According to a mailing list post spotted by Phoronix, Linux creator Linus Torvalds has shared his strong views on the AVX-512 instruction set. The discussion arose as a result of recent news that Intel's upcoming Alder Lake processors reportedly lack support for AVX-512.
Torvalds' advice to Intel is to focus on things that matter instead of wasting resources on new instruction sets, like AVX-512, that he feels aren't beneficial outside the HPC market.
AVX-512 support debuted in Intel's Xeon Phi x200 (codename Knights Landing) processor in 2016. However, the instruction set later made its way into the chipmaker's other offerings, such as Skylake-SP, Skylake-X, Cannon Lake and Cascade Lake. Currently, Intel's both Cooper Lake and Ice Lake processors support certain AVX-512 subsets. While Alder Lake seemingly lacks AVX-512, the chipmaker has confirmed that Tiger Lake will exploit the instruction set.
We've included a copy of Linus Torvalds' opinion on AVX-512 below:
I hope AVX512 dies a painful death, and that Intel starts fixing real problems instead of trying to create magic instructions to then create benchmarks that they can look good on.
I hope Intel gets back to basics: gets their process working again, and concentrate more on regular code that isn't HPC or some other pointless special case.
I've said this before, and I'll say it again: in the heyday of x86, when Intel was laughing all the way to the bank and killing all their competition, absolutely everybody else did better than Intel on FP loads. Intel's FP performance sucked (relatively speaking), and it matter not one iota.
Because absolutely nobody cares outside of benchmarks.
The same is largely true of AVX512 now - and in the future. Yes, you can find things that care. No, those things don't sell machines in the big picture.
And AVX512 has real downsides. I'd much rather see that transistor budget used on other things that are much more relevant. Even if it's still FP math (in the GPU, rather than AVX512). Or just give me more cores (with good single-thread performance, but without the garbage like AVX512) like AMD did.
I want my power limits to be reached with regular integer code, not with some AVX512 power virus that takes away top frequency (because people ended up using it for memcpy!) and takes away cores (because those useless garbage units take up space).
Yes, yes, I'm biased. I absolutely destest FP benchmarks, and I realize other people care deeply. I just think AVX512 is exactly the wrong thing to do. It's a pet peeve of mine. It's a prime example of something Intel has done wrong, partly by just increasing the fragmentation of the market.
Stop with the special-case garbage, and make all the core common stuff that everybody cares about run as well as you humanly can. Then do a FPU that is barely good enough on the side, and people will be happy. AVX2 is much more than enough.
Yeah, I'm grumpy.
Linus
Torvalds, who was once an Intel user, recently saw the light and crossed over to the Red Team. His Ryzen Threadripper 3970X accelerated his workloads by threefold.
