Monday, 13 July 2020 08:56

Torvalds hopes Intel's AVX-512 extensions die a painful death

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Linus Torvalds: "Stop with the special-case garbage, and make all the core common stuff that everybody cares about run as well as you humanly can." Linus Torvalds: "Stop with the special-case garbage, and make all the core common stuff that everybody cares about run as well as you humanly can." Courtesy YouTube

Linux creator Linus Torvalds has expressed the hope that Intel's newly released AVX-512 extensions would "die a painful death" adding that the company should start "fixing real problems instead of trying to create magic instructions to then create benchmarks that they can look good on".

AVX-512 is a set of 512-bit extensions to the 256-bit Advanced Vector Extensions SIMD instructions for the x86 instruction set arhcitecture which was proposed by Intel seven years ago, according to Wikipedia.

These instructions were implemented in Intel's Xeon Phi x200 and Skylake-X CPUs, including the Core-X series, as well as the new Xeon Scalable Processor Family and Xeon D-2100 Embedded Series.

In a mailing list post, Torvalds said he hoped Intel would return to basics, get their process working again and focus more on regular code that was not HPC (high performance computing) or any 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 (floating point) loads," he said. "Intel's FP performance sucked (relatively speaking), and it mattered not one iota. Because absolutely nobody cares outside of benchmarks.

"The same is largely true of AVX-512 now - and in the future. Yes, you can find things that care. No, those things don't sell machines in the big picture.

"And AVX-512 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 AVX-512). Or just give me more cores (with good single-thread performance, but without the garbage like AVX-512) like AMD did."

In May, Torvalds said publicly that he had switched from an Intel-based desktop to an AMD-based one. In a post about the release of the 5.7-rc7 kernel, hesaid: "In fact, the biggest excitement this week for me was just that I upgraded my main machine, and for the first time in about 15 years, my desktop isn't Intel-based.

"No, I didn't switch to ARM yet, but I'm now rocking an AMD Threadripper 3970x. My 'allmodconfig' test builds are now three times faster than they used to be, which doesn't matter so much right now during the calming down period, but I will most definitely notice the upgrade during the next merge window. "

In his post about AVX-512, Torvalds said he wanted his power limits to be reached with regular integer code, not with "some AVX-512 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)".

He admitted that his view was biased. "I absolutely detest FP benchmarks, and I realise other people care deeply. I just think AVX-512 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."

And he added, as an afterthought, "Yeah, I'm grumpy."


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Sam Varghese

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Sam Varghese has been writing for iTWire since 2006, a year after the site came into existence. For nearly a decade thereafter, he wrote mostly about free and open source software, based on his own use of this genre of software. Since May 2016, he has been writing across many areas of technology. He has been a journalist for nearly 40 years in India (Indian Express and Deccan Herald), the UAE (Khaleej Times) and Australia (Daily Commercial News (now defunct) and The Age). His personal blog is titled Irregular Expression.

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