linux-kernel - Re: [PATCH 1/8] perf tools: Omit DWARF judgement when recording dwarf callchain

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Date:	Mon, 9 May 2016 13:16:49 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	He Kuang <hekuang@...wei.com>, peterz@...radead.org,
	mingo@...hat.com, alexander.shishkin@...ux.intel.com,
	wangnan0@...wei.com, jpoimboe@...hat.com, ak@...ux.intel.com,
	eranian@...gle.com, namhyung@...nel.org, adrian.hunter@...el.com,
	sukadev@...ux.vnet.ibm.com, masami.hiramatsu.pt@...achi.com,
	tumanova@...ux.vnet.ibm.com, kan.liang@...el.com,
	penberg@...nel.org, dsahern@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] perf tools: Omit DWARF judgement when recording
 dwarf callchain

Em Sat, May 07, 2016 at 08:03:46PM +0200, Jiri Olsa escreveu:
> On Fri, May 06, 2016 at 08:59:07AM +0000, He Kuang wrote:
> > There's no need for dwarf support when perf recording with callchain.
> > 
> > Signed-off-by: He Kuang <hekuang@...wei.com>
> 
> Acked-by: Jiri Olsa <jolsa@...nel.org>

Ok, due to your Ack I went on to read the code and indeed, with this
changeset description:

"There is no need to check for DWARF unwinding support when using the
'dwarf' callchain record method, as this will only ask the kernel to
collect stack dumps for later DWARF CFI processing, which can be done
in another machine, where the support for DWARF unwinding need to be
present."

Thanks,

- Arnaldo
 
> thanks,
> jirka
> 
> > ---
> >  tools/perf/util/util.c | 2 --
> >  1 file changed, 2 deletions(-)
> > 
> > diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
> > index b7766c5..e5ebfd4 100644
> > --- a/tools/perf/util/util.c
> > +++ b/tools/perf/util/util.c
> > @@ -471,7 +471,6 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
> >  				       "needed for --call-graph fp\n");
> >  			break;
> >  
> > -#ifdef HAVE_DWARF_UNWIND_SUPPORT
> >  		/* Dwarf style */
> >  		} else if (!strncmp(name, "dwarf", sizeof("dwarf"))) {
> >  			const unsigned long default_stack_dump_size = 8192;
> > @@ -487,7 +486,6 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
> >  				ret = get_stack_size(tok, &size);
> >  				param->dump_size = size;
> >  			}
> > -#endif /* HAVE_DWARF_UNWIND_SUPPORT */
> >  		} else if (!strncmp(name, "lbr", sizeof("lbr"))) {
> >  			if (!strtok_r(NULL, ",", &saveptr)) {
> >  				param->record_mode = CALLCHAIN_LBR;
> > -- 
> > 1.8.5.2
> >