Re: Laptop battery life on FreeBSD
- From: Shawn Badger <shawnbadger@xxxxxxxxx>
- Date: Tue, 27 Jan 2009 23:32:10 -0700
Bruce Cran wrote:
On Tue, 27 Jan 2009 16:19:31 -0700
Shawn Badger [1]<shawnbadger@xxxxxxxxx> 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@xxxxxxxxx
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- References:
- Laptop battery life on FreeBSD
- From: Shawn Badger
- Re: Laptop battery life on FreeBSD
- From: Bruce Cran
- Laptop battery life on FreeBSD
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