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List:       linux-kernel
Subject:    Re: [Bug 350] New: i386 context switch very slow compared to 2.4 due to wrmsr (performance)
From:       ebiederm () xmission ! com (Eric W !  Biederman)
Date:       2003-02-13 5:17:21
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Andi Kleen <ak@suse.de> writes:

> On Wed, Feb 12, 2003 at 10:27:41AM +0000, Jamie Lokier wrote:
> > Andi Kleen wrote:
> > > +	/* FIXME should disable preemption here but how can we reenable it? */
> > > +
> > > +	enable_sysenter();
> > > +
> > 
> > Try this:
> 
> [...] I have no real interest in vm86 mode, perhaps one of the people
> interested in dosemu etc. could take care of it. I'm very glad it doesn't
> exist on my main architecture - x86-64 - given how many hacks it needs to be 
> supported.

There is certainly some old cruft in there, but...

I have been thinking evil thoughts lately about what it would take
to implement on x86-64.

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
emulators sounds much better, especially in the long run.  But it can
be written.

Eric
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