Re: Intel P6 vs P7 system call performance

H. Peter Anvin
2002-12-17T19:46:36Z

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