preemtible Kernel

[Boris Glawe <public boris-glawe de>]

Hello,

From the introduction of kernel 2.6 on, the kernel can be configured to 
be preemtible. This promises better latency.

Many did not use this feature in the past: Why?

When I look at Fedora's 7 kernel source configuration (with 'make 
menuconfig'), the kernel is also not preemtible, but "voluntarily 
preemtible": What does that mean?

thanks and greets
Boris