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Date:	Sun, 5 Nov 2006 18:01:18 +0100
From:	Andi Kleen <>
To:	Zachary Amsden <>
Cc:	Linus Torvalds <>,
	Benjamin LaHaise <>,
	Chuck Ebbert <>,
	linux-kernel <>
Subject: Re: [rfc patch] i386: don't save eflags on task switch

> sti is expensive as well; iirc just as expensive on most processors as 
> popf, 

On K8 STI is 4 cycles.

> although I don't have hard numbers to back this up on hand.  An  
> _unlikely_ jcc + popf? is better than a sti, for sure, but a likely 
> jcc+popf could cost more than a jcc+sti, depending on model.

99.9999% of all restore_flags just need STI.

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