freebsd stable - May 2015 - CPU frequency doesn't drop below 1200MHz (like it used to)

On Sat, May 23, 2015 at 6:57 PM, Ian Smith <smithi at nimnet.asn.au>
wrote:
> On Sat, 23 May 2015 17:40:26 +0300, Kimmo Paasiala wrote:
>  > On Sat, May 23, 2015 at 5:15 PM, Ian Smith <smithi at
nimnet.asn.au> wrote:
> [..]
>  > >  > It's an Intel Atom running amd64 version of FreeBSD
stable/10:
>  > >  >
>  > >  > FreeBSD firewall.rdnzl.info 10.1-STABLE FreeBSD
10.1-STABLE #1
>  > >  > r283292: Sat May 23 01:08:03 EEST 2015
>  > >  > root at firewall.rdnzl.info:/usr/obj/usr/src/sys/GENERIC 
amd64
>  > >  >
>  > >  > CPU: Intel(R) Atom(TM) CPU D510   @ 1.66GHz (1666.68-MHz
K8-class CPU)
>  > >  >   Origin="GenuineIntel"  Id=0x106ca  Family=0x6 
Model=0x1c  Stepping=10
>  > >  >  
Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
>  > >  >  
Features2=0x40e31d<SSE3,DTES64,MON,DS_CPL,TM2,SSSE3,CX16,xTPR,PDCM,MOVBE>
>  > >  >   AMD Features=0x20100800<SYSCALL,NX,LM>
>  > >  >   AMD Features2=0x1<LAHF>
>  > >  >   TSC: P-state invariant, performance statistics
>  > >  >
>  > >  > Powerd was working on 10.1-RELEASE but stopped working
after upgrade
>  > >  > to 10-STABLE and nothing was changed in BIOS settings.
> [..]
>  > >  > However, reading the other replies to this thread I get
the impression
>  > >  > that powerd(8) doesn't actually save energy on this
platform and I'm
>  > >  > better off without it?
>  > >
>  > > No, I don't think that's correct; using deeper C-states
is most likely a
>  > > bigger win, but higher than needed CPU freq will still use extra
power,
>  > > so run hotter. `sysctl dev.cpu` will also reveal your C-state
usage.
>  > >
>  > > Reason I'm pursuing this is that this change shouldn't
hurt, but it will
>  > > flush out those cases where people were only getting cpufreq due
to use
>  > > of a 'relative' cpufreq driver like p4tcc, unless
EST's enabled in BIOS;
>  > > I suspect yours may be one such case :)  If not, there's a
bug to fix.
>
> Seems _I've_ got a bug to fix; I need to stop assuming all modern Intel
> CPUs are going to make SpeedStep and/or deeper C-states available :(
>
>  > Looking deeper into this it appears I don't have speedstep (EST)
>  > support in the CPU it being a crappy Atom D510:
>  >
>  > http://ark.intel.com/products/43098
>
> Indeed.  It is rated at only 13W TDP, so relatively low power anyway.
>
>  > This the full 'sysctl dev.cpu' output:
>  >
>  > % sysctl dev.cpu
>
>  > dev.cpu.3.cx_usage: 100.00% last 65712us
>  > dev.cpu.3.cx_lowest: C1
>  > dev.cpu.3.cx_supported: C1/1/0
> [..]
>  > dev.cpu.0.cx_usage: 100.00% last 3132us
>  > dev.cpu.0.cx_lowest: C1
>  > dev.cpu.0.cx_supported: C1/1/0
>  > dev.cpu.0.%parent: acpi0
>  > dev.cpu.0.%pnpinfo: _HID=none _UID=0
>  > dev.cpu.0.%location: handle=\_PR_.P001
>  > dev.cpu.0.%driver: cpu
>  > dev.cpu.0.%desc: ACPI CPU
>  > dev.cpu.%parent:
>
> It doesn't even provide dev.cpu.0.freq, and has no deeper C-states
> ('Idle States' on that page) available, so it looks like you may as
well
> not bother running powerd.  Others maybe can offer better suggestions.
>
>  > So I should keep those two hints in loader.conf to use p4tcc I guess?
>
> If this is a desktop I'd just let it run flat out, ie disable p4tcc and
> acpi_throttle, have no cpufreq and forget powerd.
>
> If it's a laptop and power consumption on battery matters to you, you
> could see if p4tcc's lower frequencies actually save any power much, by
> running 'powerd -v' in a terminal while testing with different
loads, or
> if your 'acpiconf -i0' shows discharging rates in mA or mW, or
both.
>
> Sorry again for my poor assumption, and thanks for the data point!
>
> cheers, Ian
It's a firewall/router with some minimal services like nginx running.
I'll just leave it like it's now without any frequency control.

Thanks,

-Kimmo

Frequency control may not be relevant on that platform.

Try installing the intel-pcm package; then

# kldload cpuctl
# pcm.x 1

Then paste some of that in here. Let's see if the CPU is idling some other
way.



-adrian