On Wed, Sep 28, 2022 at 12:14:07AM +0200, Michal Suchánek wrote:
And that's the thing: for vast majority of code being able to run it a few % faster makes absolutely no difference for vast majority of use cases.
And for a lot of code it would be great to run it faster but the bottleneck is not the CPU so the new instructions don't really help.
Whilst not wanting to dead-end lots of very serviceable hardware, should be careful about not exploiting newer features too. Findings presented at a power conference by Intel a few years ago (seen similar from others too) was the benefit of doing things as quickly as possible, then diving into a low-power mode and/or shutting down subsystems of the chip.
One might think "who cares about power-saving? This system's not a laptop/embedded/sensor etc", but inefficient work gets turned into heat, which then requires further management - one of our colos has charged us per U (rackspace), per GiB (bandwidth) and per W (thermal cost of aircon) for two decades; which was an unusual pricing structure at the outset. Seemingly marginal gains do add up over time.
Full disclosure, our company collaborated on further research to instrument a system and see if power optimisations could be written into gcc/a compiler. Initially it was an immense project, similar to "extracting a decagram of myelin from 4 tons of earth worms".