linux-kernel - Re: [PATCH] perf script: Initialize callchain_param.record

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Date:	Thu, 13 Aug 2015 10:53:36 +0200
From:	Milian Wolff <milian.wolff@...b.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Perf Users <linux-perf-users@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH] perf script: Initialize callchain_param.record_mode

On Thursday, August 13, 2015 09:17:24 AM Jiri Olsa wrote:
> On Wed, Jul 22, 2015 at 08:48:40PM +0200, Milian Wolff wrote:
> > 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.
> 
> hi,
> right you are.. does attached patch help?

<snip>

Hey Jiri,

it works a treat!

Many thanks, much appreciated.

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