Messages in this thread | | | Date | Thu, 31 Jan 2002 12:33:09 +0100 (CET) | From | Ingo Molnar <> | Subject | Re: [patch] [sched] x86 idle thread should clear %fs, %gs |
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On Tue, 29 Jan 2002, Pavel Machek wrote:
> > so it appears that this lowlevel x86 performance bug(?) is more than 11 > > years old! :-) > > Probably 386's were not optimized for %fs==%gs==0 case? > > BTW does it really make a difference for the CPU?
whether %fs/%gs is 0 or not? With the current 2.5.3-pre6 task switching code there definitely is a performance difference, because we optimize the 'both values are 0' case. With the original TSS-based task switching microcode i suspect it made a difference as well. (switching between two different %fs/%gs values should be slower.)
Ingo
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