The Linux Kernel Power Problems On Older Desktop Hardware

As mentioned last week, a plethora of Linux power tests are on the way now that we have found an AC power meter with USB interface that works under Linux and we've been able to integrate nicely into the Phoronix Test Suite and its sensor monitoring framework. In this article is one of the first tests that have been completed using this power-measuring device as we monitored the Linux kernel power consumption for an old Intel Pentium 4 and ATI Radeon 9200 system for the past several kernel releases. Even this very old desktop system looks to be affected by the kernel power problems.

This testing was done both out of curiosity and in my quest of tracking down the major Linux kernel power regressions. All the kernel power regression hunting up to this point had been done using battery-backed mobile platforms, but now it's time to turn to desktops / workstations to see if there's outstanding problems there too. Based upon being out of my office for the early part of this week, the desktop power testing began on one system that I had access to: a very old Socket 478 system.

Besides seeing if the kernel power regressions affect this hardware too, these results should be interesting and useful for narrowing down the problems since the Linux support has been mature for this hardware for a number of years. The hardware is also different from modern processors and graphics cards. The Intel Pentium 4 "C" 2.8GHz processor does not have Enhanced Intel SpeedStep Technology (EIST) like modern CPUs and the ATI Radeon 9200 PRO (R200) graphics card does not have PowerPlay or much else in the way of power management.

With the 2.8GHz Intel Pentium 4 and ATI Radeon 9200 PRO AGP graphics card, also making up this system was an Abit SG72 motherboard with SiS 661FX-964L chipset, 512MB of DDR system memory, and a 80GB Western Digital IDE hard drive. Ubuntu 11.04 was installed to the system with the GNOME 2.32.1 desktop, X.Org Server 1.10.1, xf86-video-ati 6.14.0, Mesa 7.10.2, GCC 4.5.2, and an EXT4 file-system. Each major kernel release was tested from the latest Linux 3.0 daily snapshot to the Linux 2.6.32 long-term support series. All the "vanilla" kernel releases were obtained from the Ubuntu mainline kernel package repository.

With each kernel release, we measured the power consumption of the system using the Watts Up Pro device that was being automatically polled by the Phoronix Test Suite. The power was measured while running the battery-power-usage test profile along with the 7-Zip Compression, Apache, x264, OpenArena and World of Padman workloads. While not the focus of this testing, the actual results from the each of these test profiles are also included.