1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

The Linux 3.0 Kernel Will... Reboot Better?

Linux Kernel

Published on 31 May 2011 06:47 PM EDT
Written by Michael Larabel in Linux Kernel
12 Comments

Beyond file-system cleancache support, a Microsoft Kinect driver, Intel Ivy Bridge support, and various open-source graphics driver improvements, the Linux 3.0 kernel may also reboot your system better. Yes, really.

Matthew Garrett of Red Hat today is blogging about the different ways to reset an x86 system and the limitations of these five different methods available on Linux. These methods include using kbd (rebooting via the keyboard controller), triple (generating a triple fault), PCI, EFI, and ACPI.

Matthew recently began exploring how Microsoft Windows handles the reboot process. "A while back I did some tests with Windows running on top of qemu. This is a great way to evaluate OS behaviour, because you've got complete control of what's handed to the OS and what the OS tries to do to the hardware. And what I discovered was a little surprising. In the absence of an ACPI reboot vector, Windows will hit the keyboard controller, wait a while, hit it again and then give up. If an ACPI reboot vector is present, windows will poke it, try the keyboard controller, poke the ACPI vector again and try the keyboard controller one more time."

Knowing this ended up being very useful. "This turns out to be important. The first thing it means is that it generates two writes to the ACPI reboot vector. The second is that it leaves a gap between them while it's fiddling with the keyboard controller. And, shockingly, it turns out that on most systems the ACPI reboot vector points at 0xcf9 in system IO space. Even though most implementations nominally require two different values be written, it seems that this isn't a strict requirement and the ACPI method works."

Now knowing this, Matthew adapted this reboot method to the Linux kernel and it's been integrated into the 3.0 kernel. Not only is it in this next kernel release, but it will be the default behavior. This blog post by Matthew has all of the details and he notes that this should fix the Linux reboot support for various Apple computers and ThinkPads, in particular.

The Linux 3.0 kernel may also solve the Linux kernel power regressions.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Linux Hardware Reviews
  1. Even With Re-Clocking, Nouveau Remains Behind NVIDIA's Proprietary Linux Driver
  2. The Power Consumption & Efficiency Of Open-Source GPU Drivers
  3. AMD R600g/RadeonSI Performance On Linux 3.16 With Mesa 10.3-devel
  4. Intel Pentium G3258 On Linux
Latest Linux Articles
  1. AMD Catalyst 14.6 Does Slightly Better With APITest OpenGL Tests
  2. Updated Source Engine Benchmarks On The Latest AMD/NVIDIA Linux Drivers
  3. Nouveau vs. Radeon vs. Intel Tests On Linux 3.16, Mesa 10.3-devel
  4. KVM Benchmarks On Ubuntu 14.10
Latest Linux News
  1. Belkin's WRT54G Router Successor Is Crap On The Software Front So Far
  2. QEMU 2.1 Officially Released
  3. XBMC Is Being Renamed To "Kodi"
  4. SteamOS Beta 126 Better Handles XBMC
  5. Ubuntu 14.10 Alpha 2 Released
  6. KDE 4.14 Release Candidate Ships
  7. Drivers & Drama Dominated Linux Talk In July
  8. Fedora Assembles A Security Team
  9. AMD Launches The A10-7800, The 65 Watt Kaveri
  10. Builder: A New Development IDE Being Built For GNOME
Latest Forum Discussions
  1. Updated and Optimized Ubuntu Free Graphics Drivers
  2. Grand Theft Auto Running On Direct3D Natively On Linux Shows Gallium3D Potential
  3. Linus Torvalds On GCC 4.9: Pure & Utter Crap
  4. Updated graphics drivers for Ubuntu 12.04 Precise LTS
  5. Debian + radeonsi
  6. AMD Publishes Open-Source Linux HSA Kernel Driver
  7. Open-source drivers on ATI R7 260X
  8. AMD Athlon 5350 APU On Linux