i386/79943: Very High interupt rate on PCM

Thu Apr 14 16:40:23 PDT 2005

>Number:         79943
>Category:       i386
>Synopsis:       Very High interupt rate on PCM
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-i386
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Apr 14 23:40:22 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     Christopher T. Johnson
>Release:        FreeBSD 5.3-RELEASE-p2 i386
>Organization:
>Environment:
System: FreeBSD fam.cyberpaladin.com 5.3-RELEASE-p2 FreeBSD 5.3-RELEASE-p2 #0: Mon Dec 20 16:25:48 EST 2004 root at fam.cyberpaladin.com:/usr/obj/usr/src/sys/GENERIC i386
686 CPU with HT, Alienware laptop.  NVIDIA graphics card
>Description:
When I was doing a port build from sourt I noticed that the system was very
slow.  Slower than expected.  I used systat -vmstat to verify the system
usage.  I noticed that IRQ 18 (PCM) was running at 28,000+ interupts per
second.

My most recent change was to have used portinstall to install the nvidia
drivers.

With some experements I discovered that when nvidia.ko is loaded with OUT
snd_ich.ko (and sound.ko) I have not interupt storms.  If snd_ich.ko is
loaded with OUT nvidia.ko, I get no interupt storms.  It is the combination
of the two.

On a basicly idle system, the interupts are consuming 10% of system time
and 15% of Interupt time.
>How-To-Repeat:

Load nvidia.ko and snd_ich.ko and start X windows.
>Fix:
work around: Don't load both sound and nvidia drivers at the same time.

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