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Date: Tue, 17 Dec 2002 11:54:01 -0800
From: "H. Peter Anvin" <hpa@transmeta.com>
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CC: Alan Cox <alan@lxorguk.ukuu.org.uk>, Ulrich Drepper <drepper@redhat.com>,
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Subject: Re: Intel P6 vs P7 system call performance
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Richard B. Johnson wrote:
> 
> You can call intersegment with a full pointer. I don't know how
> expensive that is. Since USER_CS is a fixed value in Linux, it
> can be hard-coded
> 
> 		.byte 0x9a
> 		.dword 0xfffff000
> 		.word USER_CS
> 
> No. I didn't try this, I'm just looking at the manual. I don't know
> what the USER_CS is (didn't look in the kernel) The book says the
> pointer is 16:32 which means that it's a dword, followed by a word.
> 

It's quite expensive (not as expensive as INT, but not that far from
it), and you also push CS onto the stack.

	-hpa


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