Subject: Re: new sysctl: hw.cpu_isa
To: Chris G. Demetriou <>
From: Allen Briggs <>
List: tech-kern
Date: 11/14/2000 14:06:38
On Tue, Nov 14, 2000 at 09:25:40AM -0800, Chris G. Demetriou wrote:
> You don't want to optimize libraries, and select them, based on CPU,
> at least for the Alpha architecture.
> You want to pick which CPU features are meaningful to performance of
> various libraries, and then compile and select based on them.

So (assuming that there is enough to be gained from doing this,
which it seems there may well be for some archs) instead of
hw.cpu_isa, it sounds like you really want to abstract from the
ISA to a set of optimizations.

This leads me to consider something more like a hw.cpu_optimization_type
(or whatever) that would have a MACHINE_ARCH-specific set of values.
This could be set based on the CPU's model, the CPU's capability
set (if separate from the model), and whatever else (e.g., a GENERIC
or INSTALL kernel might set it to a conservative value if there's
any chance that a dangerous choice could be made).