Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [PATCH] i386-pda UP optimization | Date | Wed, 15 Nov 2006 18:24:35 +0100 |
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On Wednesday 15 November 2006 18:20, Ingo Molnar wrote: > > * Andi Kleen <ak@suse.de> wrote: > > > On Wednesday 15 November 2006 12:27, Eric Dumazet wrote: > > > Seeing %gs prefixes used now by i386 port, I recalled seeing strange > > > oprofile results on Opteron machines. > > > > > > I really think %gs prefixes can be expensive in some (most ?) cases, > > > even if the Intel/AMD docs say they are free. > > > > They aren't free, just very cheap. > > Eric's test shows a 5% slowdown. That's far from cheap.
I have my doubts about the accuracy of his test results. That is why I asked him to double check.
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