Comment by IshKebab
7 hours ago
Sure, it's not just the support though. As I understand it it also has serious power and frequency implications. Also if your process uses AVX-512 you suddenly have an extra 2kB of data to save/restore on context switches. Maybe not super significant but I really doubt this will ever make it into standard libraries.
AVX-512 increases energy efficiency and performance unconditionally, in all AMD Zen 4 and later CPUs and in all Intel Ice Lake and later CPUs.
Only in the now obsolete Intel server and workstation CPUs from the Skylake Server, Cascade Lake and Cooper Lake families, using AVX-512 was a win when a great number of vector instructions were executed, but it was a loss when only a small number of vector instructions were executed.
This was caused by a really stupid Intel voltage and frequency controller, which could not react quickly enough to changes in power consumption. Because of this, it dropped preemptively the clock frequency, before there was any need for this, for fear that the CPU will overheat if the power consumption will increase in the future and the voltage/frequency controller will not be able to decrease it fast enough, before reaching the temperature limit. For the same reason, the clock frequency was kept low a very long time after the last vector instruction seen.
Now this is pretty much history, because few have kept those 7 to 10 years old inefficient servers and those who have kept them normally run workloads that either use a lot of vector instructions or they do not use such instructions.
Nowadays the only reason for not using AVX-512 is when the software is intended to be widely used and one does not want to distribute 2 versions, one with AVX-512 for AMD or P-core Intel CPUs and one with AVX for E-core or hybrid Intel CPUs or very old AMD CPUs.