ULE scheduler and the WCPU column in top

Nerius Landys nlandys at gmail.com
Thu Jul 22 22:32:39 UTC 2010

I have this interesting behavior in the top utility on _both_ my 7.1
and 8.0 FreeBSD servers (updated to latest patches).  The interesting
behavior happens only when my kernel is compiled with the ULE
scheduler.  It does not happen when the kernel uses the old BSD

Here is a link of a screenshot of top on one of my servers:
The output of top usually looks just like this, at most times of the
day.  The row that worries me is the process "ioUrTded.i3" run by the
user urt1, which is reported to be using 1.17% WCPU in the screenshot.
 It's the sixth row down.  The thing that makes no sense is that this
process is in fact using more CPU than any other process on my system,
and I know this as a fact.  The processes that are most active are all
video game servers, and the game server run by the urt1 user is the
most populated with the most going on, by far.  With my kernel
compiled to use the old BSD scheduler, the process run by urt1 is
_always_ the most active as reported by top; the WCPU shows between 30
and 40 percent on this process normally (with the BSD scheduler).

The WCPU percentage on the process owned by urt1 never reaches very
high - it always stays abnormally low as reported by top (with the ULE
scheduler).  The process itself is running just fine and the game
server is very busy.

Any ideas?  Is this a known issue when running the ULE scheduler?  Any
negative impacts that might occur?

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