Re: [PATCH] perf util: Display warning when perf report/annotate is missing some libs

Arnaldo Carvalho de Melo
2018-03-23T14:50:54Z

Em Fri, Mar 23, 2018 at 11:09:03AM +0800, Jin, Yao escreveu:
> On 3/22/2018 4:51 PM, Jiri Olsa wrote:
> > On Thu, Mar 22, 2018 at 09:04:10AM +0800, Jin, Yao wrote:
> > > On 3/21/2018 11:38 PM, Jiri Olsa wrote:
> > > > On Wed, Mar 21, 2018 at 10:11:10AM +0800, Jin, Yao wrote:
> > > > > Hi Jiri,
> > > > >
> > > > > I'm still thinking it's worth displaying the warning when perf missing some
> > > > > libraries.
> > > > >
> > > > > Somebody just told me that perf didn't work well. While after some
> > > > > investigations, I found it's just missing some libraries when building the
> > > > > perf.
> > > > >
> > > > > But I have spent some time on getting the root cause. If with this patch, it
> > > > > should be very easily to know that.
> > > >
> > > > true.. Arnaldo, any feedback on this one?
> > > >
> > > > > > I just think it'd better provide some hints to user. For example,
> > > > > > "symbol is disabled and you need to install libelf/xxx", say something
> > > > > > like that.
> > > > > >
> > > > > > But it looks the column can't contain too much information (i.e. no more
> > > > > > space to contain the entire hints).
> > > > > >
> > > > > > Any idea? Or just add this warning in verbose mode?
> > > > > >
> > > > > > > also your change does not affect tui mode
> > > > > > >
> > > > > > > annotation for some reason does not start at all.. could be
> > > > > > > little more verbose ;-)
> > > > > > >
> > > > > > > jirka
> > > > > > >
> > > > > >
> > > > > > Yes, it doesn't affect tui mode.
> > > > > >
> > > > > > Or we just add this warning in verbose mode?
> > > > > >
> > > > > > e.g. perf report -v?
> > > >
> > > > how about displaying libraries separately with -vv output,
> > > > that would mimic the build message, like:
> > > >
> > > > $ ./perf -vv
> > > > perf version 4.16.rc6.g18fd48
> > > >
> > > > dwarf: [ on ]
> > > > dwarf_getlocations: [ on ]
> > > > glibc: [ on ]
> > > > gtk2: [ on ]
> > > > libaudit: [ on ]
> > > > libbfd: [ on ]
> > > > libelf: [ on ]
> > > > libnuma: [ on ]
> > > > numa_num_possible_cpus: [ on ]
> > > > libperl: [ on ]
> > > > libpython: [ on ]
> > > > libslang: [ on ]
> > > > libcrypto: [ on ]
> > > > libunwind: [ on ]
> > > > libdw-dwarf-unwind: [ on ]
> > > > zlib: [ on ]
> > > > lzma: [ on ]
> > > > get_cpuid: [ on ]
> > > > bpf: [ on ]
> > > >
> > > > and perf -vvv could display the 'make VF=1' info
> > > >
> > > > jirka
> > > >
> > >
> > > I'm just afraid that the newbie will not check the -vv on his own when he
> > > gets trouble in using perf.
> > >
> > > In other words, if a user is experienced and he knows -vv yet, I may assume
> > > that he should know installing all libraries before building the perf.
> > >
> > > This patch is specific for the perf newbie. It will directly shows the
> > > error/warning when the user launches the perf binary. It will have a little
> > > bit helps, I guess. :)
> >
> > I just don't like the idea that when you run perf report,
> > or annotate it spits out lines for every missing feature
> >
> > maybe we could detect missing features for given command
> > and display line about missing features and say something
> > like:
> >
> > 'Warning: symbol,dwarf support not compiled in (for more details run perf -vv)'
> >
> > or somwthing like that.. ;-)
> >
> > jirka
> >
>
> Hi Jiri,
>
> I think your idea is very good!
>
> I guess following it's just an example copied from perf building process,
> right?
>
> $ ./perf -vv
> perf version 4.16.rc6.g18fd48
>
> dwarf: [ on ]
> dwarf_getlocations: [ on ]
> glibc: [ on ]
> gtk2: [ on ]
> libaudit: [ on ]
> libbfd: [ on ]
> libelf: [ on ]
> libnuma: [ on ]
> numa_num_possible_cpus: [ on ]
> libperl: [ on ]
> libpython: [ on ]
> libslang: [ on ]
> libcrypto: [ on ]
> libunwind: [ on ]
> libdw-dwarf-unwind: [ on ]
> zlib: [ on ]
> lzma: [ on ]
> get_cpuid: [ on ]
> bpf: [ on ]
>
> We can check some CFLAGS like "#ifdef HAVE_XXX" in perf code to determine if
> some libraries are compiled in.
>
> For example,
>
> #ifdef HAVE_LIBNUMA_SUPPORT
> printf("libnuma: [ on ]");
> #endif
>
> For some features, such as "numa_num_possible_cpus", which doesn't have
> CFLAGS variables. Maybe we can ignore them in report?
>
> I'd like to upgrade my patch to support perf -vv.

Please go ahead! :-) We're all on the same page now, I think.

- Arnaldo