linux-kernel - Re: [GIT PULL 00/12] perf/core improvements and fixes

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Message-ID: <20140227124047.GF9614@krava.brq.redhat.com>
Date:	Thu, 27 Feb 2014 13:40:47 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...radead.org>,
	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Cody P Schafer <cody@...ux.vnet.ibm.com>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jean Pihet <jean.pihet@...aro.org>,
	Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [GIT PULL 00/12] perf/core improvements and fixes

On Thu, Feb 27, 2014 at 01:30:52PM +0100, Ingo Molnar wrote:
> 
> * Jiri Olsa <jolsa@...hat.com> wrote:
> 
> > On Thu, Feb 27, 2014 at 12:46:58PM +0100, Ingo Molnar wrote:
> > > 
> > > * Arnaldo Carvalho de Melo <acme@...radead.org> wrote:
> > > 
> > > > From: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
> > > > 

SNIP

> > > Pulled, thanks a lot Arnaldo!
> > > 
> > > Btw., the build output looks weird now - on a system that used to pass 
> > > all feature tests there's this output:
> > > 
> > >   BUILD:   Doing 'make -j12' parallel build
> > > config/Makefile:288: No libdw DWARF unwind found, Please install 
> > > elfutils-devel/libdw-dev >= 0.158 and/or set LIBDW_DIR
> > > 
> > > Auto-detecting system features:
> > > ...                         dwarf: [ on  ]
> > > ...                         glibc: [ on  ]
> > > ...                          gtk2: [ on  ]
> > > ...                      libaudit: [ on  ]
> > > ...                        libbfd: [ on  ]
> > > ...                        libelf: [ on  ]
> > > ...                       libnuma: [ on  ]
> > > ...                       libperl: [ on  ]
> > > ...                     libpython: [ on  ]
> > > ...                      libslang: [ on  ]
> > > ...                     libunwind: [ on  ]
> > > ...            libdw-dwarf-unwind: [ OFF ]
> > > ...     DWARF post unwind library: libunwind
> > > 
> > > but:
> > > 
> > >    Package elfutils-devel-0.156-5.fc19.x86_64 already installed and latest version
> > > 
> > > Also, the information content of this line is unclear to me:
> > > 
> > > ...     DWARF post unwind library: libunwind
> > > 
> > > 
> > > what does that line want to tell?
> > 
> > this tells what DWARF unwind library is compiled
> > in.. 'libunwind' in this case
> 
> So my (stylistic) complaint is that it's really reading weird in a 
> table generated with the following purpose:
> 
>       Auto-detecting system features:
> 
> Also, we already know that libunwind is present, because just in the 
> line before it, it says:
> 
>     ...                     libunwind: [ on  ]
> 
> So it's doubly confusing. How about not displaying that line at all? 
> Is there a strong reason to not keep 'OFF' messages on a single line?

well, on/OFF lines are only about detecting libs

this line:
'DWARF post unwind library: libunwind'

is about telling which one goes in.. could be you have both
libraries detected and need to choose one or keep default

> 
> > the other choice is 'libdw', which was not detected in your case 
> > (and thats what the 1st message tells you)
> > 
> > we discussed with Arnaldo, that we would not display warnings for 
> > missing features by default.. only tell that there are missing 
> > features and display them for verbose (VF=1) output
> 
> That's probably a good plan. I'd suggest the following 'short log' for 
> failures:
> 
>      # Auto-detecting system features: 2 libraries are missing. Try 'make VF=1' for a verbose list.
> 
> I.e. that way people can notice if the count goes up or down after an 
> update. Also, that too should be a single line, so that it does not 
> spam people.

ook

jirka
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