Re: [rfc patch] i386: don't save eflags on task switch

[Andi Kleen]

> For me, when compiled with -O2, it results in
> 
> 	84
> 	88
> 	132
> 
> which basically says: a "rdtsc->rdtsc" is 84 cycles, putting a "pushfl" in 
> between is another _4_ cycles, and putting a "popfl" in between is about 
> another 48 cycles. 

This means we should definitely change restore_flags() to only STI, 
never popf

-Andi
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