100644 arch/powerpc/perf/imc-pmu.c
 create mode 100644 arch/powerpc/platforms/powernv/opal-imc.c

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2.7.4