Compatible with i386/UP but optimised for i686/SMP [was Re: test_and_set_bit() not atomic forever?]

Jamie Lokier (lkd@tantalophile.demon.co.uk)
Mon, 1 Jun 1998 11:54:48 +0100


On Mon, Jun 01, 1998 at 09:27:00AM +0100, Philip Blundell wrote:
> >The point was that lots of people are running SMP kernels on UP machines,
> >where it's gratuitous overhead.
>
> Then they shouldn't do that.

Unless they're a distributor who wants to run one kernel per
architecture, + modules.

Or a sysadmin, in a situation where managing different kernels for that
extra bit of efficiency isn't worth the administrative overhead.

These points apply also to the i386/i486/i586/i686 optimisation issue.
Is it worth making a kernel nearly optimised for i686 but compatible
with i386? (Perhaps using fixups in the same way to blank out calls to
do the "verify put_user" type stuff, vs. blanking out flush_tlb and so
forth?)

-- Jamie

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