> -----Original Message----- > From: Michael Stone [mailto:mst...@debian.org] > Sent: sexta-feira, 3 de fevereiro de 2017 11:38 > To: Gustavo Serra Scalet <gustavo.sca...@eldorado.org.br> > Cc: 854...@bugs.debian.org; coreut...@gnu.org > Subject: Re: Bug#854053: coreutils: improve 2x-3x sha256sum performance > on ppc64le due to current gcc optimization bug > > On Fri, Feb 03, 2017 at 11:22:28AM -0200, Gustavo Serra Scalet wrote: > >The sha256sum provided by coreutils (without openssl) is performing > >poorly with versions >= 4.9 until 7.0 (currently under development). > >The reason for that is the -fschedule-insns optimization that is used > >with -O2. By simply deactivating it, there is a performance improvement > >of > >2 to 3 times. > > > >I'm attaching a patch that demonstrate that behavior but it lacks this > >condition: > >* If ppc64le > >* If gcc being used is >= 4.9 and < 7.0 > > > >Notes: > >1) gcc-7 is not affected by this bug (verified on 20170129 snapshot). > >2) clang is not affected by this bug (verified on v3.8 and v3.9). > >3) strangely the sha512 is not affected by this. > > Sounds good in theory, just needs conditionals. :) For debian we can > just assume the compiler version and remove the patch when a newer > compiler is available as a dependency, but making it conditional on ppc > seems essential. Upstream would probably want some kind of compiler > based test.
Seems good to me. > My understanding is that just adding this option to cflags > when building on the appropriate architecture wouldn't work, because it > would negatively impact other code, is that correct? Yes, I wouldn't add this CFLAG for the whole package, but only for the lib/sha256.o target (that's what my patch is doing). For that target, I see a better performance without that optimization than with it. Normally nobody shuts off optimization to improve performance but, as I said, it is a bug that happens on this target and it affects gcc versions >= 4.9 and < 7.0. If you see a different way out, or a more neat approach, please advise. > > Mike Stone > > (additional context quoted below) > > >Below a demonstration of how it performs: > > > >=================================================== > >$ (./configure && make -j9) > /dev/null && time src/sha256sum > >~/ubuntu-16.10-server-ppc64el.iso > >configure: WARNING: libacl development library was not found or not > usable. > >configure: WARNING: GNU coreutils will be built without ACL support. > >configure: WARNING: libattr development library was not found or not > usable. > >configure: WARNING: GNU coreutils will be built without xattr support. > >configure: WARNING: libcap library was not found or not usable. > >configure: WARNING: GNU coreutils will be built without capability > support. > >configure: WARNING: libgmp development library was not found or not > usable. > >configure: WARNING: GNU coreutils will be built without GMP support. > >src/who.c: In function 'print_user': > >src/who.c:454:20: warning: initialization discards 'const' qualifier > from pointer target type [-Wdiscarded-qualifiers] > > int *a = utmp_ent->ut_addr_v6; > > ^~~~~~~~ > >d14bdb413ea6cdc8d9354fcbc37a834b7de0c23f992deb0c6764d0fd5d65408e > >/home/gut/ubuntu-16.10-server-ppc64el.iso > > > >real 0m18.670s > >user 0m16.566s > >sys 0m0.745s > > > >$ # now with the following patch: > >$ diff Makefile.in ../Makefile.in > >8989c8989 > >< @am__fastdepCC_TRUE@ $(COMPILE) -MT $@ -MD -MP -MF $$depbase.Tpo -c > >-o $@ $< &&\ > >--- > >> @am__fastdepCC_TRUE@ $(COMPILE) $$([ "$@" == "lib/sha256.o" ] && > >> echo "-fno-schedule-insns") -MT $@ -MD -MP -MF $$depbase.Tpo -c -o $@ > >> $< &&\ > >$ cp ../Makefile.in Makefile.in > >$ (./configure && make -j9) > /dev/null && time src/sha256sum > >~/ubuntu-16.10-server-ppc64el.iso > >configure: WARNING: libacl development library was not found or not > usable. > >configure: WARNING: GNU coreutils will be built without ACL support. > >configure: WARNING: libattr development library was not found or not > usable. > >configure: WARNING: GNU coreutils will be built without xattr support. > >configure: WARNING: libcap library was not found or not usable. > >configure: WARNING: GNU coreutils will be built without capability > support. > >configure: WARNING: libgmp development library was not found or not > usable. > >configure: WARNING: GNU coreutils will be built without GMP support. > >src/who.c: In function 'print_user': > >src/who.c:454:20: warning: initialization discards 'const' qualifier > from pointer target type [-Wdiscarded-qualifiers] > > int *a = utmp_ent->ut_addr_v6; > > ^~~~~~~~ > >d14bdb413ea6cdc8d9354fcbc37a834b7de0c23f992deb0c6764d0fd5d65408e > >/home/gut/ubuntu-16.10-server-ppc64el.iso > > > >real 0m5.903s > >user 0m5.560s > >sys 0m0.255s > > >--- Makefile.in 2016-11-30 16:34:55.000000000 -0200 > >+++ ../Makefile.in 2017-02-03 09:33:17.936000000 -0200 > >@@ -8986,7 +8986,7 @@ > > > > .c.o: > > @am__fastdepCC_TRUE@ $(AM_V_CC)depbase=`echo $@ | sed > 's|[^/]*$$|$(DEPDIR)/&|;s|\.o$$||'`;\ > >-@am__fastdepCC_TRUE@ $(COMPILE) -MT $@ -MD -MP -MF $$depbase.Tpo -c > -o $@ $< &&\ > >+@am__fastdepCC_TRUE@ $(COMPILE) $$([ "$@" == "lib/sha256.o" ] && echo > >+"-fno-schedule-insns") -MT $@ -MD -MP -MF $$depbase.Tpo -c -o $@ $< > >+&&\ > > @am__fastdepCC_TRUE@ $(am__mv) $$depbase.Tpo $$depbase.Po > > @AMDEP_TRUE@@am__fastdepCC_FALSE@ $(AM_V_CC)source='$<' object='$@' > libtool=no @AMDEPBACKSLASH@ > > @AMDEP_TRUE@@am__fastdepCC_FALSE@ DEPDIR=$(DEPDIR) $(CCDEPMODE) > $(depcomp) @AMDEPBACKSLASH@
