On Sun, 2020-03-29 at 23:37 +1000, Allan McRae via arch-dev-public wrote:
On 29/3/20 11:17 pm, Filipe Laíns wrote:
I would also like to note that rebuilding everything with forced support for AVX2 or whatever won't have much effect. Most packages do not have workloads where it would make use sense to use these CPU extensions, and as such, GCC would not use them.
That assumes we just add AVX2. Whereas, requiring a CPU supporting AVX2 would bring other optimizations that would be used.
No, it should be true for all extensions.
As I replied earlier, AVX2 may be going too far. But is a good starting point for discussion. If that is too far, what could we accept? SSE4.2? AVX? Surely we can do better than pure x86_64.
No, SSE4.2 is too far. For me, the minimum should be AVX.
To have a separate architecture would require automated builds, which requires being able to sign packages automatically. And we have not achieved database signing in 9 years.... I'm looking for a boost that could be achieved now.
No, it would not. Where is this coming from? I already build split packages with SIMD instructions, I make the PKGBUILD build for 2 architectures instead with a minimal patch. If pacman is not able to handle parallel architectures, we should fix that. I think it's a valid use case. Furthermore, if you do indeed whish to move this forward please present us with reasonable data. Take a few packages that would benefit from this, build them with the proposed architecture and show us benchmarks. I think it's gonna be very hard for you to find packages with considerable improvement but I might be wrong, please show me. Filipe Laíns