Date: Tue, 12 May 2009 00:21:22 +0400 From: Dmitry Kolosov <ivakras1@gmail.com> To: freebsd-acpi@freebsd.org Subject: Re: Fighting for the power. Message-ID: <200905120021.23223.ivakras1@gmail.com> In-Reply-To: <20090511191309.79F0E1CC0B@ptavv.es.net> References: <20090511191309.79F0E1CC0B@ptavv.es.net>
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=F0=CF=CE=C5=C4=C5=CC=D8=CE=C9=CB 11 =CD=C1=D1 2009 23:13:09 Kevin Oberman = =D0=C9=D3=C1=CC=C9: > > From: Dmitry Kolosov <ivakras1@gmail.com> > > Date: Mon, 11 May 2009 22:59:13 +0400 > > Sender: owner-freebsd-acpi@freebsd.org > >=20 > > =F0=CF=CE=C5=C4=C5=CC=D8=CE=C9=CB 04 =CD=C1=D1 2009 02:18:14 Alexander = Motin =D0=C9=D3=C1=CC=C9: > > > I would like to summarize some of my knowledge on reducing FreeBSD po= wer > > > consumption and describe some new things I have recently implemented = in > > > 8-CURRENT. The main character of this story is my 12" Acer TravelMate > > > 6292 laptop with C2D T7700 2.4GHz CPU, 965GM chipset and SATA HDD, un= der > > > amd64 8-CURRENT. > > >=20 > > > Modern systems, especially laptops, are implementing big number of=20 > > > power-saving technologies. Some of them are working automatically, ot= her=20 > > > have significant requirements and need special system tuning or=20 > > > trade-offs to be effectively used. > > >=20 > > > So here is the steps: > > >=20 > > > 1. CPU > > > CPU is the most consuming part of the system. Under the full load it > > > alone may consume more then 40W of power, but for real laptop usage t= he > > > most important is idle consumption. > > > Core2Duo T7700 CPU has 2 cores, runs on 2.4GHz frequency, supports EI= ST > > > technology with P-states at 2400, 2000, 1600, 1200 and 800MHz levels, > > > supports C1, C2 and C3 idle C-states, plus throttling. So how can we = use it: > > > P-states and throttling > > > Enabling powerd allows to effectively control CPU frequency/voltage > > > depending on CPU load. powerd on recent system can handle it quite > > > transparently. By default, frequency controlled via mix of EIST and > > > throttling technologies. First one controls both core frequency and > > > voltage, second - only core frequency. Both technologies give positive > > > power-saving effect. But effect of throttling is small and can be > > > completely hidden by using C2 state, that's why I recommend to disable > > > throttling control by adding to /boot/loader.conf: > > > hint.p4tcc.0.disabled=3D1 > > > hint.acpi_throttle.0.disabled=3D1 > > > In my case frequency/voltage control saves about 5W of idle power. > > > C-states > > > - C1 stops clock on some parts of CPU core during inactivity. It is > > > safe, cheap and supported by CPUs for ages. System uses C1 state by d= efault. > > > - C2 state allows CPU to turn off all core clocks on idle. It is al= so > > > cheap, but requires correct ACPI-chipset-CPU interoperation to be use= d. > > > Use of C2 state can be enabled by adding to /etc/rc.conf: > > > performance_cx_lowest=3D"C2" > > > economy_cx_lowest=3D"C2" > > > Effect from this state is not so big when powerd is used, but still > > > noticeable, > > > - C3 state allows CPU completely stop all internal clocks, reduce > > > voltage and disconnect from system bus. This state gives additional > > > power saving effect, but it is not cheap and require trade-offs. > > > As soon as CPU is completely stopped in C3 state, local APIC timers in > > > each CPU core, used by FreeBSD as event sources on SMP, are not > > > functioning. It stops system time, breaks scheduling that makes system > > > close to dead. The only solution for this problem is to use some > > > external timers. Originally, before SMP era, FreeBSD used i8254 (for = HZ) > > > and RTC (for stats) chipset timers. I have made changes to 8-CURRENT = to > > > resurrect them for SMP systems. To use them, you can disable local AP= IC > > > timers by adding to /boot/loader.conf: > > > hint.apic.0.clock=3D0 > > > Also, to drop/rise voltage on C3, CPU needs time (57us for my system). > > > It means that C3 state can't be effectively used when system is waking > > > up often. To increase inactivity periods we should reduce interrupt r= ate > > > as much as possible by adding to loader.conf: > > > kern.hz=3D100 > > > It may increase system response time a bit, but it is not significant > > > for laptop. Also we may avoid additional 128 interrupts per second per > > > core, by the cost of scheduling precision, with using i8254 timer also > > > for statistic collection purposes instead of RTC clock, by using anot= her > > > newly added option: > > > hint.atrtc.0.clock=3D0 > > > As result, system has only 100 interrupts per core and CPUs are using= C3 > > > with high efficiency: > > > %sysctl dev.cpu |grep cx > > > dev.cpu.0.cx_supported: C1/1 C2/1 C3/57 > > > dev.cpu.0.cx_lowest: C3 > > > dev.cpu.0.cx_usage: 0.00% 0.00% 100.00% last 7150us > > > dev.cpu.1.cx_supported: C1/1 C2/1 C3/57 > > > dev.cpu.1.cx_lowest: C3 > > > dev.cpu.1.cx_usage: 0.00% 0.00% 100.00% last 2235us > > > Result of effective C3 state usage, comparing to C2+powerd, is about = 2W. > > >=20 > > > 2. PCI devices > > > PCI bus provides method to control device power. For example, I have > > > completely no use for my FireWire controller and most of time - EHCI = USB > > > controller. Disabling them allows me to save about 3W of power. To > > > disable all unneeded PCI devices you should build kernel without their > > > drivers and add to loader.conf: > > > hw.pci.do_power_nodriver=3D3 > > > To enable devices back all you need to do is just load their drivers = as > > > modules. > > >=20 > > > 3. Radios > > > WiFi and Bluetooth adapters can consume significant power when used (= up > > > to 2W when my iwn WiFi is connected) or just enabled (0.5W). Disabling > > > them with mechanical switch on laptop case saves energy even when they > > > are not connected. > > >=20 > > > 4. HDA modem > > > I was surprised, but integrated HDA modem consumed about 1W of power > > > even when not used. I have used the most radical solution - removed it > > > mechanically from socket. Case surface in that area become much coole= r. > > >=20 > > > 5. HDA sound > > > To reduce number of sound generated interrupts I have added to the > > > loader.conf: > > > hint.pcm.0.buffersize=3D65536 > > > hint.pcm.1.buffersize=3D65536 > > > hw.snd.feeder_buffersize=3D65536 > > > hw.snd.latency=3D7 > > >=20 > > > 6. HDD > > > First common recommendation is use tmpfs for temporary files. RAM is > > > cheap, fast and anyway with you. > > > Also you may try to setup automatic idle drive spin-down, but if it is > > > the only system drive you should be careful, as every spin-up reduces > > > drive's life time. > > > For several months (until I have bought SATA SSD) I have successfully > > > used SDHC card in built-in PCI sdhci card reader as main filesystem. = On > > > random read requests it is much faster then HDD, but it is very slow = on > > > random write. Same time it consumes almost nothing. USB drives could > > > also be used, but effect is much less as EHCI USB controller consumes > > > much power. > > > Spinning-down my 2.5" Hitachi SATA HDD saves about 1W of power. Remov= ing > > > it completely saves 2W. > > >=20 > > > 7. SATA > > > Comparing to PATA, SATA interface uses differential signaling for data > > > transfer. To work properly it has to transmit pseudo-random scrambled > > > sequence even when idle. As you understand, that requires power. But > > > SATA implements two power saving modes: PARTIAL and SLUMBER. These mo= des > > > could be activated by either host or device if both sides support the= m. > > > PARTIAL mode just stops scrambling, but keeps neutral link state, res= ume > > > time is 50-100us. SLUMBER mode powers down interface completely, but > > > respective resume time is 3-10ms. > > > I have added minimal SATA power management to AHCI driver. There are > > > hint.ata.X.pm_level loader tunables can be used to control it now. > > > Setting it to 1 allows drive itself to initiate power saving, when it > > > wish. Values 2 and 3 make AHCI controller to initiate PARTIAL and > > > SLUMBER transitions after every command completion. > > > Note that SATA power saving is not compatible with drive hot-swap, as > > > controller unable to detect drive presence when link is powered-down. > > > In my case PARTIAL mode saves 0.5W and SLUMBER - 0.8W of power. > > >=20 > > > So what have I got? To monitor real system power consumption I am usi= ng > > > information provided by ACPI battery via `acpiconf -i0` command: > > >=20 > > > Original system: > > > Design capacity: 4800 mAh > > > Last full capacity: 4190 mAh > > > Technology: secondary (rechargeable) > > > Design voltage: 11100 mV > > > Capacity (warn): 300 mAh > > > Capacity (low): 167 mAh > > > Low/warn granularity: 32 mAh > > > Warn/full granularity: 32 mAh > > > Model number: Victoria > > > Serial number: 292 > > > Type: LION > > > OEM info: SIMPLO > > > State: discharging > > > Remaining capacity: 93% > > > Remaining time: 2:24 > > > Present rate: 1621 mA > > > Voltage: 12033 mV > > >=20 > > > Tuned system: > > > %acpiconf -i0 > > > Design capacity: 4800 mAh > > > Last full capacity: 4190 mAh > > > Technology: secondary (rechargeable) > > > Design voltage: 11100 mV > > > Capacity (warn): 300 mAh > > > Capacity (low): 167 mAh > > > Low/warn granularity: 32 mAh > > > Warn/full granularity: 32 mAh > > > Model number: Victoria > > > Serial number: 292 > > > Type: LION > > > OEM info: SIMPLO > > > State: discharging > > > Remaining capacity: 94% > > > Remaining time: 4:47 > > > Present rate: 826 mA > > > Voltage: 12231 mV > > >=20 > > > So I have really doubled my on-battery time by this tuning - 4:47 hou= rs=20 > > > instead of 2:24 with default settings. Preinstalled vendor-tuned Wind= ows=20 > > > XP on the same system, provides maximum 3:20 hours. > > >=20 > >=20 > > My EC does not present rate and time info: > > 10:49pm][/home/onyx# acpiconf -i0 > > Design capacity: 6000 mAh > > Last full capacity: 3328 mAh > > Technology: secondary (rechargeable) > > Design voltage: 14800 mV > > Capacity (warn): 172 mAh > > Capacity (low): 104 mAh > > Low/warn granularity: 10 mAh > > Warn/full granularity: 25 mAh > > Model number: Primary > > Serial number: =20 > > Type: LION > > OEM info: Hewlett-Packard > > State: high=20 > > Remaining capacity: 100% > > Remaining time: unknown > > Present rate: unknown > > Voltage: 12522 mV > >=20 > > Where to dig? I'm realy need at least 'present rate' to fight for the > > power.. Also it is an error in capacity detection, i think. Any ideas? >=20 > Is the system connected to AC power when you issue the command? Many > systems do not provide this information unless they are no battery > power. Thy may also need to have been on battery for at least a minute > or two to calculate drain rate. (Also, that battery is getting fairly > old. It has only 55% of it's designed capacity.) 20 minutes on battery. Still no 'Remaining time' nor 'Present rate'. It dra= ins 1% in a minute, while economy profile is C3 state for processor and 500= MHz of speed. Anyway, laptop runs less than a hour on battery on economy pr= ofile. That laptop (HP Pavilion dv6840er) is less than 1 year old. It's C4 state available in BIOS settings, i'll try it.
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