VL-Hot: A Non-polling Alternative To HAL

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Software

In most current Linux distributions if you plug in a piece of removable media, anything ranging from a USB memory stick to a removable hard drive to a memory card, an icon pops up on the desktop and/or a file manager window opens. The same thing happens if you insert a CD-ROM or DVD-ROM into a drive. This is accomplished by the HAL (Hardware Abstraction Layer) daemon which continually polls the hardware to determine if anything has been added or removed. Generally this works very well and makes the Linux desktop decidedly more user friendly than it was in the days before HAL.

As is usually the case this additional functionality and friendliness comes with a cost. Continuous querying to check for new or removed hardware consumes CPU cycles and energy. On older, legacy hardware or any system with limited processing power, including the lowest end of today's netbooks, using HAL can actually impact system performance in a noticeable way. On battery operated systems it also translates into somewhat shorter battery life. For those interested in green computing and reducing energy consumption the continuous polling activity by the HAL daemon when no hardware changes take place is simply wasteful.

VL-Hot, developed for Vector Linux provides an alternative that doesn't require continuous hardware polling. Instead VL-Hot uses udev triggers to pop up the required icons. The Vector Linux developers have VL-Hot working with lightweight window managers like JWM and IceWM provided that the PCMan File Manager is installed. I'm actually quite surprised that other distributions which aim to be lightweight haven't incorporated VL-Hot.

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