Initial 6.1 questions

Danial Thom danial_thom at
Mon Jun 12 14:21:05 UTC 2006

I'm just setting up to evaluate 6.1 for a
project, and before I tune I hoped to get some
feedback on why some things are the way they are.

first, why is the default for HZ now 1000? It
seems that 900 extra clock interrupts aren't a
performance enhancement.

Is there a reason that ITR isn't a tunable in the
em driver? It seems more usable generally to end
users than the delays.

Running a simple test with a traffic generator
(firing udp packets to a blackhole), the system
overhead with a single processor goes up from 10%
to 15% when running a kernel with SMP enabled
(and nothing else different). I have ITR set to
6000 interrupts per second. That seems like an
awful lot of overhead. Is there some problem
running an SMP-enabled kernel when only 1
processor is present, or is there really 50%
extra overhead on an SMP scheduler? I'll have a
dual core in a few days to test with.

Lastly, is there a utility similar to cpustat in
DragonflyBSD which shows the per-cpu usage stats?



Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 

More information about the freebsd-performance mailing list