Messages in this thread | | | Date | Thu, 14 Aug 2008 14:09:43 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [RFC PATCH] x86 alternatives : fix LOCK_PREFIX race with preemptible kernel and CPU hotplug |
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* H. Peter Anvin (hpa@zytor.com) wrote: > Mathieu Desnoyers wrote: >> Sure, here are the updated tables. Basically, they show no significant >> difference between the NOP and the DS segment selector prefix >> approaches. > > Actually, unless I have blown my T-test completely, they show with a 80% > and 74% confidence (respective for the two benchmarks) that the DS case is > slightly *better* (0.26% and 0.20% better, respective), which makes it a > no-brainer. Doing around 10 runs of each is likely to confirm this > conclusion by pushing it into the 90+% interval. >
Yes, I think you are right.
> Note that since the difference is so small, and so can also be due to some > kind of systematic error (lower ambient temperature during the DS run > making the disk drive slightly faster, what have you.) >
I doubt it, because I made a "cache priming" run before the tests, which made sure the data was all populated in memory. But yeah, having different cpu clock calibration values/cpu clock frequency between reboots could also cause that kind of difference.
Mathieu
> -hpa
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