On Thu, Jun 30, 2016 at 12:01 PM, Jan Kratochvil <jan.kratochvil@xxxxxxxxxx> wrote: > On Thu, 30 Jun 2016 16:13:59 +0200, Josh Boyer wrote: >> On Thu, Jun 30, 2016 at 9:53 AM, Jan Kratochvil <jan.kratochvil@xxxxxxxxxx> wrote: >> > But now there is ppc64le for >=Power8. So <=Power7 can use ppc64 but newer >> >>=Power8 hardware does use ppc64le which is already Power8 optimized. >> > So isn't this problem (somehow temporarily) solved for now? >> >> POWER8 can run in either endian mode. So no, the problem is not solved. > > End-users do not even know what is endianity. And all application developers > need to write software BE/LE-independently (such as using ntohl()/htonl() > etc.) so they also do not care whether the host is BE or LE. Only <1% of > developers for high performance core or very low-end libraries (like glibc or > glib) need to care about BE/LE. > > So why to run Power8 in BE? Power is switching to LE AFAIK which makes it > also better compatible with buggy software ignoring BE/LE difference which is > (as all the software) targeting primarily x86* (=LE). It isn't switching. It's adding. I'd maybe agree that LE will become more prevalent over time, particularly as it is used in cloud workloads. However, BE mode isn't going away anytime soon. >> Realistically, it isn't about either specifically. Each iteration of >> POWER tends to require tuning specifically for that generation if you >> want to get the most performance out of your software. > > Latest CPU features get utilized mostly only in inner loops of high > performance code which should use IFUNC. So building the whole distro for the > latest CPU brings only incompatibility with no real performance advantage. > > > At least this is my expectation, the OP misses any real benchmark numbers > whether the distro build for the latest CPU generation is worth it. > IIRC for x86* it was not worth it. You might not be wrong, but you're dismissing the market dynamics of POWER that I mentioned. Those same dynamics lead to the distribution components for ppc64 being built as 64-bit binaries, even though at the time 32-bit binaries for 99% of packages were actually more than sufficient. Comparing performance numbers within POWER is fine, but applying the "this is how we do it in x86" logic isn't really suitable. They are different markets. I believe the markets will perhaps merge over time, but they clearly haven't yet today. josh -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://lists.fedoraproject.org/admin/lists/devel@xxxxxxxxxxxxxxxxxxxxxxx
