25th August 2018, 2 min read

AVX-512 throttling: heavy instructions are maybe not so dangerous

Travis Downs says:

August 25, 2018 at 6:12 am

Note that heavy/light applies to both AVX2 and AVX-512.

So for example heavy AVX2 is in principle the same thing as light AVX-512 (best to show in a chart).

However, the same “heavy doesn’t necessarily mean heavy unless you do it a lot” thing you discuss in this post applies to AVX2 heavy instructions, which in fact makes them quite different than AVX-512 light: because AVX-512 light take effect immediately as soon as one occurs (as far as I can tell), but AVX2 heavy need to be run a lot. So in practice, AVX2 heavy is lets you run one speed tier higher (the highest tier, in fact) compared to AVX-512 light.
1. Travis Downs says:
  
  August 25, 2018 at 6:13 am
  
  So in practice, AVX2 heavy is lets you run one speed tier higher (the
  highest tier, in fact) compared to AVX-512 light.
  
  That should read “… AVX2 heavy often lets you run one speed tier higher…”.
Royi says:

August 25, 2018 at 11:38 am

Nice forum thread on the subject:

https://www.realworldtech.com/forum/?threadid=179654&curpostid=179715