amd64/127451: incorrect load on quad core

[Miks]

>Number:         127451
>Category:       amd64
>Synopsis:       incorrect load on quad core
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-amd64
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Sep 17 21:50:01 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator:     Miks
>Release:        7.0 release amd64
>Organization:
skynet
>Environment:
FreeBSD sun 7.0-RELEASE-p4 FreeBSD 7.0-RELEASE-p4 #4: Thu Sep 11 22:08:16 EEST 2008     miks at sun:/usr/obj/usr/src/sys/SUN  amd64
>Description:
I got load average around 0.5, and top show something like this
"1021 processes: 1 running, 1020 sleeping
CPU states:  4.9% user,  0.0% nice,  3.6% system,  0.9% interrupt,
90.6% idle" - this all is ok.

then once in 2-5 minutes, there for 2-3 seconds are:
"1020 processes:67 running, 912 sleeping, 1 zombie, 40 lock
CPU states:  3.0% user,  0.0% nice, 96.7% system,  0.3% interrupt,
0.0% idle" - this is the problem.

after this load average is 20-30 and dropping in 2-3min to 0.5. during
this time system is very slow. even ssh session is freezing.
most of processes are fastcgi/php, so there is not one big resource
hungry process.

found similar problem here: http://unix.derkeiler.com/Mailing-Lists/FreeBSD/stable/2007-11/msg00551.html
>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: