Constant TIMER_FREQ

pub const TIMER_FREQ: u64 = 1000;

The timer frequency in Hz.

Here we choose 1000Hz since 1000Hz is easier for unit conversion and convenient for timer. What’s more, the frequency cannot be set too high or too low, 1000Hz is a modest choice.

For system performance reasons, this rate cannot be set too high, otherwise most of the time is spent in executing timer code.