Date: Tue, 27 Jan 2009 23:32:10 -0700 From: Shawn Badger <shawnbadger@gmail.com> To: Bruce Cran <bruce@cran.org.uk> Cc: freebsd-questions@freebsd.org Subject: Re: Laptop battery life on FreeBSD Message-ID: <497FFBEA.1040102@gmail.com> In-Reply-To: <20090128060956.0c164685@gluon> References: <497F9683.3080905@gmail.com> <20090128060956.0c164685@gluon>
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Bruce Cran wrote: On Tue, 27 Jan 2009 16:19:31 -0700 Shawn Badger [1]<shawnbadger@gmail.com> wrote: Hi, I recently installed FreeBSD 7.1 on my laptop, replacing Arch Linux and I noticed a significant drop in my battery life (from ~3 hours to ~1.5 hours). I realize that Linux has their "tickless" kernel, which I am sure explains the difference, but my question is... is there anything I can do in FreeBSD right now to improve this? And is there going to be any work done the kernel to allow the hardware to enter into a low-power state for an extended period of time? My laptop is an Acer Travelmate 4100 which has the following hardware: - Pentium M 1.6 GHz processer - 2 GB RAM - integrated video/sound - 802.11bg / bluetooth I'm somewhat of a minimalist and don't use X11. I've disabled the bluetooth adapter, but frequently use my wireless adapter (intel pro/2200bg). Does anyone have any suggestions that could potentially extend my battery life? powerd isn't run by default, so the laptop will always be running at maximum frequency. By putting powerd_enable="YES" in /etc/rc.conf the CPU will throttle back whenever the system is idle. You can also tell FreeBSD to enter lower Cx states when idle by setting dev.cpu.x.cx_lowest, if it's supported. For example my VIA EPIA system has the following dev.cpu tree: sysctl dev.cpu dev.cpu.0.%desc: ACPI CPU dev.cpu.0.%driver: cpu dev.cpu.0.%location: handle=\_PR_.CPU0 dev.cpu.0.%pnpinfo: _HID=none _UID=0 dev.cpu.0.%parent: acpi0 dev.cpu.0.freq: 533 dev.cpu.0.freq_levels: 533/-1 266/-1 dev.cpu.0.cx_supported: C1/0 C2/90 C3/900 dev.cpu.0.cx_lowest: C1 dev.cpu.0.cx_usage: 100.00% 0.00% 0.00% My processor now throttles down to 100 MHz when idle and my fan no longer blows like crazy - this is exactly what I was hoping for. Thanks, Shawn References 1. mailto:shawnbadger@gmail.com
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