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Date: Sat, 28 Mar 2015 10:03:28 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>, Arnaldo Carvalho de Melo <acme@kernel.org>,
        David Ahern <dsahern@gmail.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
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        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Tom Zanussi <tzanussi@gmail.com>, Wang Nan <wangnan0@huawei.com>,
        lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] perf build: Suppress warning about missing libbabeltrace
Message-ID: <20150328090328.GA5027@gmail.com>
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* Jiri Olsa <jolsa@redhat.com> wrote:

> On Fri, Mar 27, 2015 at 12:18:55PM +0100, Ingo Molnar wrote:
> > 
> > * Jiri Olsa <jolsa@kernel.org> wrote:
> > 
> > > Be silent about missing babeltrace library until the needed
> > > version (1.3) is pushed into most common distros.
> > > 
> > > Requested-by: Ingo Molnar <mingo@kernel.org>
> > > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > > Link: http://lkml.kernel.org/n/tip-95mcd8hoxyt43jighilggjej@git.kernel.org
> > > ---
> > >  tools/perf/config/Makefile | 7 ++++++-
> > >  1 file changed, 6 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
> > > index cd121dfc4de9..2d9142b10cd3 100644
> > > --- a/tools/perf/config/Makefile
> > > +++ b/tools/perf/config/Makefile
> > > @@ -606,7 +606,12 @@ ifndef NO_LIBBABELTRACE
> > >      EXTLIBS += -lbabeltrace-ctf
> > >      $(call detected,CONFIG_LIBBABELTRACE)
> > >    else
> > > -    msg := $(warning No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev);
> > > +#
> > > +# Be silent about missing babeltrace library
> > > +# until the needed version (1.3) is pushed
> > > +# into most common distros.
> > > +#
> > > +#    msg := $(warning No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev);
> > >      NO_LIBBABELTRACE := 1
> > >    endif
> > >  endif
> > 
> > But, but ... the feature detection is still executed, and it slows 
> > down the regular build on 99.9999% of the systems, right?
> > 
> 
> right, so currently all features are being checked by default and the
> only way to disable the check is via NO_* make variables
> 
> > I don't mind carrying the code, but could we make it such that it 
> > needs some special option to build or so?
> 
> I thought about this as of generic feature for all checks, but given
> that this is the only case so far, how about attached patch?
> 
> it's changing the NO_LIBBABELTRACE to LIBBABELTRACE so the libbabeltrace
> check is disabled unless you do:
> 
>   $ make LIBBABELTRACE=1
> 
> and we'd switch it back once the babeltrace 1.3 is in generic use

That sounds good to me!

Acked-by: Ingo Molnar <mingo@kernel.org>

Thanks,

	Ingo