linux-kernel - Re: [PATCH] perf build: Suppress warning about missing libbabeltrace

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Date:	Fri, 27 Mar 2015 14:30:15 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Jiri Olsa <jolsa@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jeremie Galarneau <jgalar@...icios.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Tom Zanussi <tzanussi@...il.com>,
	Wang Nan <wangnan0@...wei.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf build: Suppress warning about missing libbabeltrace

On Fri, Mar 27, 2015 at 12:18:55PM +0100, Ingo Molnar wrote:
> 
> * Jiri Olsa <jolsa@...nel.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@...nel.org>
> > Signed-off-by: Jiri Olsa <jolsa@...nel.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

jirka


---
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index e9925e6ad1d0..c43a20517591 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -69,7 +69,7 @@ include config/utilities.mak
 #
 # Define NO_ZLIB if you do not want to support compressed kernel modules
 #
-# Define NO_LIBBABELTRACE if you do not want libbabeltrace support
+# Define LIBBABELTRACE if you DO want libbabeltrace support
 # for CTF data format.
 #
 # Define NO_LZMA if you do not want to support compressed (xz) kernel modules
diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
index cd121dfc4de9..59a98c643240 100644
--- a/tools/perf/config/Makefile
+++ b/tools/perf/config/Makefile
@@ -95,7 +95,7 @@ ifndef NO_LIBELF
   FEATURE_CHECK_LDFLAGS-libdw-dwarf-unwind := $(LIBDW_LDFLAGS) -ldw
 endif
 
-ifndef NO_LIBBABELTRACE
+ifdef LIBBABELTRACE
   # for linking with debug library, run like:
   # make DEBUG=1 LIBBABELTRACE_DIR=/opt/libbabeltrace/
   ifdef LIBBABELTRACE_DIR
@@ -598,7 +598,7 @@ else
   NO_PERF_READ_VDSOX32 := 1
 endif
 
-ifndef NO_LIBBABELTRACE
+ifdef LIBBABELTRACE
   $(call feature_check,libbabeltrace)
   ifeq ($(feature-libbabeltrace), 1)
     CFLAGS += -DHAVE_LIBBABELTRACE_SUPPORT $(LIBBABELTRACE_CFLAGS)
@@ -607,7 +607,6 @@ ifndef NO_LIBBABELTRACE
     $(call detected,CONFIG_LIBBABELTRACE)
   else
     msg := $(warning No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev);
-    NO_LIBBABELTRACE := 1
   endif
 endif
 
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