Intel’s 512-bit AVX-512 SIMD extensions for x86 instruction set architecture are used for various compute-intensive workloads on workstations and servers, but AVX-512 hardware execution units are power hungry and that causes some headaches for developers.
Software icon Linus Torvalds recently condemned AVX-512 and called the company to develop a better solution for complex HPC problems. The creator of Linux went as far as called AVX-512 a ‘power virus’ and wished it to ‘die a painful death.’
Intel’s Advanced Vector Extensions are meant to radically improve performance in workloads that rely on floating point computations. HPC programs and various FP benchmarks that use AVX-512-optimized code offer tangibly better performance than applications which rely purely on FPUs. However, AVX-512 units lower CPU clocks because of significant power draw.
“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,” Torvalds said.
“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.”
Torvalds added that he believed Intel should spend CPU transistor budget on regular FPUs or on GPUs rather than on AVX-512 units because the former can benefit everyone, whereas only select applications can take advantage of AVX-512.
“I want my 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),” Mr. Torvalds exclaimed.
Intel does not support all AVX-512 instructions across all of its processors. Server CPUs support the extensions broadly as many HPC workloads use Intel’s latest extensions, but client processors until recently supported only select AVX-512 instructions. Meanwhile, Intel’s latest Ice Lake chips and upcoming Tiger Lake CPUs support AVX-512 rather extensively as the chipmaker hopes that developers of client software will also take advantage of the technology.
It is necessary to note that Linus Torvalds is not against extensions for x86 instruction set architecture per se, but he says that AVX2 is more than enough.
“I absolutely detest FP benchmarks, and I realize other people care deeply,” said Mr. Torvalds. “I just think AVX-512 is exactly the wrong thing to do. […] 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 an FPU that is barely good enough on the side, and people will be happy. AVX2 is much more than enough.”