The Changelog - Environment & Energy

Bicycling to Work

nospam@example.com (John Goerzen) — Fri, 23 May 2008 18:59:49 -0500

We hear a lot these days about the price of gas, energy efficiency, and the like. But, in the United States, outside of a few progressive cities, there aren't a lot of people that are using the ultimate zero-emissions transportation technology: bicycles.

That's really too bad, because bicycles are a lot cheaper to operate than cars even before you consider gas prices. They also are great exercise and are probably faster, safer, and more convenient than you think.

I live about 10 miles (16 km) from work, which includes several miles on sand roads. I haven't bicycled in about 6 years. Last week, I got my bicycle out, touched it up a bit, and started riding. Sunday I rode in to work and back as a test. As soon as I get a bit of gear (hopefully by the middle of next week), I plan to start riding bike to work at least 3 days a week.

I've picked up some tips along the way. Let's talk about a few of them.

Safety

Many people think bicycling is dangerous. In fact, bicycling is about as safe as driving an SUV. Not only that, but only 10% of bicycling accidents occur when you are hit from behind (and 90% of those produce only minor injuries). It turns out that the vast majority of bicycling accidents occur because people are not riding on the road with traffic, or are acting unpredictably. Following some basic safety advice can make you safer in a bicycle than an SUV. Oh, and don't drink and ride; 24% of fatal bicycle accidents involve an intoxicated rider.

Distance

Think it's too far? Think again. It's fairly easy for an untrained, unfit person to ride a bicycle up to 10 miles without working hard at it. That can probably be done in about an hour. As you get more fit and used to the bike, you may be able to go that distance in half that time. Also, get pannier bags for your bicycle. They attach in back and let you carry work clothes, laptops, etc. without having to use a backpack.

Smell

Many people with office jobs are concerned about this. Not everywhere has a convenient shower. Check out these tips from the Tips and Tricks for Biking to Work manual.

I'm excited about it, and will be sure to post more here on how it goes.

Saving Power with CPU Frequency Scaling

nospam@example.com (John Goerzen) — Thu, 07 Dec 2006 05:43:00 -0600

Yesterday I wrote about the climate crisis. Today, let's start doing something about it.

Electricity, especially in the United States and China, turns out to be a pretty dirty energy source. Most of our electricity is generated using coal, which despite promises of "clean coal" to come, burns dirty. Not only does it contribute to global warming, but it also has been shown to have an adverse impact on health.

So let's start simple: reduce the amount of electricity our computers consume. Even for an individual person, this can add up to quite a bit of energy (and money) savings in a year. When you think about multiplying this over companies, server rooms, etc., it adds up fast. This works on desktops, servers, laptops, whatever.

The easiest way to save power is with CPU frequency scaling. This is a technology that lets you adjust how fast a running CPU runs, while it's running. When CPUs run at slower speeds, they consume less power. Most CPUs are set to their maximum speed all the time, even when the system isn't using them. Linux has support for keeping the CPU at maximum speed unless it is idle. By turning on this feature, we can save power at virtually no cost to performance. The Linux feature to handle CPU frequency scaling is called cpufreq.

Set up modules

Let's start by checking to see whether cpufreq support is already enabled in your kernel. These commands will need to be run as root.

# cd /sys/devices/system/cpu/cpu0
# ls -l

If you see an entry called cpufreq, you are good and can skip to the governor selection below.

If not, you'll need to load cpufreq support into your kernel. Let's get a list of available drivers:

# ls /lib/modules/`uname -r`/kernel/arch/*/kernel/cpu/cpufreq

Now it's guess time. It doesn't really hurt if you guess wrong; you'll just get a harmless error message. One hint, though: try acpi-cpufreq last; it's the option of last resort.

On my system, I see:

acpi-cpufreq.ko     longrun.ko      powernow-k8.ko         speedstep-smi.ko
cpufreq-nforce2.ko  p4-clockmod.ko  speedstep-centrino.ko
gx-suspmod.ko       powernow-k6.ko  speedstep-ich.ko
longhaul.ko         powernow-k7.ko  speedstep-lib.ko

For each guess, you'll run modprobe with the driver name. I have an Athlon64, which is a K8 machine, so I run:

#modprobe powernow-k8

Note that you leave off the ".ko" bit. If you don't get any error message, it worked.

Once you find a working module, edit /etc/modules and add the module name there (again without the ".ko") so it will be loaded for you on boot.

Governor Selection

Next, we need to load the driver that tells the kernel what governor to use. The governor is the thing that monitors the system and adjusts the speed accordingly.

I'm going to suggest the ondemand governor. This governor keeps the system's speed at maximum unless it is pretty sure that the system is idle. So this will be the one that will let you save power with the least performance impact.

Let's load the module now:

# modprobe cpufreq_ondemand

You should also edit /etc/modules and add a line that says simply cpufreq_ondemand to the end of the file so that the ondemand governor loads at next boot.

Turning It On

Now, back under /sys/devices/system/cpu/cpu0, you should see a cpufreq directory. cd into it.

To turn on the ondemand governor, run this:

# echo echo ondemand > scaling_governor

That's it, your governor is enabled. You can see what it's doing like this:

# cat cpuinfo_min_freq
800000
# cat cpuinfo_max_freq
2200000
# cat cpuinfo_cur_freq
800000

That shows that my CPU can go as low as 800MHz, as high as 2.2GHz, and that at the present moment, it's running at 800MHz presently.

Now, check your scaling governor settings:

# cat scaling_min_freq
800000
# cat scaling_max_freq
800000

This is showing that the system is constraining the governor to only ever operate on an 800MHz to 800MHz range. That's not what I want; I want it to scale over the entire range of the CPU. Since my cpuinfo_max_freq was 2200000, I want to write that out to scaling_max_freq as well:

echo 2200000 > scaling_max_freq

Making This The Default

The last step is to make this happen on each boot. Open up your /etc/sysfs.conf file. If you don't have one, you will want to run a command such as apt-get install sysfsutils (or the appropriate one for your distribution).

Add a line like this:

devices/system/cpu/cpu0/cpufreq/scaling_governor = ondemand
devices/system/cpu/cpu0/cpufreq/scaling_max_freq = 2200000

Remember to replace the 2200000 with your own cpu_max_freq value.

IMPORTANT NOTE: If you have a dual-core CPU, or more than one CPU, you'll need to add a line for each CPU. For instance:

devices/system/cpu/cpu1/cpufreq/scaling_governor = ondemand
devices/system/cpu/cpu1/cpufreq/scaling_max_freq = 2200000

You can see what all CPU devices you have with ls /sys/devices/system/cpu.

Now, save this file, and you'll have CPU frequency scaling saving you money, and helping the environment, every time you boot. And with the ondemand governor, chances are you'll never notice any performance loss.

This article showed you how to save power using CPU frequency scaling on Linux. I have no idea if it's possible to do the same on Windows, Mac, or the various BSDs, but it would be great if someone would leave comments with links to resources for doing that if so.

Updated: added scaling_max_freq info

The Climate Crisis

nospam@example.com (John Goerzen) — Wed, 06 Dec 2006 20:48:40 -0600

Wow.

We just watched An Inconvenient Truth. Not much in there was new to me, but to see it all presented at once is amazing.

There are vast undisputed scientific facts out there -- for instance, that CO2 content in the atmosphere is higher than it's been ever -- and we can go back 650,000 years. The linkage between that and temperatures is inescapable.

Gore makes a good point: shouldn't we be worried about more than terrorism?

Does the thought of parts of Manhattan, San Francisco, and large parts of Florida going underwater suggest a problem exists?

This really is critical and urgent.

We've already been thinking about it lately as we renovate our house. We're paying a little more now for things like airtight insulation, low-energy lighting, efficient heating. Not only will it save us money in the long run, it will help improve our lives and Jacob's life down the road.

The movie's website is over at climatecrisis.net.