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

From: Andi Kleen (
Date: Wed Feb 12 2003 - 05:45:08 EST

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

I would like to have fast context switch on IA32 though so it would be nice
if someone deeply familiar with sys_vm86 could review my patch.

Avoiding the SYSCALL_CS MSR is independent from the issues Linus raised.

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