[RFC v3 0/4] Add perf interface to expose nvdimm

[Kajol Jain]

Patchset adds performance stats reporting support for nvdimm.
Added interface includes support for pmu register/unregister
functions. A structure is added called nvdimm_pmu to be used for
adding arch/platform specific data such as supported events and pmu
event functions like event_init/add/read/del.
User could use the standard perf tool to access perf
events exposed via pmu.

Added implementation to expose IBM pseries platform nmem*
device performance stats using this interface.

Result from power9 pseries lpar with 2 nvdimm device:
command:# perf list nmem
  nmem0/cchrhcnt/                                    [Kernel PMU event]
  nmem0/cchwhcnt/                                    [Kernel PMU event]
  nmem0/critrscu/                                    [Kernel PMU event]
  nmem0/ctlresct/                                    [Kernel PMU event]
  nmem0/ctlrestm/                                    [Kernel PMU event]
  nmem0/fastwcnt/                                    [Kernel PMU event]
  nmem0/hostlcnt/                                    [Kernel PMU event]
  nmem0/hostldur/                                    [Kernel PMU event]
  nmem0/hostscnt/                                    [Kernel PMU event]
  nmem0/hostsdur/                                    [Kernel PMU event]
  nmem0/medrcnt/                                     [Kernel PMU event]
  nmem0/medrdur/                                     [Kernel PMU event]
  nmem0/medwcnt/                                     [Kernel PMU event]
  nmem0/medwdur/                                     [Kernel PMU event]
  nmem0/memlife/                                     [Kernel PMU event]
  nmem0/noopstat/                                    [Kernel PMU event]
  nmem0/ponsecs/                                     [Kernel PMU event]
  nmem1/cchrhcnt/                                    [Kernel PMU event]
  nmem1/cchwhcnt/                                    [Kernel PMU event]
  nmem1/critrscu/                                    [Kernel PMU event]
  ...
  nmem1/noopstat/                                    [Kernel PMU event]
  nmem1/ponsecs/                                     [Kernel PMU event]

Patch1:
        Introduces the nvdimm_pmu structure
Patch2:
	Adds common interface to add arch/platform specific data
	includes supported events, pmu event functions. It also
	adds code for cpu hotplug support.
Patch3:
        Add code in arch/powerpc/platform/pseries/papr_scm.c to expose
        nmem* pmu. It fills in the nvdimm_pmu structure with event attrs
        and event functions and then registers the pmu by adding
        callbacks to register_nvdimm_pmu.
Patch4:
        Sysfs documentation patch

Changelog
---
v2 -> v3
- Link to the RFC v2 patchset : https://lkml.org/lkml/2021/5/25/591

- Moved hotplug code changes from papr_scm code to generic interface
  with required functionality as suggested by Peter Zijlstra

- Changed function parameter of unregister_nvdimm_pmu function from
  struct pmu to struct nvdimm_pmu.

- Now cpumask will get updated based on numa node of corresponding nvdimm
  device as suggested by Peter Zijlstra.

- Some optimizations/fixes from previous RFC code

v1 -> v2
- Link to the RFC v1 patchset : https://lkml.org/lkml/2021/5/12/2747

- Removed intermediate functions nvdimm_pmu_read/nvdimm_pmu_add/
  nvdimm_pmu_del/nvdimm_pmu_event_init and directly assigned
  platfrom specific routines. Also add check for any NULL functions.
  Suggested by: Peter Zijlstra

- Add macros for event attribute array index which can be used to
  assign dynamically allocated attr_groups.

- New function 'nvdimm_pmu_mem_free' is added to free dynamic
  memory allocated for attr_groups in papr_scm.c

- PMU register call moved from papr_scm_nvdimm_init() to papr_scm_probe()

- Move addition of cpu/node/cpuhp_state attributes in struct nvdimm_pmu
  to patch 4 where cpu hotplug code added

- Removed device attribute from the attribute list of
  add/del/read/event_init functions in nvdimm_pmu structure
  as we need to assign them directly to pmu structure.

---

Kajol Jain (4):
  drivers/nvdimm: Add nvdimm pmu structure
  drivers/nvdimm: Add perf interface to expose nvdimm performance stats
  powerpc/papr_scm: Add perf interface support
  powerpc/papr_scm: Document papr_scm sysfs event format entries

 Documentation/ABI/testing/sysfs-bus-papr-pmem |  31 ++
 arch/powerpc/include/asm/device.h             |   5 +
 arch/powerpc/platforms/pseries/papr_scm.c     | 358 ++++++++++++++++++
 drivers/nvdimm/Makefile                       |   1 +
 drivers/nvdimm/nd_perf.c                      | 195 ++++++++++
 include/linux/nd.h                            |  42 ++
 6 files changed, 632 insertions(+)
 create mode 100644 drivers/nvdimm/nd_perf.c

-- 
2.27.0