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

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