原文如下: The HZ will affect the timer granularity. For example at 250Hz, the granularity of each tick is 1000/250 = 4ms. But for 256 it is some weird non-integer number, 1000/256 =3.90625. You can see this is some of the schedulers, for example the CFQ scheduler tuning, with the default HZ=256 when you adjust any ms timing parameters, it rounds to steps of 3.9ms but with 250Hz, its in steps of 4ms. Also, 250Hz is the default for Linux.