Subject: Re: [PATCH V7 00/18] Add data type profiling support for powerpc

From: Namhyung Kim <[email-masked]>
Date: Wed, 17 Jul 2024 22:34:29 -0700

Hello,

On Sat, Jul 13, 2024 at 10:25:11PM +0530, Athira Rajeev 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/[email-masked]/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, second patchset added support to use
> raw instruction. With raw instruction, macros are added to extract opcode
> and register fields.
> Link to second patchset:
> https://lore.kernel.org/all/[email-masked]/
> 
> 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
> 
> Second patchset used "objdump" again to read the raw instruction.
> But since there is no need to disassemble and binary code can be read
> directly from the DSO, third patchset (ie this patchset) uses below
> apporach. The apporach preferred in powerpc to parse sample for data
> type profiling in V3 patchset is:
> - Read directly from DSO using dso__data_read_offset
> - If that fails for any case, fallback to using libcapstone
> - If libcapstone is not supported, approach will use objdump
> 
> 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 and Christophe 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, below 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 handle state type regs array size for x86 and powerpc
> - Patch 4 adds support to capture and parse raw instruction in powerpc
> using dso__data_read_offset utility
> - Patch 4 also adds logic to support using objdump when doing default "perf
> report" or "perf annotate" since it that needs disassembled instruction.
> - Patch 5 adds disasm_line__parse to parse raw instruction for powerpc
> - Patch 6 update parameters for reg extract functions to use raw
> instruction on powerpc
> - Patch 7 updates ins__find to carry raw_insn and also adds parse
> callback for memory instructions for powerpc
> - Patch 8 add support to identify memory instructions of opcode 31 in
> powerpc
> - Patch 9 adds more instructions to support instruction tracking in powerpc
> - Patch 10 and 11 handles instruction tracking for powerpc.
> - Patch 12, 13 and 14 add support to use libcapstone in powerpc
> - Patch 15 and patch 16 handles support to find global register variables
> - PAtch 17 updates data type compare functions data_type_cmp and
>   sort__typeoff_sort to include var_name along with type_name in
>   comparison.
> - Patch 18 handles insn-stat option for perf annotate
> 
> Note:
> - There are remaining unknowns (25%) as seen in annotate Instruction stats
> below.
> - This patchset is not tested on powerpc32. In next step of enhancements
> along with handling remaining unknowns, plan to cover powerpc32 changes
> based on how testing goes.
> 
> 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 609, ok 446 (73.2%), bad 163 (26.8%)
> 
>   Name/opcode         :  Good   Bad
>   -----------------------------------------------------------
>   58                  :   323    80
>   32                  :    49    43
>   34                  :    33    11
>   OP_31_XOP_LDX       :     8    20
>   40                  :    23     0
>   OP_31_XOP_LWARX     :     5     1
>   OP_31_XOP_LWZX      :     2     3
>   OP_31_XOP_LDARX     :     3     0
>   33                  :     0     2
>   OP_31_XOP_LBZX      :     0     1
>   OP_31_XOP_LWAX      :     0     1
>   OP_31_XOP_LHZX      :     0     1
>   
> perf report logs:
> =================
> 
>   Total Lost Samples: 0
> 
>   Samples: 1K of event 'mem-loads'
>   Event count (approx.): 937238
> 
>   Overhead  Data Type  Data Type Offset
>  ........  .........  ................
>     48.60%  (unknown)  (unknown) +0 (no field)
>     11.42%  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)
>      2.69%  struct paca_struct  struct paca_struct +2808 (canary)
>      2.68%  struct paca_struct  struct paca_struct +8 (paca_index)
>      2.24%  struct paca_struct  struct paca_struct +48 (data_offset)
>      1.43%  long unsigned int  long unsigned int +0 (no field)
>      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)
>      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)
>      0.72%  long long unsigned int  long long unsigned int +0 (no field)

Thanks for your work!  But I think you need to split the basic part and
global register support part which needs more review.

For the patch 1 to 14:
Reviewed-by: Namhyung Kim <[email-masked]>

Thanks,
Namhyung

> 
> Thanks
> Athira Rajeev
> 
> Changelog:
> From v6 -> v7:
> - Addressed review comments from Namhyung
>   Changed format string space to %-20s while printing
>   instruction stats in patch 18.
>   Use cmp_null in patch 17 while comparing var_name to
>   properly sort with correct order.
> 
> From v5 -> v6:
> - Addressed review comments from Namhyung
>   Conditionally define TYPE_STATE_MAX_REGS based on arch.
>   Added macro for defining width of the raw codes and spaces
>   in disasm_line__parse_powerpc.
>   Call disasm_line__parse from disasm_line__parse_powerpc
>   for generic code.
>   Renamed symbol__disassemble_dso to symbol__disassemble_raw.
>   Fixed find_data_type_global_reg to correclty free var_types
>   and change indent level.
>   Fixed data_type_cmp and sort__typeoff_sort to include var_name
>   in comparing data type entries.
>   
> From v4 -> v5:
> - Addressed review comments from Namhyung
>   Handle max number of type state regs as 16 for x86 and 32 for
>   powerpc.
>   Added generic support for objdump patch first and DSO read
>   optimisation next
>   combined patch 3 and patch 4 in patchseries V4 to one patch
>   Changed reference for "raw_insn" to use "u32"
>   Splitted "parse" callback patch changes and "ins__find" patch
>   changes into two
>   Instead of making weak function, added get_powerpc_regs to
>   extract register and offset fields for powerpc
> - Addressed complation fail when "dwarf.h" is not present ie
>   elfutils devel is not present. Used includes for #ifdef HAVE_DWARF_SUPPORT
>   when including functions that use Dwarf references. Also
>   conditionally include some of the header files.
> 
> From v3->v4:
> - Addressed review comments from Ian by using capston_init from
>   "util/print_insn.c" instead of "open_capston_handle".
> - Addressed review comment from Namhyung by moving "opcode"
>   field from "struct ins" to "struct disasm_line"
> 
> From v2->v3:
> - Addressed review comments from Christophe and Namhyung for V2
> - Changed the apporach in powerpc to parse sample for data
>   type profiling as:
>   Read directly from DSO using dso__data_read_offset
>   If that fails for any case, fallback to using libcapstone
>   If libcapstone is not supported, approach will use objdump
> - Include instructions with opcode as 31 and correctly categorize
>   them as memory or arithmetic instructions.
> - Include more instructions for instruction tracking in powerpc
> 
> 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 (18):
>   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: Update TYPE_STATE_MAX_REGS to include max of regs in
>     powerpc
>   tools/perf: Add disasm_line__parse to parse raw instruction for
>     powerpc
>   tools/perf: Add support to capture and parse raw instruction in
>     powerpc using dso__data_read_offset utility
>   tools/perf: Update parameters for reg extract functions to use raw
>     instruction on powerpc
>   tools/perf: Add parse function for memory instructions in powerpc
>   tools/perf: Add support to identify memory instructions of opcode 31
>     in powerpc
>   tools/perf: Add some of the arithmetic instructions to support
>     instruction tracking in powerpc
>   tools/perf: Add more instructions for instruction tracking
>   tools/perf: Update instruction tracking for powerpc
>   tools/perf: Make capstone_init non-static so that it can be used
>     during symbol disassemble
>   tools/perf: Use capstone_init and remove open_capstone_handle from
>     disasm.c
>   tools/perf: Add support to use libcapstone in powerpc
>   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/perf: Update data_type_cmp and sort__typeoff_sort function to
>     include var_name in comparison
>   tools/perf: Set instruction name to be used with insn-stat when using
>     raw instruction
> 
>  tools/include/linux/string.h                  |   2 +
>  tools/lib/string.c                            |  13 +
>  tools/perf/arch/arm64/annotate/instructions.c |   3 +-
>  .../arch/loongarch/annotate/instructions.c    |   6 +-
>  .../perf/arch/powerpc/annotate/instructions.c | 254 ++++++++
>  tools/perf/arch/powerpc/util/dwarf-regs.c     |  53 ++
>  tools/perf/arch/s390/annotate/instructions.c  |   5 +-
>  tools/perf/arch/x86/annotate/instructions.c   | 377 ++++++++++++
>  tools/perf/builtin-annotate.c                 |   4 +-
>  tools/perf/util/annotate-data.c               | 544 ++++--------------
>  tools/perf/util/annotate-data.h               |  83 +++
>  tools/perf/util/annotate.c                    |  29 +-
>  tools/perf/util/annotate.h                    |   6 +-
>  tools/perf/util/disasm.c                      | 468 +++++++++++++--
>  tools/perf/util/disasm.h                      |  19 +-
>  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/print_insn.c                  |  15 +-
>  tools/perf/util/print_insn.h                  |   5 +
>  tools/perf/util/sort.c                        |  25 +-
>  tools/perf/util/sort.h                        |   1 +
>  22 files changed, 1421 insertions(+), 505 deletions(-)
> 
> -- 
> 2.43.0
>