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Date: Tue, 18 Mar 2014 14:31:31 +0100
From: Jiri Olsa <jolsa@redhat.com>
To: Namhyung Kim <namhyung@kernel.org>
Cc: linux-kernel@vger.kernel.org, Don Zickus <dzickus@redhat.com>,
        Corey Ashford <cjashfor@linux.vnet.ibm.com>,
        David Ahern <dsahern@gmail.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Ingo Molnar <mingo@kernel.org>, Paul Mackerras <paulus@samba.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Subject: Re: [PATCH 3/5] perf tools: Allocate thread map_groups dynamicaly
Message-ID: <20140318133131.GB7845@krava.brq.redhat.com>
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On Tue, Mar 18, 2014 at 04:03:41PM +0900, Namhyung Kim wrote:
> Hi Jiri,
> 
> On Mon, 17 Mar 2014 15:52:59 +0100, Jiri Olsa wrote:
> > On Mon, Mar 17, 2014 at 04:13:53PM +0900, Namhyung Kim wrote:
> >> On Fri, 14 Mar 2014 15:00:04 +0100, Jiri Olsa wrote:
> >> > Moving towards sharing map groups within a process threads.
> >> >
> >> > Because of this we need the map groups to be dynamically
> >> > allocated. No other functional change is intended in here.
> >> > @@ -664,7 +664,7 @@ void thread__find_addr_map(struct thread *thread,
> >> >  	al->cpumode = cpumode;
> >> >  	al->filtered = false;
> >> >  
> >> > -	if (machine == NULL) {
> >> > +	if ((machine == NULL) || (mg == NULL)) {
> >> >  		al->map = NULL;
> >> >  		return;
> >> >  	}
> >> 
> >> What about the kernel threads?  I guess they're not using thread->mg but
> >> machine->kmaps instead?
> >
> > The machine->kmaps is used to store kernel maps - core + modules.
> >
> > All threads (including kernel ones) are using thread->mg,
> > kernel threads have empty /proc/x/maps file.
> >
> > In case the sample address is detected within kernel space,
> > the machine->kmaps is used instead of thread->mg:
> 
> That means kernel threads don't need to allocate ->mg, right?  So I'd
> suggest checking cpumode first and then allocate ->mg for userspace maps
> only.

good idea, will do

thanks,
jirka