On Mon, Sep 30, 2013 at 06:42:10PM +0200, Ingo Molnar wrote: > > This series (with combo patch attached) implements (much) faster > perf-tools feature-auto-detection. > > I used 3 tricks to implement feature auto-dependencies and to speed up > feature detection: > > - standalone Makefile in config/feature-checks/ built in parallel > > - split-out standalone .c files in config/feature-checks/*.c > > - used GCC's auto-dependency generation feature (-MD) to track the > effects of system library addition/removal. > > Before the changes a fully cached re-build of an already built tree took > 2.6 second: > > $ perf stat --null --sync --repeat 3 -a make Makefile > > 2.669467209 seconds time elapsed > ( +- 0.07% ) > > After the changes it takes only 0.6 seconds: > > 0.599161560 seconds time elapsed > ( +- 0.25% )
nice! > > So the empty build got 4.4x faster. > SNIP > ifdef NO_DEMANGLE > CFLAGS += -DNO_DEMANGLE > else > - ifdef HAVE_CPLUS_DEMANGLE > + ifdef HAVE_CPLUS_DEMANGLE_SUPPORT > EXTLIBS += -liberty > - CFLAGS += -DHAVE_CPLUS_DEMANGLE > + CFLAGS += -DHAVE_CPLUS_DEMANGLE_SUPPORT > else > FLAGS_BFD=$(CFLAGS) $(LDFLAGS) $(EXTLIBS) -DPACKAGE='perf' -lbfd > - has_bfd := $(call try-cc,$(SOURCE_BFD),$(FLAGS_BFD),libbfd) > - ifeq ($(has_bfd),y) > + ifeq ($(feature-libbfd), 1) > EXTLIBS += -lbfd > else > FLAGS_BFD_IBERTY=$(FLAGS_BFD) -liberty > @@ -388,7 +410,7 @@ else > has_cplus_demangle := $(call > try-cc,$(SOURCE_CPLUS_DEMANGLE),$(FLAGS_CPLUS_DEMANGLE),demangle) > ifeq ($(has_cplus_demangle),y) > EXTLIBS += -liberty > - CFLAGS += -DHAVE_CPLUS_DEMANGLE > + CFLAGS += -DHAVE_CPLUS_DEMANGLE_SUPPORT > else > msg := $(warning No bfd.h/libbfd found, install > binutils-dev[el]/zlib-static to gain symbol demangling) > CFLAGS += -DNO_DEMANGLE > @@ -400,30 +422,29 @@ else > endif Why not add tests for has_bfd_iberty/has_bfd_iberty_z/has_cplus_demangle? We could remove the config/feature-tests.mak completely and other cleanup like remove try-cc. jirka -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
