Re: Intel P6 vs P7 system call performance

[H. Peter Anvin]

Ingo Molnar wrote:
> On Tue, 24 Dec 2002, Linus Torvalds wrote:
> 
> 
>>I realized that there is really no reason to use __KERNEL_DS for this,
>>and that as far as the kernel is concerned, the only thing that matters
>>is that it's a flat 32-bit segment. So we might as well make the kernel
>>always load ES/DS with __USER_DS instead, which has the advantage that
>>we can avoid one set of segment loads for the "sysenter/sysexit" case.
> 
> 
> this basically hardcodes flat segment layout on x86. If anything (Wine?)
> modifies the default segments, it can wrap syscalls by saving/restoring
> the modified %ds and %es selectors explicitly.
> 

I don't think you can modify the GDT segments.

	-hpa

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