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

Started byPaolo Bonzini <pbonzini@redhat.com>
First post2017-06-09 14:40 +0200
Last post2017-06-16 06:30 +0200
Articles 7 — 4 participants

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  Re: [PATCH v2] perf: libdw support for powerpc [ping] Paolo Bonzini <pbonzini@redhat.com> - 2017-06-09 14:40 +0200
    Re: [PATCH v2] perf: libdw support for powerpc [ping] Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> - 2017-06-12 14:00 +0200
      Re: [PATCH v2] perf: libdw support for powerpc [ping] Mark Wielaard <mark@klomp.org> - 2017-06-13 14:00 +0200
        Re: [PATCH v2] perf: libdw support for powerpc [ping] Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> - 2017-06-13 18:00 +0200
          Re: [PATCH v2] perf: libdw support for powerpc [ping] Milian Wolff <milian.wolff@kdab.com> - 2017-06-15 10:50 +0200
            Re: [PATCH v2] perf: libdw support for powerpc [ping] Mark Wielaard <mark@klomp.org> - 2017-06-15 13:20 +0200
              Re: [PATCH v2] perf: libdw support for powerpc [ping] Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> - 2017-06-16 06:30 +0200

#1662379 — Re: [PATCH v2] perf: libdw support for powerpc [ping]

FromPaolo Bonzini <pbonzini@redhat.com>
Date2017-06-09 14:40 +0200
SubjectRe: [PATCH v2] perf: libdw support for powerpc [ping]
Message-ID<tQrmN-1vk-3@gated-at.bofh.it>

On 01/06/2017 12:24, Paolo Bonzini wrote:
> 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 <naveen.n.rao@linux.vnet.ibm.com>
> Cc: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
> 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?

Thanks,

Paolo

> 
>  tools/perf/Makefile.config                  |  2 +-
>  tools/perf/arch/powerpc/util/Build          |  2 +
>  tools/perf/arch/powerpc/util/unwind-libdw.c | 73 +++++++++++++++++++++++++++++
>  3 files changed, 76 insertions(+), 1 deletion(-)
>  create mode 100644 tools/perf/arch/powerpc/util/unwind-libdw.c
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 8354d04b392f..e7b04a729417 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -61,7 +61,7 @@ endif
>  # Disable it on all other architectures in case libdw unwind
>  # support is detected in system. Add supported architectures
>  # to the check.
> -ifneq ($(ARCH),$(filter $(ARCH),x86 arm))
> +ifneq ($(ARCH),$(filter $(ARCH),x86 arm powerpc))
>    NO_LIBDW_DWARF_UNWIND := 1
>  endif
>  
> diff --git a/tools/perf/arch/powerpc/util/Build b/tools/perf/arch/powerpc/util/Build
> index 90ad64b231cd..2e6595310420 100644
> --- a/tools/perf/arch/powerpc/util/Build
> +++ b/tools/perf/arch/powerpc/util/Build
> @@ -5,4 +5,6 @@ libperf-y += perf_regs.o
>  
>  libperf-$(CONFIG_DWARF) += dwarf-regs.o
>  libperf-$(CONFIG_DWARF) += skip-callchain-idx.o
> +
>  libperf-$(CONFIG_LIBUNWIND) += unwind-libunwind.o
> +libperf-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> diff --git a/tools/perf/arch/powerpc/util/unwind-libdw.c b/tools/perf/arch/powerpc/util/unwind-libdw.c
> new file mode 100644
> index 000000000000..3a24b3c43273
> --- /dev/null
> +++ b/tools/perf/arch/powerpc/util/unwind-libdw.c
> @@ -0,0 +1,73 @@
> +#include <elfutils/libdwfl.h>
> +#include "../../util/unwind-libdw.h"
> +#include "../../util/perf_regs.h"
> +#include "../../util/event.h"
> +
> +/* See backends/ppc_initreg.c and backends/ppc_regs.c in elfutils.  */
> +static const int special_regs[3][2] = {
> +	{ 65, PERF_REG_POWERPC_LINK },
> +	{ 101, PERF_REG_POWERPC_XER },
> +	{ 109, PERF_REG_POWERPC_CTR },
> +};
> +
> +bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> +{
> +	struct unwind_info *ui = arg;
> +	struct regs_dump *user_regs = &ui->sample->user_regs;
> +	Dwarf_Word dwarf_regs[32], dwarf_nip;
> +	size_t i;
> +
> +#define REG(r) ({						\
> +	Dwarf_Word val = 0;					\
> +	perf_reg_value(&val, user_regs, PERF_REG_POWERPC_##r);	\
> +	val;							\
> +})
> +
> +	dwarf_regs[0]  = REG(R0);
> +	dwarf_regs[1]  = REG(R1);
> +	dwarf_regs[2]  = REG(R2);
> +	dwarf_regs[3]  = REG(R3);
> +	dwarf_regs[4]  = REG(R4);
> +	dwarf_regs[5]  = REG(R5);
> +	dwarf_regs[6]  = REG(R6);
> +	dwarf_regs[7]  = REG(R7);
> +	dwarf_regs[8]  = REG(R8);
> +	dwarf_regs[9]  = REG(R9);
> +	dwarf_regs[10] = REG(R10);
> +	dwarf_regs[11] = REG(R11);
> +	dwarf_regs[12] = REG(R12);
> +	dwarf_regs[13] = REG(R13);
> +	dwarf_regs[14] = REG(R14);
> +	dwarf_regs[15] = REG(R15);
> +	dwarf_regs[16] = REG(R16);
> +	dwarf_regs[17] = REG(R17);
> +	dwarf_regs[18] = REG(R18);
> +	dwarf_regs[19] = REG(R19);
> +	dwarf_regs[20] = REG(R20);
> +	dwarf_regs[21] = REG(R21);
> +	dwarf_regs[22] = REG(R22);
> +	dwarf_regs[23] = REG(R23);
> +	dwarf_regs[24] = REG(R24);
> +	dwarf_regs[25] = REG(R25);
> +	dwarf_regs[26] = REG(R26);
> +	dwarf_regs[27] = REG(R27);
> +	dwarf_regs[28] = REG(R28);
> +	dwarf_regs[29] = REG(R29);
> +	dwarf_regs[30] = REG(R30);
> +	dwarf_regs[31] = REG(R31);
> +	if (!dwfl_thread_state_registers(thread, 0, 32, dwarf_regs))
> +		return false;
> +
> +	dwarf_nip = REG(NIP);
> +	dwfl_thread_state_register_pc(thread, dwarf_nip);
> +	for (i = 0; i < ARRAY_SIZE(special_regs); i++) {
> +		Dwarf_Word val = 0;
> +		perf_reg_value(&val, user_regs, special_regs[i][1]);
> +		if (!dwfl_thread_state_registers(thread,
> +						 special_regs[i][0], 1,
> +						 &val))
> +			return false;
> +	}
> +
> +	return true;
> +}
>

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#1663444

FromRavi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Date2017-06-12 14:00 +0200
Message-ID<tRwaJ-1Dv-3@gated-at.bofh.it>
In reply to#1662379
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:
>> 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 <naveen.n.rao@linux.vnet.ibm.com>
>> Cc: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
>> 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

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#1664773

FromMark Wielaard <mark@klomp.org>
Date2017-06-13 14:00 +0200
Message-ID<tRSEh-7vV-1@gated-at.bofh.it>
In reply to#1663444
Hi Ravi,

On Mon, 2017-06-12 at 17:28 +0530, Ravi Bangoria wrote:
> 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.

I see the same on very short runs. But when doing a slightly longer run,
even just using ls -lahR, which does some more work, then I do see user
backtraces. They are still missing for some of the early samples though.
It is as if there is a stack/memory address mismatch when the probe is
"too early" in ld.so.

Could you do a test run on some program that does some more work to see
if you never get any user stack traces, or if you only not get them for
some specific probes?

Thanks,

Mark

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#1664974

FromRavi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Date2017-06-13 18:00 +0200
Message-ID<tRWox-1oA-1@gated-at.bofh.it>
In reply to#1664773
Hi Mark,

On Tuesday 13 June 2017 05:14 PM, Mark Wielaard wrote:
> I see the same on very short runs. But when doing a slightly longer run,
> even just using ls -lahR, which does some more work, then I do see user
> backtraces. They are still missing for some of the early samples though.
> It is as if there is a stack/memory address mismatch when the probe is
> "too early" in ld.so.
>
> Could you do a test run on some program that does some more work to see
> if you never get any user stack traces, or if you only not get them for
> some specific probes?

Thanks for checking. I tried a proper workload this time, but I still
don't see any userspace callchain getting unwound.

  $ ./perf record --call-graph=dwarf -- zip -q -r temp.zip .
  [ perf record: Woken up 2891 times to write data ]
  [ perf record: Captured and wrote 723.290 MB perf.data (87934 samples) ]


With libdw:

 $ LD_LIBRARY_PATH=/home/ravi/elfutils-git/usr/local/lib:\
    /home/ravi/elfutils-git/usr/local/lib/elfutils/:$LD_LIBRARY_PATH\
    ./perf script

  zip 16699  6857.354633:      37371 cycles:u:
                   ecedc xmon_core (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                   8c4fc __hash_page_64K (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                   83450 hash_preload (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                   7cc34 update_mmu_cache (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                  330064 alloc_set_pte (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                  330efc do_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                  334580 __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)
                   7bec4 do_page_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                   7be78 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)

  zip 16699  6857.354663:     300677 cycles:u:

  zip 16699  6857.354895:     584131 cycles:u:

  zip 16699  6857.355312:     589687 cycles:u:

  zip 16699  6857.355606:     560142 cycles:u:


With libunwind:

$ ./perf script

  zip 16699  6857.354633:      37371 cycles:u:
                     ecedc xmon_core (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                     8c4fc __hash_page_64K (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                     83450 hash_preload (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                     7cc34 update_mmu_cache (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                    330064 alloc_set_pte (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                    330efc do_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                    334580 __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)
                     7bec4 do_page_fault (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
                     7be78 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)
                      1920 _start (/usr/lib64/ld-2.17.so)

  zip 16699  6857.354663:     300677 cycles:u:
                      fa38 _dl_new_object (/usr/lib64/ld-2.17.so)
                      3073 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)

  zip 16699  6857.354895:     584131 cycles:u:
                     103d0 _dl_relocate_object (/usr/lib64/ld-2.17.so)

  zip 16699  6857.355312:     589687 cycles:u:
                      df68 do_lookup_x (/usr/lib64/ld-2.17.so)
                      e8d7 _dl_lookup_symbol_x (/usr/lib64/ld-2.17.so)
                     14bb3 _dl_fixup (/usr/lib64/ld-2.17.so)
                     1ef37 _dl_runtime_resolve (/usr/lib64/ld-2.17.so)
                     20bf7 copy_args (/usr/bin/zip)
                      286f main (/usr/bin/zip)
                     2497f generic_start_main.isra.0 (/usr/lib64/libc-2.17.so)
                     24b73 __libc_start_main (/usr/lib64/libc-2.17.so)

  zip 16699  6857.355606:     560142 cycles:u:
                     84764 _IO_getc (/usr/lib64/libc-2.17.so)
                      c4d7 find_next_signature (/usr/bin/zip)
                     15c8b readzipfile (/usr/bin/zip)
                      3477 main (/usr/bin/zip)
                     2497f generic_start_main.isra.0 (/usr/lib64/libc-2.17.so)
                     24b73 __libc_start_main (/usr/lib64/libc-2.17.so)


Right now, I'm busy with few other things so I'm not able to dig further.
But I can look into this next week or so.

Thanks,
Ravi

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#1666569

FromMilian Wolff <milian.wolff@kdab.com>
Date2017-06-15 10:50 +0200
Message-ID<tSyDw-cv-23@gated-at.bofh.it>
In reply to#1664974

[Multipart message — attachments visible in raw view] — view raw

On Tuesday, June 13, 2017 5:55:09 PM CEST Ravi Bangoria wrote:
> Hi Mark,
> 
> On Tuesday 13 June 2017 05:14 PM, Mark Wielaard wrote:
> > I see the same on very short runs. But when doing a slightly longer run,
> > even just using ls -lahR, which does some more work, then I do see user
> > backtraces. They are still missing for some of the early samples though.
> > It is as if there is a stack/memory address mismatch when the probe is
> > "too early" in ld.so.
> > 
> > Could you do a test run on some program that does some more work to see
> > if you never get any user stack traces, or if you only not get them for
> > some specific probes?
> 
> Thanks for checking. I tried a proper workload this time, but I still
> don't see any userspace callchain getting unwound.
> 
>   $ ./perf record --call-graph=dwarf -- zip -q -r temp.zip .
>   [ perf record: Woken up 2891 times to write data ]
>   [ perf record: Captured and wrote 723.290 MB perf.data (87934 samples) ]
> 
> 
> With libdw:
> 
>  $ LD_LIBRARY_PATH=/home/ravi/elfutils-git/usr/local/lib:\
>     /home/ravi/elfutils-git/usr/local/lib/elfutils/:$LD_LIBRARY_PATH\
>     ./perf script
> 
>   zip 16699  6857.354633:      37371 cycles:u:
>                    ecedc xmon_core
> (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux) 8c4fc
> __hash_page_64K (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
> 83450 hash_preload
> (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux) 7cc34
> update_mmu_cache (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux)
> 330064 alloc_set_pte
> (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux) 330efc do_fault
> (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux) 334580
> __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)
> 7bec4 do_page_fault
> (/usr/lib/debug/lib/modules/4.11.0-3.el7.ppc64le/vmlinux) 7be78
> 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)
> 
>   zip 16699  6857.354663:     300677 cycles:u:
> 
>   zip 16699  6857.354895:     584131 cycles:u:
> 
>   zip 16699  6857.355312:     589687 cycles:u:
> 
>   zip 16699  6857.355606:     560142 cycles:u:

Just a quick question: Have you guys applied my recent patch:

commit 5ea0416f51cc93436bbe497c62ab49fd9cb245b6
Author: Milian Wolff <milian.wolff@kdab.com>
Date:   Thu Jun 1 23:00:21 2017 +0200

    perf report: Include partial stacks unwound with libdw
    
    So far the whole stack was thrown away when any error occurred before
    the maximum stack depth was unwound. This is actually a very common
    scenario though. The stacks that got unwound so far are still
    interesting. This removes a large chunk of differences when comparing
    perf script output for libunwind and libdw perf unwinding.

If not, then this could explain the issue you are seeing.

Cheers

-- 
Milian Wolff | milian.wolff@kdab.com | Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts

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#1666668

FromMark Wielaard <mark@klomp.org>
Date2017-06-15 13:20 +0200
Message-ID<tSAYG-1Mg-23@gated-at.bofh.it>
In reply to#1666569
On Thu, 2017-06-15 at 10:46 +0200, Milian Wolff wrote:
> Just a quick question: Have you guys applied my recent patch:
> 
> commit 5ea0416f51cc93436bbe497c62ab49fd9cb245b6
> Author: Milian Wolff <milian.wolff@kdab.com>
> Date:   Thu Jun 1 23:00:21 2017 +0200
> 
>     perf report: Include partial stacks unwound with libdw
>     
>     So far the whole stack was thrown away when any error occurred before
>     the maximum stack depth was unwound. This is actually a very common
>     scenario though. The stacks that got unwound so far are still
>     interesting. This removes a large chunk of differences when comparing
>     perf script output for libunwind and libdw perf unwinding.
> 
> If not, then this could explain the issue you are seeing.

Thanks! No, I didn't have that patch (*) yet. It makes a huge
difference. With that, Paolo's patch and the elfutils libdw powerpc64
fallback unwinder patch, it looks like I get user stack traces for
everything now on ppc64le.

Cheers,

Mark

(*) It just this one-liner, but what a difference that makes:

--- a/tools/perf/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw.c
@@ -224,7 +224,7 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 
        err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);
 
-       if (err && !ui->max_stack)
+       if (err && ui->max_stack != max_stack)
                err = 0;
 
        /*

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#1667406

FromRavi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Date2017-06-16 06:30 +0200
Message-ID<tSR3s-3AU-5@gated-at.bofh.it>
In reply to#1666668
Works like a charm with Milian's patch.

Acked-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>

Note:
I still see very minor differences between libunwind and libdw. Also, second last
function gets repeated two times in every callchain but it can be fixed later on.
Otherwise all looks good!

Thanks,
-Ravi

On Thursday 15 June 2017 04:46 PM, Mark Wielaard wrote:
> On Thu, 2017-06-15 at 10:46 +0200, Milian Wolff wrote:
>> Just a quick question: Have you guys applied my recent patch:
>>
>> commit 5ea0416f51cc93436bbe497c62ab49fd9cb245b6
>> Author: Milian Wolff <milian.wolff@kdab.com>
>> Date:   Thu Jun 1 23:00:21 2017 +0200
>>
>>     perf report: Include partial stacks unwound with libdw
>>     
>>     So far the whole stack was thrown away when any error occurred before
>>     the maximum stack depth was unwound. This is actually a very common
>>     scenario though. The stacks that got unwound so far are still
>>     interesting. This removes a large chunk of differences when comparing
>>     perf script output for libunwind and libdw perf unwinding.
>>
>> If not, then this could explain the issue you are seeing.
> Thanks! No, I didn't have that patch (*) yet. It makes a huge
> difference. With that, Paolo's patch and the elfutils libdw powerpc64
> fallback unwinder patch, it looks like I get user stack traces for
> everything now on ppc64le.
>
> Cheers,
>
> Mark
>
> (*) It just this one-liner, but what a difference that makes:
>
> --- a/tools/perf/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw.c
> @@ -224,7 +224,7 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
>  
>         err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);
>  
> -       if (err && !ui->max_stack)
> +       if (err && ui->max_stack != max_stack)
>                 err = 0;
>  
>         /*
>

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