Intel TurboBoost in practice
mav at FreeBSD.org
Sat Jul 24 22:03:56 UTC 2010
Norikatsu Shigemura wrote:
> On Sat, 24 Jul 2010 16:53:10 +0300
> Alexander Motin <mav at freebsd.org> wrote:
>> PS: In this case benefit is small, but it is the least that can be
>> achieved, depending on CPU model. Some models allow frequency to be
>> risen by up to 6 steps (+798MHz).
> I tested on Core i7 640UM (Arrandale 1.2GHz -> 2.26GHz) with
> openssl speed (w/o aesni(4)) and
> /usr/src/tools/tools/crypto/cryptotest.c (w/ aesni(4)).
> http://people.freebsd.org/~nork/aesni/aes128cbc-noaesni.pdf 
> http://people.freebsd.org/~nork/aesni/aes128cbc-aesni.pdf 
> In my environment, according to aes128cbc-noaesni.pdf, at least,
> 30% performace up by Turbo Boost (I think).
The numbers are interesting, though they are not proving much, because
of many other factors may influence on result. It would be more
informative to do the tests with C1 and C2/C3 states used.
> And according to aes128cbc-aesni.pdf, at least, 100% performance
> up by Turbo Boost (I think).
This IMHO is even more questionable. Single, even boosted core shouldn't
be faster then 2, 3 and 4. I would say there is some scalability
problem. May be context switches, locking, or something else.
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