Re: [Bug 350] New: i386 context switch very slow compared to 2.4 due to wrmsr (performance)

[Rob Landley <landley@trommello.org>]

On Thursday 13 February 2003 13:07, Andi Kleen wrote:
> [Hmm, this is becomming a FAQ]
>
> > Switching in and out of long mode is evil enough that I don't think it
> > is worth it.  And encouraging people to write good JIT compiling
>
> Forget it. It is completely undefined in the architecture what happens
> then. You'll lose interrupts and everything. Nothing for an operating
> system intended to be stable.
>
> I have no plans at all to even think about it for Linux/x86-64.
>
> > emulators sounds much better, especially in the long run.  But it can
> > be written.
>
> For DOS even a slow emulator should be good enough. After all most
> DOS Programs are written for slow machines. Bochs running on a K8
> will be hopefully fast enough. If not an JIT can be written, perhaps
> you can extend valgrind for it.

Fabrice Bellard, the author of TCC (Tiny C Compiler) seems to have taken it 
into his head that Bochs and Valgrind are too slow, and his current pet 
project is writing a new hand-optimized, portable JIT x86 emulator.  So 
there's one in the works already... :)

(See the tinycc-devel@nongnu.org archives for details, just this past weekend 
in fact...)

Rob

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