Re: /shared questions

Nicholas E. Walker writes:
> How does one represent optimizations?  Is /shared/syst/linux-i686 valid?

You can, of course, have a 386-architecture OS for your 386 machines,
and a 686-architecture OS for your 686 machines. Then the 686 binaries
can take advantage of extra features of the 686 architecture, and can be
optimized differently.

The backwards compatibility of 386 with 686 means that you could also
have them sharing a 386-architecture OS. That saves space, of course,
but it also means that your binaries can't take advantage of the 686,
and can't be optimized separately for the 386 and 686.

The package manager needs to know your decision so that it can set up
appropriate symlinks from /package to /shared. The decision should also
be communicated somehow to compilers (and similar packages), so that
they can automatically take advantage of the 686 in the first case but
avoid it in the second. Typical packages that simply use the compiler
won't have to worry about any of this.

Similar comments apply to aspects of OS architecture other than the
hardware architecture.

---D. J. Bernstein, Associate Professor, Department of Mathematics,
Statistics, and Computer Science, University of Illinois at Chicago