Messages in this thread | | | Date | Mon, 1 Jun 1998 16:08:38 +0200 | From | Martin Mares <> | Subject | Re: Compatible with i386/UP but optimised for i686/SMP [was Re: test_and_set_bit() not atomic forever?] |
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Hi,
> > >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.
You cannot avoid significant slowdown with SMP kernel on UP machines due to extra locking needed.
> Or a sysadmin, in a situation where managing different kernels for that > extra bit of efficiency isn't worth the administrative overhead.
When you need to have a single kernel for lots of similar machines, they are usually UP, so compiling a SMP kernel doesn't make sense.
> 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?)
It would make sense to distribute three kernels:
- i386
- i586
- i586 SMP
Have a nice fortnight -- Martin `MJ' Mares <mj@ucw.cz> http://atrey.karlin.mff.cuni.cz/~mj/ Faculty of Math and Physics, Charles University, Prague, Czech Rep., Earth "The computer is mightier than the pen, the sword, and usually, the programmer."
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