perf script: how to print user-space backtrace?

[Milian Wolff <mail@milianw.de>]

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Hey all,

I recorded a perf data file using

perf record --call-graph dwarf kwrite <some large file>

when I report it I see backtraces pointing to the user space code:

perf report --stdio -g graph --no-children
    16.36%  kwrite           libKF5TextEditor.so.5.13.0     [.] 
QArrayData::data                                                                                               
                     |
                     ---QArrayData::data
                        |          
                        |--15.46%-- QTypedArrayData<unsigned short>::data

but when I run perf script, I do not see _any_ backtraces into user space. 

perf script -F comm,tid,time,event,ip,sym,trace,period
:4898  4898 17486.943365:          1 cycles: 
                  25f83a native_write_msr_safe
                  234f8a __intel_pmu_enable_all
                  235010 intel_pmu_enable_all
                  22e1ec x86_pmu_enable
                  356fb7 perf_pmu_enable.part.53
                  35824d perf_event_context_sched_in.isra.64
                  358e0b perf_event_exec
                  3e8c93 setup_new_exec
                  439a9f load_elf_binary
                  3e7f48 search_binary_handler
                  3e89cf do_execveat_common.isra.15
                  3e8e4a sys_execve
                  78b895 return_from_execve

kwrite  4898 17486.943893:          1 cycles: 
kwrite  4898 17486.944211:          1 cycles: 
...
kwrite  4898 17486.953664:     461703 cycles: 
kwrite  4898 17486.953838:     490150 cycles: 
                  78d4c0 page_fault
kwrite  4898 17486.954009:     516694 cycles: 
...
kwrite  4898 17510.765568:     766937 cycles: 
                  78979b down_write
                  39bd82 unlink_file_vma
                  3944d0 free_pgtables
                  39eef6 exit_mmap
                  275d45 mmput
                  27b514 do_exit
                  27bdfb do_group_exit
                  27be84 [unknown]
                  78b56e system_call

So it looks to me as if only kernel-space call stacks are unwound in perf 
script. Is there a magic switch that I'm missing to get user-space stacks 
unwound? Note I'm using perf 4.1.0 on a Linux 4.1.2 system.

Thanks

-- 
Milian Wolff
mail@milianw.de
http://milianw.de

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