Ubuntu's Power Consumption Tested
Ubuntu 7.10 "Gutsy Gibbon" is due out in just a few days and shipping with it is the Linux 2.6.22 kernel. One of the interesting additions to the Linux kernel since the 2.6.20-based Ubuntu 7.04 "Feisty Fawn" release has been the tickless kernel feature. If you hadn't read out tickless kernel article from earlier this year, the tickless kernel feature (CONFIG_NO_HZ) is designed to improve the power efficiency especially on servers and portable devices. This CONFIG_NO_HZ feature works by enabling on-demand timer interrupts that allow a system to idle for a longer period of time and avoiding useless interrupts. This is not only designed to reduce power consumption but to allow for the system to run cooler and an extended battery-life for mobile devices.
For this article we've decided to not only deliver power benchmarks from Ubuntu 7.10 and Ubuntu 7.04 to compare the tickless kernel effect, but we have went back and retested all of the Ubuntu releases going back to Ubuntu 5.04, or also known as Hoary Hedgehog. With the past six Ubuntu releases we had tested the power consumption of a Lenovo laptop when running from its AC charger and off the battery, when the system was idling and then again under load. We had also monitored the temperature of the Intel Centrino mobile processor. You may be surprised by the results of Ubuntu's power usage.
The laptop used to conduct all of these tests was a Lenovo ThinkPad R52. This ThinkPad R52 was equipped with an Intel Pentium M 750 (1.86GHz with Enhanced Intel SpeedStep Technology), 2GB of DDR2-533 system memory, ATI Radeon X300 64MB GPU, 15.4" 1400 x 1050 display, Intel 802.11g WiFi, and an 80GB IDE hard drive. Due to compatibility problems with the first Ubuntu release, Ubuntu 4.10 "Warty Warthog", we were unable to test its power consumption on the Lenovo R52. However, this laptop had no problems with Ubuntu 5.04 "Hoary Hedgehog", Ubuntu 5.10 "Breezy Badger", Ubuntu 6.06.1 LTS "Dapper Drake", Ubuntu 6.10 "Edgy Eft", Ubuntu 7.04 "Feisty Fawn", and the Ubuntu 7.10 "Gutsy Gibbon". While the final release of Ubuntu 7.10 isn't out yet, we had used a daily LiveCD build from early October.
When testing the Lenovo ThinkPad R52 with the power consumption from the AC adapter we had used a SeaSonic PowerAngel to monitor the Wattage. The battery discharge rate and CPU temperature were both obtained through the Linux IBM ACPI driver. During our idling tests, the notebook was simply running within the Ubuntu GNOME environment using the stock settings, but while the screensaver was not active. Both the idle and load results were recorded after 15 minutes when their power consumption had leveled off. The load tests consisted of running glxgears and CPU Burn-In to stress the CPU. We hadn't run Intel's PowerTOP due to issues with the older Ubuntu releases.
To recap the past Ubuntu releases, Ubuntu 5.04 had shipped with X.Org 6.8.2 and the Linux 2.6.10 kernel, Ubuntu 5.10 with Linux 2.6.12-9 and X.Org 6.8.2, Ubuntu 6.06.1 with X.Org 7.0.0 and Linux 2.6.15-26, Ubuntu 6.10 with X.Org 7.1.1 and the 2.6.17-10 kernel, Ubuntu 7.04 with the 2.6.20-15 kernel and X.Org 7.2.0, and Ubuntu 7.10 with the 2.6.22-12 kernel and X.Org 7.2 / X server 1.3.