CPU utilization

Robert Watson rwatson at FreeBSD.org
Thu Apr 12 10:46:30 UTC 2007

On Thu, 12 Apr 2007, Randall Stewart wrote:

> I have probably an old question that has been asked.. but here goes anyway.
> I have three machines.
> 1) stewart - running 7.0 (2.8gig p4 dual core)
> 2) bsd1    - running 7.0 (2.8gig Xeon Hyperthreaded)
> 3) bsd2    - running 6.2 (2.4gig Xeon Hyperthreaded)
> Now if I run tests that max out cpu (at least I think they do).. I see <1> 
> or <2> drag down to 1% idle/ even 0 %idle.
> However <3> never drops below 50% idle.. it preforms a lot slower too.. 
> which I expect since it is somewhat of an older processor.. but in running 
> say top -S

It strikes me that there are two possibilities here, and it could be both are 

(1) In 7.x, there are scheduling and accounting changes that could result in
     both better utilization and different measurement.

(2) In 7.x, certain debugging features default to on (WITNESS, INVARIANTS,
     user space malloc debugging) that add significant (!) overhead.

I'd confirm first that (2) isn't the cause of the change -- make sure you have 
a kernel without debugging features turned on, and change the man page on 
malloc.conf to make sure user debugging is turned off for malloc.  Then let's 
revisit (1).

Robert N M Watson
Computer Laboratory
University of Cambridge

> I see CPU 1 always running the idle process...
> Is this an accounting error that is being seen? aka top
> does not know how to display things .. or is this a
> scheduling error.. i.e.. move to 7.0 and life will
> be better :-D
> Thanks
> R
> -- 
> Randall Stewart
> NSSTG - Cisco Systems Inc.
> 803-345-0369 <or> 803-317-4952 (cell)
> _______________________________________________
> freebsd-current at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-current
> To unsubscribe, send any mail to "freebsd-current-unsubscribe at freebsd.org"

More information about the freebsd-current mailing list