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DateWed, 13 Sep 2006 11:59:42 +0200
FromIngo Molnar <>
SubjectRe: i386 PDA patches use of %gs
* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> [...]  The basic inner loop is:
> 
> 	push %segreg
> 	mov  %selectorreg, %segreg
> 	add  $1,%segreg:offset	# use the segment register
> 	pop  %segreg

well, the most important thing i believe you didnt test: the effect of 
mixing two descriptors on the _same_ selector: one %gs selector value 
loaded and used by glibc, and another %gs selector value loaded and used 
by the kernel, intermixed. It's the mixing that causes the descriptor 
cache reload. (unless i missed some detail about your testcase)

	Ingo
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