On Mon, Jul 22, 2019 at 02:51:27PM -0400, Ben Cotton wrote: > After preliminary discussions with CPU vendors, we propose AVX2 as the > new baseline. AVX2 support was introduced into CPUs from 2013 to > 2015. See [https://en.wikipedia.org/wiki/Advanced_Vector_Extensions#CPUs_with_AVX2 > CPUs with AVX2]. While one can make a reasonable argument to bump the baseline to something newer than the very first K8 implmentation, jumping all the way up to AVX2 is insane, because it will render Fedora useless on all but the most recent generations of CPUs. Because _introduced_ is long, long way from _deployed_. Even today Intel continues to sell modern-but-non-AVX-capable CPUs under their Pentium and Celeron brands. Are we going to exclude all of those too? As an example, of the what, dozen or so systems I have Fedora installed on today, only one supports AVX2. Three of them don't even support AVX1 (AMD 10h and 14h). This means that come Fedora 32, I'll be faced with the choice of replacing nearly every bit of kit I own. But since anectdote != data, are there any sort of deployment numbers out there that show how many Fedora deployments are on AVX[2]-capable hardware? > Fedora will use current CPUs more efficiently, increasing performance > and reducing power consumption. I think we need to see some actual benchmarks demonstrating this. For the core kernel and system libraries rather than microbenchmarks or specific applications that already sport AVX[2] codepaths. BTW, it wasn't until mid-late-2018 that AAA games started to require AVX1. > Moreover, when Fedora is advertised as a distribution by a compute > service provider, users can be certain that their AVX2-optimized > software will run in this environment. So.. hosting providers and their users are now the sole Fedora audience? > * Other developers: Other developers may have to adjust test suites > which expect exact floating point results, and correct linking with > <code>libatomic</code>. They will also have to upgrade their x86-64 > machines to something that can execute AVX2 instructions. Yeah, "they just have to upgrade their systems". - Solomon -- Solomon Peachy pizza at shaftnet dot org High Springs, FL ^^ (email/xmpp) ^^ Quidquid latine dictum sit, altum videtur.
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