Re: [PATCH V4 0/5] powerpc, perf: BHRB based branch stack enablement on POWER8

[Michael Neuling <mikey@neuling.org>]

Anshuman,

IIRC there are new bits in the FSCR and HFSCR you need to enable for the
PMU and BRHB.  Can you please check these are enabled?

Mikey

Anshuman Khandual <khandual@linux.vnet.ibm.com> wrote:
>                 Branch History Rolling Buffer (BHRB) is a new PMU feaure in IBM
> POWER8 processor which records the branch instructions inside the execution
> pipeline. This patchset enables the basic functionality of the feature through
> generic perf branch stack sampling framework.
> 
> Sample output
> -------------
> $./perf record -b top
> $./perf report
> 
> Overhead  Command  Source Shared Object                           Source Symbol  Target Shared Object                        Target Symbol
> # ........  .......  ....................  ......................................  ....................  ...................................
> #
> 
>      7.82%      top  libc-2.11.2.so        [k] _IO_vfscanf                         libc-2.11.2.so        [k] _IO_vfscanf
>      6.17%      top  libc-2.11.2.so        [k] _IO_vfscanf                         [unknown]             [k] 00000000
>      2.37%      top  [unknown]             [k] 0xf7aafb30                          [unknown]             [k] 00000000
>      1.80%      top  [unknown]             [k] 0x0fe07978                          libc-2.11.2.so        [k] _IO_vfscanf
>      1.60%      top  libc-2.11.2.so        [k] _IO_vfscanf                         [kernel.kallsyms]     [k] .do_task_stat
>      1.20%      top  [kernel.kallsyms]     [k] .do_task_stat                       [kernel.kallsyms]     [k] .do_task_stat
>      1.02%      top  libc-2.11.2.so        [k] vfprintf                            libc-2.11.2.so        [k] vfprintf
>      0.92%      top  top                   [k] _init                               [unknown]             [k] 0x0fe037f4
> 
> Changes in V2
> --------------
> - Added copyright messages to the newly created files
> - Modified couple of commit messages
> 
> Changes in V3
> -------------
> - Incorporated review comments from Segher https://lkml.org/lkml/2013/4/16/350
> - Worked on a solution for review comment from Michael Ellerman https://lkml.org/lkml/2013/4/17/548
> 	- Could not move updated cpu_hw_events structure from core-book3s.c file into perf_event_server.h
>           Because perf_event_server.h is pulled in first inside linux/perf_event.h before the definition of
>           perf_branch_entry structure. Thats the reason why perf_branch_entry definition is not available
>           inside perf_event_server.h where we define the array inside cpu_hw_events structure.
> 
> 	- Finally have pulled in the code from perf_event_bhrb.c into core-book3s.c
> 
> - Improved documentation for the patchset
> 
> Changes in V4
> -------------
> - Incorporated review comments on V3 regarding new instruction encoding
> 
> Anshuman Khandual (5):
>   powerpc, perf: Add new BHRB related instructions for POWER8
>   powerpc, perf: Add basic assembly code to read BHRB entries on POWER8
>   powerpc, perf: Add new BHRB related generic functions, data and flags
>   powerpc, perf: Define BHRB generic functions, data and flags for POWER8
>   powerpc, perf: Enable branch stack sampling framework
> 
>  arch/powerpc/include/asm/perf_event_server.h |   7 ++
>  arch/powerpc/include/asm/ppc-opcode.h        |   8 ++
>  arch/powerpc/perf/Makefile                   |   2 +-
>  arch/powerpc/perf/bhrb.S                     |  44 +++++++
>  arch/powerpc/perf/core-book3s.c              | 167 ++++++++++++++++++++++++++-
>  arch/powerpc/perf/power8-pmu.c               |  57 ++++++++-
>  6 files changed, 280 insertions(+), 5 deletions(-)
>  create mode 100644 arch/powerpc/perf/bhrb.S
> 
> -- 
> 1.7.11.7
>