linux-kernel - Re: [PATCH v2 1/2] perf callchain: Create an address space per thread

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Date:	Tue, 30 Sep 2014 09:16:27 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Arun Sharma <asharma@...com>, David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jean Pihet <jean.pihet@...aro.org>
Subject: Re: [PATCH v2 1/2] perf callchain: Create an address space per thread

On Tue, Sep 30, 2014 at 03:11:21PM +0900, Namhyung Kim wrote:
> Hi Jiri,
> 
> On Mon, 29 Sep 2014 10:34:52 +0200, Jiri Olsa wrote:
> > On Mon, Sep 29, 2014 at 01:58:11PM +0900, Namhyung Kim wrote:
> >> @@ -37,6 +38,9 @@ struct thread *thread__new(pid_t pid, pid_t tid)
> >>  		thread->cpu = -1;
> >>  		INIT_LIST_HEAD(&thread->comm_list);
> >>  
> >> +		if (unwind__prepare_access(thread) < 0)
> >> +			goto err_thread;
> >
> > So this is something we need to do only for DWARF unwind via libunwind.
> > Do we want some condition to bypass this in for the rest of the cases?
> 
> Ah, you're right, we need to check that before doing this.
> 
> 
> >
> > I think we could check for symbol_conf.use_callchain and for the
> > PERF_SAMPLE_REGS_USER|PERF_SAMPLE_STACK_USER sample types in evlist,
> > something like:
> >
> >   bool has_dwarf_data_for_callchains = symbol_conf.use_callchain && evlist_sample_type_has(evlist, PERF_SAMPLE_REGS_USER|PERF_SAMPLE_STACK_USER)
> 
> Hmm.. it seems that it's hard to get the evlist at this point.  Maybe we
> need to add a field in the symbol_conf or a global variable.. :/

yea, symbol_conf seems ok

jirka
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