Date: Sun, 24 May 2015 01:57:01 +1000 (EST) From: Ian Smith <smithi@nimnet.asn.au> To: Kimmo Paasiala <kpaasial@gmail.com> Cc: "freebsd-stable@freebsd.org" <freebsd-stable@freebsd.org> Subject: Re: CPU frequency doesn't drop below 1200MHz (like it used to) Message-ID: <20150524010831.W7173@sola.nimnet.asn.au> In-Reply-To: <CA%2B7WWSeziTc5viAbDpkqj85B%2BHFdea0WwOf6Q%2BCuRQ4EGAKp2A@mail.gmail.com> References: <555C71C8.4080007@gmx.com> <555EDBBB.4090107@gmx.com> <20150522104213.4e083225@nonamehost.local> <CA%2B7WWSfnsKn1Z3n1KS39iFZ%2B22ZzLsCke7mtnP%2BSAZh6M_cxCg@mail.gmail.com> <20150523014640.K7173@sola.nimnet.asn.au> <CA%2B7WWSfdC=P689XJeGjKCH49k4EVR7X5XR23_UeqGKy7mabVkw@mail.gmail.com> <20150523163014.U7173@sola.nimnet.asn.au> <CA%2B7WWSf8q-Amwy60NSfC=_ZcguiTQN9qCmx9ArP4x9_zgTqq7A@mail.gmail.com> <20150523234646.R7173@sola.nimnet.asn.au> <CA%2B7WWSeziTc5viAbDpkqj85B%2BHFdea0WwOf6Q%2BCuRQ4EGAKp2A@mail.gmail.com>
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On Sat, 23 May 2015 17:40:26 +0300, Kimmo Paasiala wrote: > On Sat, May 23, 2015 at 5:15 PM, Ian Smith <smithi@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@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
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