From: Andi Kleen <ak@suse.de>
To: Zachary Amsden <zach@vmware.com>
Subject: Re: [rfc patch] i386: don't save eflags on task switch
Date: Sun, 5 Nov 2006 18:01:18 +0100
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Cc: Linus Torvalds <torvalds@osdl.org>, Benjamin LaHaise <bcrl@kvack.org>,
       Chuck Ebbert <76306.1226@compuserve.com>,
       linux-kernel <linux-kernel@vger.kernel.org>
References: <200611040200_MC3-1-D04D-6EA3@compuserve.com> <200611050641.14724.ak@suse.de> <454D9A75.7010204@vmware.com>
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> 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.


-Andi
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