Frequency vs. power consumption [meer-bezoekers.info]
Frequency, Resolution, and Power Consumption. To measure its own clock frequency, a digital system would typically feed its clock to a counter and Power consumption is also related to nominal frequency through the linear relationship. Most modern chips can run at lower clock than max, and while doing so, at a lower voltage, consuming less power and producing less heat. Contrary to popular. If I'm not mistaken, dynamic power is linearly proportional to clock to an extent, but not all systems adjust voltage with clock frequency. Posted Feb 27, 20 UTC (Mon) by PaulMcKenney (subscriber, #) [Link].
In laptops, the LCD 's backlight also uses a significant portion of overall power. While energy-saving features have been instituted in personal computers for when they are idle, the overall consumption of today's high-performance CPUs is considerable. This is in strong contrast with the much lower energy consumption of CPUs designed for low-power devices. There are some engineering reasons for this pattern. For a given device, operating at a higher clock rate may require more power.
Reducing the clock rate or undervolting usually reduces energy consumption; it is also possible to undervolt the microprocessor while keeping the clock rate the same.
Turning unused areas off saves energy, such as through clock gating. As a processor model's design matures, smaller transistors, lower-voltage structures, and design experience may reduce energy consumption. Processor manufacturers usually release two power consumption numbers for a CPU: When the CPU is idle, it will draw far less than the typical thermal power.
Datasheets normally contain the thermal design power TDPwhich is the maximum amount of heat generated by the CPU, which the cooling system in a computer is required to dissipate.
CPU power dissipation
This makes it hard to determine what an application will perform like on any particular platform. For me, this means that the only reasonable way to know about a thread's optimal runtime performance requirement is therefore to measure it while its running and age older measurements as we do with load measurement.
- Frequency vs. power consumption
Whether it is possible to do this in a generic enough manner that it could be accepted into a mainline Linux Kernel is IMO a different matter to the technical problem of doing the measurement and using those indications for something useful, and probably will take longer too: I think you and I likely agree that the system should run reasonably if nobody ever calls it in a typical application. It exists to help you take performance from "reasonable, if not quite optimal" to "stellar.
As you said, though, it's less clear if you're a web browser or office app. Although, I strongly suspect both are more cache thrashy than they'd like to be, even when idle.
clockspeed - How speed and frequency of a processor are related to each other? - Super User
That said, my madvise proposal above was partly tongue in cheek. It would be interesting though, to try to characterize apps by their recent cache miss ratios and use that to make CPU affinity selections as well as operating frequency selections. Actually, you need two ratios: You could have a fairly high miss ratio with a low stall ratio.
A faster CPU still helps you. A high miss ratio with a high stall ratio suggests a more serial program that's staying memory bound.