Applications Power Management

Avoid Polling

Most of the applications in use today were first implemented on a kernel with periodic tick. Those applications have an implicit assumption that the kernel will wake up, on each CPU, multiple times in a second. As a result, periodic polling seems to have become an easy, simple solution for many application problems. Every time an application polls for something, the CPU wakes from idle state, wasting power.

But, with the tickless idle feature, there is no periodic tick on an idle CPU.

Some examples of how applications perform unnecessary polling include (Yes. They are real world applications):

• Checking every second to see if the mouse moved
• Check every second to see if it is time to show the next minute on the clock
• Check 10x/sec to see if the sound volume has changed
• Check 10x/sec to see if the smartcard reader got inserted on USB
• Check 10,000x/sec to see if there is data in the pipe