On Tue, Jul 23, 2019 at 08:25:59AM -0400, Solomon Peachy wrote:
On Tue, Jul 23, 2019 at 11:05:59AM +0200, Kevin Kofler wrote:
> assume. And if you ask me, we should just stick to SSE2 as the baseline.
Ie the status quo.
> What are the big gains to be had from SSE3, SSSE3, SSE4.1, and SSE4.2?
Each of those individually, and from a general system library
persepective, I'd wager not a whole lot. But in aggregate, there are a
lot of Clear Linux benchmarks showing a sizeable bump in general purpose
That said -- A reasonable argument can be made to bump the baseline to
require SSE3, because all non-AMD x86_64 CPUs support it, and on the AMD
side, anything beyond their 1st-gen single-core K8s supports it.
(We're talking April 2005 here, versus the September 2003 introduction
of the very first x86_64 processor)
FWIW, in order to maintain historical guest ABI compatibility qemu
defaults to a CPU model, qemu64, that lacks sse3 support.
Most apps using libvirt (virt-install, virt-manager, OpenStack, oVirt,
etc) will override this historical default with something more modern.
So the QEMU default is only an issue for people who manually launch
QEMU without giving an explicit "-cpu" arg to pick something better.
Fortunately some work in QEMU upstream stands a good chance of letting us
move to a default CPU model that is more useful/modern in the not too
distant future (hopefully < 12 months)