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Date: Tue, 10 Dec 2013 16:31:51 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
        linux-kernel@vger.kernel.org,
        Corey Ashford <cjashfor@linux.vnet.ibm.com>,
        Frederic Weisbecker <fweisbec@gmail.com>, Ingo Molnar <mingo@elte.hu>,
        Namhyung Kim <namhyung@kernel.org>, Paul Mackerras <paulus@samba.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Steven Rostedt <rostedt@goodmis.org>, David Ahern <dsahern@gmail.com>
Subject: Re: [PATCH 28/28] perf tools: Add udis86 disassembler feature check
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* Jiri Olsa <jolsa@redhat.com> wrote:

> On Thu, Dec 05, 2013 at 11:45:46AM +0100, Ingo Molnar wrote:
> 
> SNIP
> 
> > > > 
> > > > 1)
> > > > 
> > > > So, the first problem I can see is in the output:
> > > > 
> > > > Auto-detecting system features:
> > > > ...                     backtrace: [ on  ]
> > > > ...                         dwarf: [ on  ]
> > > > ...                fortify-source: [ on  ]
> > > > ...                         glibc: [ on  ]
> > > > ...                          gtk2: [ on  ]
> > > > ...                  gtk2-infobar: [ on  ]
> > > > ...                      libaudit: [ on  ]
> > > > ...                        libbfd: [ on  ]
> > > > ...                        libelf: [ on  ]
> > > > ...             libelf-getphdrnum: [ on  ]
> > > > ...                   libelf-mmap: [ on  ]
> > > > ...                       libnuma: [ on  ]
> > > > ...                       libperl: [ on  ]
> > > > ...                     libpython: [ on  ]
> > > > ...             libpython-version: [ on  ]
> > > > ...                      libslang: [ on  ]
> > > > ...                     libunwind: [ on  ]
> > > > ...                       on-exit: [ on  ]
> > > > ...            stackprotector-all: [ on  ]
> > > > ...                       timerfd: [ on  ]
> > > > 
> > > > config/Makefile:421: No udis86 support.
> > > > 
> > > > such a 'no XYZ support' message should only occur if a feature test 
> > > > failed. _If_ we decide that 'udis86' support is required for a full 
> > > > perf build then there should be a new line saying something like:
> > > > 
> > > > ...                        udis86: [ OFF ]
> > > 
> > > hum, just sent v4 that added udis86 into above list ;-)
> > > 
> > > So.. do we consider 'full perf build' to be build with all
> > > possible libraries linked in?
> > 
> > So my worry is, how widely is libudis86 available in distros? What is 
> > the package name on Debian/Ubuntu for example?
> 
> I did not find any.. :-\ I can see Fedora and Gentoo

That's a problem really - all perf developers who are using Ubuntu 
will see the failure, without being able to do anything about it.

So maybe we need an intermediate feature-mode for such convenience 
features that don't really impact measurement capabilities, those 
features could be probed but failures would not be displayed in such a 
highly prominent fashion.

Thanks,

	Ingo