An LWN.net article describes how two Intel engineers got an Asus Eee PC (pictured) to boot to a graphical Linux desktop in five seconds. The boot system is based on modified software loads from Fedora and Moblin, says the article.

The five-second boot of a Fedora distribution on the Asus Eee PC netbook — some nine times faster than a typical Fedora boot — was demonstrated at the recent Linux Plumbers Conference (LPC) in Portland, Oregon, says the article, written by Don Marti.

The system was developed by two Intel developers:

• Arjan van de Ven, the author of PowerTop
• Auke Kok, a developer at Intel's Open Source Technology Center

Using the Bootchart application, which graphs each element of the boot process, the developers were said to have demonstrated why a Fedora boot-up takes 45 seconds (and Ubuntu 43 seconds). Precious seconds are wasted, the developers reportedly showed the audience, on tasks such as starting the loopback device for checking network interfaces, starting “sendmail,” and running other programs that most people don't regularly use, such as “setroubleshootd” for Security Enhanced Linux (SELinux) configuration troubleshooting. (And don't get them “started” on splash screens!)

To break the five-second barrier, the developers first reduced kernel start-up to a single second, including all module start-ups. An “early boot,” which includes init scripts and background tasks, was then allotted another second. X was given another second, and the desktop environment received a generous two seconds. The developers dispensed with initrd because it consumes a half second, and with the above modules already loaded, is not necessary in 95 percent of laptops, the developers were quoted as saying. The team also performed asynchronous initialization of some kernel subsystems, writes Marti.

sReadahead to the rescue

The “secret sauce” of the five-second trick appears to be a small patch the Intel team developed to support read-ahead operations. The group's sReadahead is a modified version of Fedora Readahead. According to the article, sReadahead is being submitted to Moblin.org, the Intel sponsored open source group that has developed the Moblin mobile development stack aimed at mobile Intenet devices (MIDs) and netbooks.

Instead of using Fedora's Upstart initialization program, the Intel team went back to the original init, modifying it to perform the following tasks simultaneously:

• “sReadahead” process
• Implement the critical path: filesystem check
• Start D-Bus inter-process communications

Subsequent steps in the five-second boot are said to include:

• Launch X and the desktop
• Start the Hardware Abstraction Layer (HAL)
• Launch the udev manager for hot-plugged devices

The Intel developers contend that distributions should not be forced to maintain separate initrd-based and initrd-free kernel packages. “Make it so you only pay the price if you use the feature,” Arjan was quoted as saying.

Availability

The full LWN.net article, “LPC: Booting Linux in five seconds,” including Bootchart graphs, should be available here.

 
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