Perfd implements a prototype a new power management framework. After APM and ACPI, there is now the Linux Performance Daemon.
The traditional method to manage the power on PCs, laptops, PDAs, and phones is to simply turn-off unused hardware. The biggest problem in this case is to detect when hardware is idle. The efficiency of this approach is limited. For instance, a hard-disk may need a few seconds to become active and therefore delays applications. Transmeta LongRun and Intel SpeedStep try to predict the CPU demand and predict the optimal clock frequency for the next 10 milliseconds. This approach causes problems for unpredictably loads, such as DVD playback.
The Perfd framework improves power management by breaking the transparency and providing applications with the opportunity to indicate their demands and preserve battery power. For instance, within Perfd a DVD decoder that knows the resources it needs to decode the current video frame can indicate this to the Perfd processor driver. A Perfd driver complements a device driver, by maximizing performance and power efficiency. Each Perfd driver includes a performance model of the hardware it controls. Such a performance models provides it with the intelligence to reduce power consumption. This model can also be queried by applications that are interested, for instance, in the current mJ/MByte of a wireless link. By breaking the abstraction, intelligent applications can reduce their power consumption and are no longer starved to information on abtract on 'eth0'.
This project has the following developers:
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