[Speed] Getting the project off the ground

Da_Blitz pypy at pocketnix.org
Wed Jul 6 21:11:24 CEST 2011


On Wed, Jul 06, 2011 at 09:01:20PM +0200, Antonio Cuni wrote:
> that would be really cool. However, I'm not sure it's enough to prevent
> "random noise".
> 
> E.g., I know that modern CPUs have a mechanism that turns off the unused cores
> in order to speed up the active ones (by slightly incrementing the frequency).
>  If this is the case, then I fear that the only way to have a precise
> benchmark is to run only one process at time.


Looks like a X5680 cpu so yes it has the turbo boost feature 
(http://en.wikipedia.org/wiki/Nehalem_(microarchitecture)#Server_.2F_Desktop_Processors_2) 
i am running an i7 for building pypy and have the same turbo boost 
feature and in practice have not found it to be an issue aslong as you 
are only running one translation at a time. as the workload is single 
threadded it ramps up nicely. a lock or two should prevent the turbo 
boost enabling/disabling erratic but it is also under kernel control. 

i havent investigated how much control the kernel has over it but i 
assume if you switch the cpu speed governers from performance over to 
user mode and manually set the freqency that should not be much of an 
issue

turbo mode is socket specific so the isolation i talked about in my 
last post would prevent compiles' from affecting the cpu freqency on 
the benchmark cpus

as a side note this may be a good time for my to push for making the 
benchmark scores user time + kernel time instead of wall clock time


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