Re: [PLUG] CPU Scaling

[Walt Mankowski via plug <plug@lists.phillylinux.org>]

I've got a 2020 13" MacBook Pro. The processor is a 2.3 GHz Quad-Core Intel Core i7.

On Sun, Dec 12, 2021 at 09:57:31PM -0500, Aaron Mulder via plug wrote:
> I'm not sure which Mac you have, but the single-core max CPU speed might be
> quite a bit higher than you're quoting, so it may not be that the desktop
> is 50% faster in terms of clock speed, depending on the "threadedness" of
> your code.  For instance, the MacBook Pro 13-Inch Core i7 2.3 GHz from 2020
> has an i7-1068NG7 CPU which indeed has a base frequency of 2.3 GHz but goes
> up to 4.1 GHz single-core:
> 
> https://everymac.com/systems/apple/macbook_pro/specs/macbook-pro-core-i7-2.3-quad-core-13-2020-4-thunderbolt-3-ports-scissor-specs.html
> https://ark.intel.com/content/www/us/en/ark/products/196593/intel-core-i71068ng7-processor-8m-cache-up-to-4-10-ghz.html
> 
> Thanks,
>        Aaron
> 
> On Sun, Dec 12, 2021 at 5:42 PM Walt Mankowski via plug <
> plug@lists.phillylinux.org> wrote:
> 
> > Hi,
> >
> > As usual in December I've been working my way through the awesome Advent
> > of Code <https://adventofcode.com/>problems. (This year we're saving
> > Christmas by riding around in a submarine. Don't ask.)
> >
> > While working on today's problem <https://adventofcode.com/2021/day/12> I
> > noticed that my code ran about twice as fast on my Apple laptop than my
> > Ubuntu desktop, despite the fact that my desktop's CPUs are over 50% faster
> > (3.5 GHz AMD vs 2.3 GHz Intel Core i7). When I looked in /proc/cpuinfo I
> > saw that the "cpu MHz" field was only 1400!
> >
> > I did some searches online and discovered this seems to be due to
> > something called "CPU Scaling". I've looked at /proc/cpuinfo subsequently
> > and I've also run cpufreq-info(1) and the numbers vary quite a bit. I'm
> > guessing the system is dynamically adjusting the CPU speed based on the
> > current system load.
> >
> > I've never noticed this before so I don't know if it's been in effect for
> > a while, or if it's something new in Ubuntu 21.10. I'm not sure yet if I
> > want to keep it or turn it off, but I would like to know more about where
> > it's set and how to tune it. Unfortunately most of the information I've
> > been able to find out about it seems fairly dated and predates Ubuntu's
> > adoption of systemd. Can anyone point me to more up to date information?
> >
> > Thanks.
> >
> > Walt
> >
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