[PATCH V2 0/9] Add data type profiling support for powerpc

Athira Rajeev atrajeev at linux.vnet.ibm.com
Mon May 13 17:32:10 AEST 2024



> On 7 May 2024, at 10:09 AM, Namhyung Kim <namhyung at kernel.org> wrote:
> 
> Hello,
> 
> On Mon, May 6, 2024 at 5:19 AM Athira Rajeev
> <atrajeev at linux.vnet.ibm.com> wrote:
>> 
>> The patchset from Namhyung added support for data type profiling
>> in perf tool. This enabled support to associate PMU samples to data
>> types they refer using DWARF debug information. With the upstream
>> perf, currently it possible to run perf report or perf annotate to
>> view the data type information on x86.
>> 
>> Initial patchset posted here had changes need to enable data type
>> profiling support for powerpc.
>> 
>> https://lore.kernel.org/all/6e09dc28-4a2e-49d8-a2b5-ffb3396a9952@csgroup.eu/T/
>> 
>> Main change were:
>> 1. powerpc instruction nmemonic table to associate load/store
>> instructions with move_ops which is use to identify if instruction
>> is a memory access one.
>> 2. To get register number and access offset from the given
>> instruction, code uses fields from "struct arch" -> objump.
>> Added entry for powerpc here.
>> 3. A get_arch_regnum to return register number from the
>> register name string.
>> 
>> But the apporach used in the initial patchset used parsing of
>> disassembled code which the current perf tool implementation does.
>> 
>> Example: lwz     r10,0(r9)
>> 
>> This line "lwz r10,0(r9)" is parsed to extract instruction name,
>> registers names and offset. Also to find whether there is a memory
>> reference in the operands, "memory_ref_char" field of objdump is used.
>> For x86, "(" is used as memory_ref_char to tackle instructions of the
>> form "mov  (%rax), %rcx".
>> 
>> In case of powerpc, not all instructions using "(" are the only memory
>> instructions. Example, above instruction can also be of extended form (X
>> form) "lwzx r10,0,r19". Inorder to easy identify the instruction category
>> and extract the source/target registers, this patchset adds support to use
>> raw instruction. With raw instruction, macros are added to extract opcode
>> and register fields.
>> 
>> Example representation using --show-raw-insn in objdump gives result:
>> 
>> 38 01 81 e8     ld      r4,312(r1)
>> 
>> Here "38 01 81 e8" is the raw instruction representation. In powerpc,
>> this translates to instruction form: "ld RT,DS(RA)" and binary code
>> as:
>> _____________________________________
>> | 58 |  RT  |  RA |      DS       | |
>> -------------------------------------
>> 0    6     11    16              30 31
>> 
>> Patchset adds support to pick the opcode and reg fields from this
>> raw/binary instruction code. This approach came in from review comment
>> by Segher Boessenkool for the initial patchset.
>> 
>> Apart from that, instruction tracking is enabled for powerpc and
>> support function is added to find variables defined as registers
>> Example, in powerpc, two registers are
>> defined to represent variable:
>> 1. r13: represents local_paca
>> register struct paca_struct *local_paca asm("r13");
>> 
>> 2. r1: represents stack_pointer
>> register void *__stack_pointer asm("r1");
>> 
>> These are handled in this patchset.
>> 
>> - Patch 1 is to rearrange register state type structures to header file
>> so that it can referred from other arch specific files
>> - Patch 2 is to make instruction tracking as a callback to"struct arch"
>> so that it can be implemented by other archs easily and defined in arch
>> specific files
>> - Patch 3 is to fix a small comment
>> - Patch 4 adds support to capture and parse raw instruction in objdump
>> by keeping existing approach intact.
>> - Patch 5 update parameters for reg extract functions to use raw
>> instruction on powerpc
>> - Patch 6 and patch 7 handles instruction tracking for powerpc.
>> - Patch 8 and Patch 8 handles support to find global register variables
>> 
>> With the current patchset:
>> 
>> ./perf record -a -e mem-loads sleep 1
>> ./perf report -s type,typeoff --hierarchy --group --stdio
>> ./perf annotate --data-type --insn-stat
>> 
>> perf annotate logs:
>> 
>> Annotate Instruction stats
>> total 562, ok 441 (78.5%), bad 121 (21.5%)
>> 
>>  Name      :  Good   Bad
>> -----------------------------------------------------------
>>  ld        :   313    54
>>  lwz       :    51    32
>>  lbz       :    31     5
>>  ldx       :     6    21
>>  lhz       :    23     0
>>  lwa       :     4     3
>>  lwarx     :     5     0
>>  lwzx      :     2     2
>>  ldarx     :     3     0
>>  lwzu      :     2     0
>>  stdcx.    :     0     1
>>  nop       :     0     1
>>  ldu       :     1     0
>>  lbzx      :     0     1
>>  lwax      :     0     1
>> 
>> perf report logs:
>> 
>> # Samples: 1K of event 'mem-loads'
>> # Event count (approx.): 937238
>> #
>> # Overhead  Data Type  Data Type Offset
>> # ........  .........  ................
>> #
>>    48.81%  (unknown)  (unknown) +0 (no field)
>>    12.85%  long unsigned int  long unsigned int +0 (current_stack_pointer)
>>     4.68%  struct paca_struct  struct paca_struct +2312 (__current)
>>     4.57%  struct paca_struct  struct paca_struct +2354 (irq_soft_mask)
>>     2.68%  struct paca_struct  struct paca_struct +8 (paca_index)
>>     2.64%  struct paca_struct  struct paca_struct +2808 (canary)
>>     2.24%  struct paca_struct  struct paca_struct +48 (data_offset)
>>     1.41%  struct vm_fault  struct vm_fault +0 (vma)
>>     1.29%  struct task_struct  struct task_struct +276 (flags)
>>     1.03%  struct pt_regs  struct pt_regs +264 (user_regs.msr)
>>     1.00%  struct menu_device  struct menu_device +4 (tick_wakeup)
>>     0.90%  struct security_hook_list  struct security_hook_list +0 (list.next)
>>     0.76%  struct irq_desc  struct irq_desc +304 (irq_data.chip)
>>     0.76%  struct rq  struct rq +2856 (cpu)
> 
> Looks great!  I'm glad it worked on powerpc too.
> We still need to verify the returned type is properly annotated.
> But overall it looks really good, I will leave comments in reply.

Hi Namhyung

Thanks a lot for looking at the patchset and sharing the review comments.
I will address review comments and respond to them sooner.

Thanks
Athira
> 
> Thanks,
> Namhyung
> 
>> 
>> Thanks
>> Athira Rajeev
>> 
>> Changelog:
>> From v1->v2:
>> - Addressed suggestion from Christophe Leroy and Segher Boessenkool
>>  to use the binary code (raw insn) to fetch opcode, register and
>>  offset fields.
>> - Added support for instruction tracking in powerpc
>> - Find the register defined variables (r13 and r1 which points to
>>  local_paca and current_stack_pointer in powerpc)
>> 
>> Athira Rajeev (9):
>>  tools/perf: Move the data structures related to register  type to
>>    header file
>>  tools/perf: Add "update_insn_state" callback function to handle arch
>>    specific instruction tracking
>>  tools/perf: Fix a comment about multi_regs in extract_reg_offset
>>    function
>>  tools/perf: Add support to capture and parse raw instruction in
>>    objdump
>>  tools/perf: Update parameters for reg extract functions to use raw
>>    instruction on powerpc
>>  tools/perf: Update instruction tracking for powerpc
>>  tools/perf: Update instruction tracking with add instruction
>>  tools/perf: Add support to find global register variables using
>>    find_data_type_global_reg
>>  tools/perf: Add support for global_die to capture name of variable in
>>    case of register defined variable
>> 
>> tools/include/linux/string.h                  |   2 +
>> tools/lib/string.c                            |  13 +
>> .../perf/arch/powerpc/annotate/instructions.c |  84 +++
>> tools/perf/arch/powerpc/util/dwarf-regs.c     |  52 ++
>> tools/perf/arch/x86/annotate/instructions.c   | 383 +++++++++++++
>> tools/perf/util/annotate-data.c               | 519 +++---------------
>> tools/perf/util/annotate-data.h               |  78 +++
>> tools/perf/util/annotate.c                    |  32 +-
>> tools/perf/util/annotate.h                    |   1 +
>> tools/perf/util/disasm.c                      | 109 +++-
>> tools/perf/util/disasm.h                      |  17 +-
>> tools/perf/util/dwarf-aux.c                   |   1 +
>> tools/perf/util/dwarf-aux.h                   |   1 +
>> tools/perf/util/include/dwarf-regs.h          |  12 +
>> tools/perf/util/sort.c                        |   7 +-
>> 15 files changed, 854 insertions(+), 457 deletions(-)
>> 
>> --
>> 2.43.0




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