On Fri, Mar 15, 2024 at 01:07:22PM +0100, Christer Solskogen via misc wrote:
> On Fri, Mar 15, 2024 at 11:43 AM Zé Loff via misc <misc@openbsd.org> wrote:
>
> > Your cpu*.frequency lines show you that it does.
>
> In that case, what does hw.cpuspeed mean?
>
Jonathan Gray already told you that:
> > hw.cpuspeed is only updated when a set speed is selected by the kernel.
> > With turbo mode the hardware continually changes the speed without
> > notifying the kernel.
You have
cpu0: Enhanced SpeedStep 2693 MHz: speeds: 1701, 1700, 1600, 1500, 1400,
1300, 1200, 1100, 1000, 900, 800 MHz
on your dmesg, so you have a CPU that is meant to run at (up to)
1700MHz, but can go to 2700MHz in turbo mode.
The 1701Mhz speed ("normal max" + 1) is the speed that the kernel needs
to set to get it into turbo mode. So, when
hw.cpuspeed=1701
it means your CPU is running in turbo mode. If you or the kernel wants
to throttle it down to save power, hw.cpuspeed will change to something
lower.
As Jonathan said, when in turbo mode, the CPU it won't tell the kernel
about speed changes, but you can always get them from the
hw.sensors.cpu*.frequency readings. Which, incidentally, might not even
be the same for each CPU core, as they are throttled differently:
$ sysctl hw.sensors | grep frequency0
hw.sensors.cpu0.frequency0=2450000000.00 Hz
hw.sensors.cpu1.frequency0=2700000000.00 Hz
hw.sensors.cpu2.frequency0=2850000000.00 Hz
hw.sensors.cpu3.frequency0=2350000000.00 Hz
Hope this clears things up.
Cheers
Zé
P.S.: I'm by no means whatsoever an authority on this matter. I'm
replying because you asked me directly.
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