KernelTrap: Debating Hertz

“The decision to change the default hertz in the 2.6 Linux
kernel from 1000 to 250 continued to be discussed, until Linux
creator Linus Torvalds finally had enough, ‘get on with your lives.
Realize that there is no ‘perfect’ value for HZ. 250 right now is
somewhere reasonable, and for the extreme ends you can always
choose your own.’ He also dismissed concern over picking an ideal
number that minimizes long-term time drift, ‘long-term time drift
is something that we inevitably have to use things like NTP to
handle, if you want an exact clock.’ Instead, he highlighted tasks
that affect the short term, such as converting timevals into
jiffies, ‘in short-term things, the timeval/jiffie conversion is
likely to be _bigger_ issue than the crystal frequency conversion.
So we should aim for a HZ value that makes it easy to convert to
and from the standard user-space interface formats. 100Hz, 250Hz
and 1000Hz are all good values for that reason. 864 is not…'”

Complete Story