Am 07.11.2015 um 19:01 schrieb Kevin Kofler:
Reindl Harald wrote:
well, who's to say that we stay forever on a level of CPU
feature-support while there are instruction sets available for a whole
decade which improve performance, save power in case you need fewer
instructions doing the same work?
not that i say Fedora should go ahead and build with -mavx but a
discussion about SSE3 in 2015 is really odd
Sorry, but hardware simply does not get replaced instantly. This is a matter
of both:
* cost – hardware is not free (as in beer)
that *really* depends
these days (and i talk about hardware from 2011) you can virtualize things fast, easy and efficient and consolidate machines on more or less cheap hardware
besides it brings new CPU capabilities it saves a lot of energy:
* one machine instead 2,3,4 or 10 machines
* the new hardware needs so much less power
* your UPS (in case you use one) can be cheaper or lasts longer
* cooling is easier, cheaper and not that loud
some numbers in that context:
in early 2010 we planned a UPS systems to last for around 3 hours, with the current hardware and after consolidation the same UPS lasts 9 hours now and the air conditioner has lower load and longer lifetime
the same applies to consumer hardware, my 365/7 running homeserver from 2011 is a power beast and the whole IT needs around 50W while the previous hardware needed 120W - that's money, that's heat on summer days, that's less noise and hardddisks don't need to replaced that often because they are cooler
* ecology – there are huge landfills in China, India and Africa full of
electronic trash from Europe and the USA; that gets mined for
recyclable materials in an extremely polluting way that not only
ruins the environment, but also damages the health of the people
doing the mining (and the most dangerous materials are handled
by children). Materials used for electronic components are
precious, someone has to recycle them or they would run out
pretty soon.
that is true but see above
As a developer who writes mathematical software for a living, I'd love being
able to require AVX-512 right now (https://en.wikipedia.org/wiki/AVX-512 –
finally a way to specify the rounding mode per operation
(https://en.wikipedia.org/wiki/EVEX_prefix) rather than through the
extremely expensive stateful fesetround operations that reset the whole
prefetch queue, interval arithmetic should become MUCH faster with that),
but I have to deal with real-world CPUs that are here NOW (so it might make
sense to have runtime detection for AVX-512 only in 1 or 2 years, and
requiring it is simply not possible within the next decade)
maybe you did not get "not that i say Fedora should go ahead and build with -mavx" but we talk about SSE3
talking about a rapid moving distribution like Fedora and at the same time hestitate to use technology available for a decade is strange - i guess people plan to run their hardware for 10, 12, 15 years are not using typically a distribution like Fedora
The flip side of it is that Fedora is the foundation for RHEL and other distributions. Most of the others don't matter so much, but RHEL does, as that has to support servers and such. But even there, I would suggest to say that we could say that RHEL 8 shouldn't have a problem bumping up, since RHEL 7 supports those systems fine and will be supported for 9 more years.
真実はいつも一つ！/ Always, there's only one truth!
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