Re: [RFCv3 00/17] perf: Add backtrace post dwarf unwind

[Jiri Olsa]

hi,
any feedback?

thanks,
jirka

On Wed, May 02, 2012 at 01:37:01PM +0200, Jiri Olsa wrote:
> hi,
> sending another RFC version. This mainly includes more general
> version of perf regs and stack interface. Details are below
> and in patches' comments.. ;)
> 
> thanks for comments,
> jirka
> 
> v3 changes:
>    patch 01/17
>    - added HAVE_PERF_REGS config option
>    patch 02/17, 04/17
>    - regs and stack perf interface is more general now
>    patch 06/17
>    - unrelated online fix for i386 compilation
>    patch 16/17
>    - few namespace fixies
> 
> ---
> Adding the post unwinding user stack backtrace using dwarf unwind
> via libunwind. The original work was done by Frederic. I mostly took
> his patches and make them compile in current kernel code plus I added
> some stuff here and there.
> 
> The main idea is to store user registers and portion of user
> stack when the sample data during the record phase. Then during
> the report, when the data is presented, perform the actual dwarf
> dwarf unwind.
> 
> attached patches:
>  01/17 perf: Unified API to record selective sets of arch registers
>  02/17 perf: Add ability to attach registers dump to sample
>  03/17 perf: Factor __output_copy to be usable with specific copy function
>  04/17 perf: Add ability to attach user stack dump to sample
>  05/17 perf: Add attribute to filter out user callchains
>  06/17 perf, tool: Fix format string for x86-32 compilation
>  07/17 perf, tool: Factor DSO symtab types to generic binary types
>  08/17 perf, tool: Add interface to read DSO image data
>  09/17 perf, tool: Add '.note' check into search for NOTE section
>  10/17 perf, tool: Back [vdso] DSO with real data
>  11/17 perf, tool: Add interface to arch registers sets
>  12/17 perf, tool: Add libunwind dependency for dwarf cfi unwinding
>  13/17 perf, tool: Support user regs and stack in sample parsing
>  14/17 perf, tool: Support for dwarf cfi unwinding on post processing
>  15/17 perf, tool: Support for dwarf mode callchain on perf record
>  16/17 perf, tool: Add dso data caching
>  17/17 perf, tool: Add dso data caching tests
> 
> I tested on Fedora. There was not much gain on i386, because the
> binaries are compiled with frame pointers. Thought the dwarf
> backtrace is more accurade and unwraps calls in more details
> (functions that do not set the frame pointers).
> 
> I could see some improvement on x86_64, where I got full backtrace
> where current code could got just the first address out of the
> instruction pointer.
> 
> Example on x86_64:
> [dwarf]
>    perf record -g -e syscalls:sys_enter_write date
> 
>    100.00%     date  libc-2.14.90.so  [.] __GI___libc_write
>                |
>                --- __GI___libc_write
>                    _IO_file_write@@GLIBC_2.2.5
>                    new_do_write
>                    _IO_do_write@@GLIBC_2.2.5
>                    _IO_file_overflow@@GLIBC_2.2.5
>                    0x4022cd
>                    0x401ee6
>                    __libc_start_main
>                    0x4020b9
> 
> 
> [frame pointer]
>    perf record -g fp -e syscalls:sys_enter_write date
> 
>    100.00%     date  libc-2.14.90.so  [.] __GI___libc_write
>                |
>                --- __GI___libc_write
> 
> Also I tested on coreutils binaries mainly, but I could see
> getting wider backtraces with dwarf unwind for more complex
> application like firefox.
> 
> The unwind should go throught [vdso] object. I haven't studied
> the [vsyscall] yet, so not sure there.
> 
> Attached patches should work on both x86 and x86_64. I did
> some initial testing so far.
> 
> The unwind backtrace can be interrupted by following reasons:
>     - bug in unwind information of processed shared library
>     - bug in unwind processing code (most likely ;) )
>     - insufficient dump stack size
>     - wrong register value - x86_64 does not store whole
>       set of registers when in exception, but so far
>       it looks like RIP and RSP should be enough
> 
> thanks for comments,
> jirka
> ---
>  arch/Kconfig                                       |    6 +
>  arch/x86/Kconfig                                   |    1 +
>  arch/x86/include/asm/perf_event.h                  |    2 +
>  arch/x86/include/asm/perf_regs.h                   |   10 +
>  arch/x86/include/asm/perf_regs_32.h                |   84 +++
>  arch/x86/include/asm/perf_regs_64.h                |   99 ++++
>  include/linux/perf_event.h                         |   49 ++-
>  include/linux/perf_regs.h                          |   28 +
>  kernel/events/callchain.c                          |    4 +-
>  kernel/events/core.c                               |  204 +++++++-
>  kernel/events/internal.h                           |   65 ++-
>  kernel/events/ring_buffer.c                        |    4 +-
>  tools/perf/Makefile                                |   45 ++-
>  tools/perf/arch/x86/Makefile                       |    3 +
>  tools/perf/arch/x86/include/perf_regs.h            |  108 ++++
>  tools/perf/arch/x86/util/unwind.c                  |  111 ++++
>  tools/perf/builtin-record.c                        |   86 +++-
>  tools/perf/builtin-report.c                        |   26 +-
>  tools/perf/builtin-script.c                        |   56 ++-
>  tools/perf/builtin-test.c                          |    7 +-
>  tools/perf/builtin-top.c                           |    7 +-
>  tools/perf/config/feature-tests.mak                |   25 +
>  tools/perf/perf.h                                  |    9 +-
>  tools/perf/util/annotate.c                         |    2 +-
>  tools/perf/util/dso-test.c                         |  154 ++++++
>  tools/perf/util/event.h                            |   16 +-
>  tools/perf/util/evlist.c                           |   24 +
>  tools/perf/util/evlist.h                           |    3 +
>  tools/perf/util/evsel.c                            |   43 ++-
>  tools/perf/util/include/linux/compiler.h           |    1 +
>  tools/perf/util/map.c                              |   23 +-
>  tools/perf/util/map.h                              |    7 +-
>  tools/perf/util/perf_regs.h                        |   19 +
>  tools/perf/util/python.c                           |    3 +-
>  .../perf/util/scripting-engines/trace-event-perl.c |    3 +-
>  .../util/scripting-engines/trace-event-python.c    |    3 +-
>  tools/perf/util/session.c                          |  134 +++++-
>  tools/perf/util/session.h                          |   15 +-
>  tools/perf/util/symbol.c                           |  435 +++++++++++++---
>  tools/perf/util/symbol.h                           |   52 ++-
>  tools/perf/util/trace-event-scripting.c            |    3 +-
>  tools/perf/util/trace-event.h                      |    5 +-
>  tools/perf/util/unwind.c                           |  565 ++++++++++++++++++++
>  tools/perf/util/unwind.h                           |   34 ++
>  tools/perf/util/vdso.c                             |   90 +++
>  tools/perf/util/vdso.h                             |    8 +
>  46 files changed, 2488 insertions(+), 193 deletions(-)
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