4 ms·
It's not a problem for SSE and AVX1. But, with AVX2/AVX-512, the deal is that you should not just dip your toe with an occasional call to a small SIMD task usi
by corysama 7y ago
It's not a problem for SSE and AVX1. But, with AVX2/AVX-512, the deal is that you should not just dip your toe with an occasional call to a small SIMD task using such heavy-hitting features. Either do enough SIMD work to overcome the down-clock, or use a lower-end SIMD functionality for smaller tasks.
And, even within AVX2/512 there are huge sets of added functionality that are really "AVX1-enhanced" without going wider. Those are fine to use to without worrying about downclocking.
- calaphos 7y agoThe AVX ALUs also go into power saving when not used and take a couple of cycles to switch back on, delaying the first AVX instruction. There is afaik even a paper on a side channel attack that uses this.