SCHED_ULE on desktop system

Hello,

I'm curious if SCHED_ULE is designed to be used on a desktop system. I'm
running -CURRENT at home and tried to use SCHED_ULE for some time. It
works alright while the load is not very high. But once I start
compiling something (running 'make buildworld' or 'portupgrade -a' for
example), the machine comes almost unusable - X11's windows takes a lot
of time to redraw, changing virtual desktop in window manager may take
a several seconds. And it's nearly impossible to watch some movie with
mplayer. 

However, when I switch to SCHED_4BSD, system's reaction time gets lower
and I even can watch a movie with mplayer when compiling something.

Is SHCED_ULE designed to behave that way or I spotted some bug?

PS I run UP system.

Roman Bogorodskiy