kern/84957: fire_saver.ko causes high CPU usage by swi5

Nick Johnson freebsd at
Mon Aug 15 16:00:31 GMT 2005

>Number:         84957
>Category:       kern
>Synopsis:       fire_saver.ko causes high CPU usage by swi5
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Aug 15 16:00:28 GMT 2005
>Originator:     Nick Johnson
>Release:        FreeBSD 5.4-STABLE i386
System: FreeBSD 5.4-STABLE FreeBSD 5.4-STABLE #2: Mon Aug 15 08:31:15 PDT 2005     root at  i386


I noticed, surprisingly high user CPU usage (circa 35%) when the machine was completely idle.  top -S showed
that all of that 35% was going to swi5: clock sio.  This was also driving the system load at idle up to 0.40 

After mucking about with various kernel configuration options I noticed that after rebooting the usage of swi5
was reasonable for several minutes and then jumped up to 35%.  It was then that I thought of checking to see if 
I had configured a screen saver to load, and sure enough, I had fire_saver.ko loaded.

Unloading fire_saver.ko sent the usage of swi5 back down to 0%.  I suspect somewhere in fire_saver.ko one might
find ugliness.

Load fire_saver.ko.  Wait for it to start.  top -S

kldunload fire_saver.ko


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