Re: glibc recompile - optimized for G5 cpu target

Peter,

I wish I had a good answer for you regarding relevant and useful benchmark tools,but I just wanted to add that I would like to try and do the same thing for PPC G4 machines using their architecture specific compilation flags as well to see what difference it makes. I'll report back on my success/failure as well. If you do come across a good tool for comparing performance between the two, let me know. I'll be using the CFLAGS under the G4 section on this Gentoo Wiki page: https://wiki.gentoo.org/wiki/Safe_CFLAGS

As we have discussed before, it would great to squeeze every last bit of efficiency as we can out of these older machines. I also enjoyed your comment from a post here a week or so ago about using an non Intel/AMD machine to learn Linux. I couldn't agree more. :)

Thanks,

Brock

On Wed, Jan 6, 2016 at 5:02 PM, Peter Saisanas <psaisanas@gmail.com> wrote:

Hi,

Ok, i have modified the debian rules file for glibc 2.21-6 and recompiled.

I have built this package essentially with the cflags: -O3 together with the following extra line below:
extra_cflags = -mcpu=G5 -mtune=G5 -maltivec -mabi=altivec

Ill be the first to admit that i haven't played around with glibc before.
Not sure if this will even make any difference, just wanted to try an experiment for myself.

It compiles, runs through the tests and builds the packages.
The build logs are approximately 13MB each for powerpc and powerpc64!

The following log files in the build-tree test-results-powerpc64-linux-gnu-ppc64 & test-results-powerpc-linux-gnu-libc both came up with no logged testsuite failures. I assume these logs are where to look for obvious testsuite regressions?

After compilation, I have the following deb packages:
glibc-doc_2.21-6+local-g5.1_all.deb
glibc-source_2.21-6+local-g5.1_all.deb
libc6_2.21-6+local-g5.1_powerpc.deb
libc6-dbg_2.21-6+local-g5.1_powerpc.deb
libc6-dev_2.21-6+local-g5.1_powerpc.deb
libc6-dev-ppc64_2.21-6+local-g5.1_powerpc.deb
libc6-pic_2.21-6+local-g5.1_powerpc.deb
libc6-ppc64_2.21-6+local-g5.1_powerpc.deb
libc6-ppc64-dbgsym_2.21-6+local-g5.1_powerpc.deb
libc6-udeb_2.21-6+local-g5.1_powerpc.udeb
libc-bin_2.21-6+local-g5.1_powerpc.deb
libc-bin-dbgsym_2.21-6+local-g5.1_powerpc.deb
libc-dev-bin_2.21-6+local-g5.1_powerpc.deb
libc-dev-bin-dbgsym_2.21-6+local-g5.1_powerpc.deb
libc-l10n_2.21-6+local-g5.1_all.deb
libnss-dns-udeb_2.21-6+local-g5.1_powerpc.udeb
libnss-files-udeb_2.21-6+local-g5.1_powerpc.udeb
locales_2.21-6+local-g5.1_all.deb
locales-all_2.21-6+local-g5.1_powerpc.deb
multiarch-support_2.21-6+local-g5.1_powerpc.deb
nscd_2.21-6+local-g5.1_powerpc.deb
nscd-dbgsym_2.21-6+local-g5.1_powerpc.deb

I have installed the recompiled glibc on a spare hdd with an older install of Debian and the installation still seems to have survived (actually surprised me more than anything else)!

I'm not expecting miracles (or anything positive TBH) but would lmbench be an appropriate benchmark to run to compare the performance of glibc (i.e. original Debian 2.21-6 vs 2.21-6 with G5 cflags) or any other benchmark recommendations?

I know, i know.... This is unsupported!

Regards,
Peter