Re: [RFC 6/6] perf build: Introduce FEATURES_DUMP make variable

[Wangnan (F)]

On 2016/1/13 17:19, Jiri Olsa wrote:
> On Tue, Jan 12, 2016 at 05:28:28PM +0800, Wangnan (F) wrote:
>
> SNIP
>
> > For example:
> >
> > $ make feature-dump LDFLAGS="-static"
> >    BUILD:   Doing 'make -j24' parallel build
> >
> > Auto-detecting system features:
> > <SNIP>
> > ...                          zlib: [ on  ]
> > ...                          lzma: [ OFF ]     <--- looks good. I don't have
> > static lzma library
> > ...                     get_cpuid: [ on  ]
> > ...                           bpf: [ on  ]
> >
> >
> > $ make feature-dump
> >    BUILD:   Doing 'make -j24' parallel build
> >
> > Auto-detecting system features:
> > <SNIP>
> > ...                          zlib: [ on  ]
> > ...                          lzma: [ on  ]   <--- also good
> > ...                     get_cpuid: [ on  ]
> > ...                           bpf: [ on  ]
> >
> >
> > $ make feature-dump LDFLAGS="-static"
> >    BUILD:   Doing 'make -j24' parallel build
> >
> > Auto-detecting system features:
> > <SNIP>
> > ...                          zlib: [ on  ]
> > ...                          lzma: [ on  ]     <--- Bad...
> > ...                     get_cpuid: [ on  ]
> > ...                           bpf: [ on  ]
> >
> > Thank you.
> right, it's because feature is not under build framework and
> compilation does not care about flags change..
>
> I'll try to check on that.. does this patch help to improve
> the current speed or do you need to solve this to get substantial
> speedup?

I'm working on it. I have already done it, but still have some
problem. On some machine 'make_static' test target lost
'-liberty -lz' in its linker options. Seems something wrong in
this part:

ifeq ($(feature-libbfd), 1)
  EXTLIBS += -lbfd

  # call all detections now so we get correct
  # status in VF output
  $(call feature_check,liberty)
  $(call feature_check,liberty-z)
  $(call feature_check,cplus-demangle)

  ifeq ($(feature-liberty), 1)
    EXTLIBS += -liberty
  else
    ifeq ($(feature-liberty-z), 1)
      EXTLIBS += -liberty -lz
    endif
  endif
endif

On a 24 core machine the build-test takes about 16 mins. Faster than before:

real    16m7.642s
user    171m47.488s
sys    19m10.692s