Nailing the Cause of Recent Linux Power Issues

An anonymous reader writes "For the Linux kernel power regressions that were found a few months ago, and hit in Ubuntu 11.04, Phoronix has found the regression that's still present in the Linux 3.0 kernel. The power regression is caused by a change in ASPM, the Active-State Power Management, for PCI Express support."

Comments

Summary: not a Linux problem, but a BIOS problem

[ArsenneLupin]

To sum up the article in 3 sentences:

It's due to some buggy BIOSes not properly advertising power-saving features of PCIE cards. Older kernels didn't honor those BIOS hints, and disabled power to unused PCIE cards anyways (causing hangs in rare cases), whereas new kernels do the right thing (causing power wastage in lots of cases). The workaround is to specify pcie_aspm=force on the boot (Grub) command line, to tell the kernel to forge ahead, and just use power management on these cards regardless of the BIOS advice.

Re:No more Moronix, please!

[qinjuehang]

As bad as some of the Phoronix articles can be, they have contributed a lot to the community. After all, they played a pivotal role in setting up openbenchmarking.org, and are pretty much the only source of Linux hardware reviews.

Re:"serious bug" my ass

[David Gerard]

You are entirely correct. See Matthew Garrett's blog for the icky details of EFI on Linux. He makes this hideous piece of shit work for a living.