Re: [PATCH v2] perf: libdw support for powerpc [ping]

Hi Paolo,

Thanks for the patch and really sorry for being late. I was quite busy
with few other things.

On Friday 09 June 2017 06:00 PM, Paolo Bonzini wrote:

On 01/06/2017 12:24, Paolo Bonzini wrote:

quoted

Porting PPC to libdw only needs an architecture-specific hook to move
the register state from perf to libdw.

The ARM and x86 architectures already use libdw, and it is useful to
have as much common code for the unwinder as possible.  Mark Wielaard
has contributed a frame-based unwinder to libdw, so that unwinding works
even for binaries that do not have CFI information.  In addition,
libunwind is always preferred to libdw by the build machinery so this
cannot introduce regressions on machines that have both libunwind and
libdw installed.

Cc: acme@kernel.org
Cc: Naveen N. Rao <redacted>
Cc: Ravi Bangoria <redacted>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
	v1->v2: fix for 4.11->4.12 changes

Ravi, Naveen, any reviews?

So, I tested this patch along with Mark's patch[1] on elfutils an looks
like it's not working. Steps on what I did:

After applying Mark's patch on upstream elfutils:

  $ aclocal
  $ autoheader
  $ autoconf
  $ automake --add-missing
  $ ./configure
  $ make
  $ make install DESTDIR=/home/ravi/elfutils-git

After applying your patch on upstream perf:

  $ make
  $ ./perf record --call-graph=dwarf ls
  $ LD_LIBRARY_PATH=/home/ravi/elfutils-git/usr/local/lib:\
    /home/ravi/elfutils-git/usr/local/lib/elfutils/:$LD_LIBRARY_PATH \
    ./perf script

    ls 44159  1800.878468:     191408 cycles:u:

    ls 44159  1800.878673:     419356 cycles:u:
                       8a97c hpte_need_flush (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                       835f4 flush_hash_page (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                       8acec hpte_need_flush (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                      3468f4 ptep_clear_flush (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                      328b10 wp_page_copy (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                      32ebe4 do_wp_page (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                      33434c __handle_mm_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                      335040 handle_mm_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                       7bf94 do_page_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                       1a4f8 handle_page_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)

    ls 44159  1800.878961:     430876 cycles:u:

    ls 44159  1800.879195:     423785 cycles:u:

    ls 44159  1800.879360:     427359 cycles:u:

Here I don't see userspace callchain getting unwound. Please let me know
if I'm doing anything wrong. Same perf.data with libunwind:

    ls 44159  1800.878468:     191408 cycles:u:
                       20380 _dl_sysdep_start (/usr/lib64/ld-2.17.so)
                        1c7f _dl_start_final (/usr/lib64/ld-2.17.so)
                        5ce7 _dl_start (/usr/lib64/ld-2.17.so)
                        1937 _start (/usr/lib64/ld-2.17.so)

    ls 44159  1800.878673:     419356 cycles:u:
                       8a97c hpte_need_flush (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                       835f4 flush_hash_page (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                       8acec hpte_need_flush (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                      3468f4 ptep_clear_flush (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                      328b10 wp_page_copy (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                      32ebe4 do_wp_page (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                      33434c __handle_mm_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                      335040 handle_mm_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                       7bf94 do_page_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                       1a4f8 handle_page_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                        7cd4 _dl_map_object_from_fd (/usr/lib64/ld-2.17.so)
                        b24b _dl_map_object (/usr/lib64/ld-2.17.so)
                       12b3b openaux (/usr/lib64/ld-2.17.so)
                       159bf _dl_catch_error (/usr/lib64/ld-2.17.so)
                       13323 _dl_map_object_deps (/usr/lib64/ld-2.17.so)
                        3feb dl_main (/usr/lib64/ld-2.17.so)
                       2045b _dl_sysdep_start (/usr/lib64/ld-2.17.so)
                        1c7f _dl_start_final (/usr/lib64/ld-2.17.so)
                        5ce7 _dl_start (/usr/lib64/ld-2.17.so)
                        1937 _start (/usr/lib64/ld-2.17.so)

    ls 44159  1800.878961:     430876 cycles:u:
                        dcb8 check_match.10245 (/usr/lib64/ld-2.17.so)
                        e55b do_lookup_x (/usr/lib64/ld-2.17.so)
                        e8d7 _dl_lookup_symbol_x (/usr/lib64/ld-2.17.so)
                       10493 _dl_relocate_object (/usr/lib64/ld-2.17.so)
                        4cf7 dl_main (/usr/lib64/ld-2.17.so)
                       2045b _dl_sysdep_start (/usr/lib64/ld-2.17.so)
                        1c7f _dl_start_final (/usr/lib64/ld-2.17.so)
                        5ce7 _dl_start (/usr/lib64/ld-2.17.so)
                        1937 _start (/usr/lib64/ld-2.17.so)

    ls 44159  1800.879195:     423785 cycles:u:
                       960a0 malloc (/usr/lib64/libc-2.17.so)
                       32a53 _nl_intern_locale_data (/usr/lib64/libc-2.17.so)
                       3337f _nl_load_locale_from_archive (/usr/lib64/libc-2.17.so)
                       323b3 _nl_find_locale (/usr/lib64/libc-2.17.so)
                       31b93 setlocale (/usr/lib64/libc-2.17.so)
                        2a8b _init (/usr/bin/ls)
                       2497f generic_start_main.isra.0 (/usr/lib64/libc-2.17.so)
                       24b73 __libc_start_main (/usr/lib64/libc-2.17.so)

    ls 44159  1800.879360:     427359 cycles:u:
                       a42b8 get_next_seq (/usr/lib64/libc-2.17.so)
                       a54ff __strcoll_l (/usr/lib64/libc-2.17.so)


[1] https://sourceware.org/ml/elfutils-devel/2017-q2/msg00223.html