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From: "Joerg Lehners" <Joerg.Lehners@Informatik.Uni-Oldenburg.DE>
To: FreeBSD-gnats-submit@freebsd.org
Cc:
Subject: kernel 'options DEVICE_POLLING' makes loadavg wrong
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>Number:         92023
>Category:       kern
>Synopsis:       [kernel] 'options DEVICE_POLLING' makes loadavg wrong
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Jan 19 21:30:04 GMT 2006
>Closed-Date:    
>Last-Modified:  Sat Mar 17 16:50:07 GMT 2007
>Originator:     Joerg Lehners
>Release:        FreeBSD 6.0-STABLE i386
>Organization:
ARBI, Dept. Informatik, Fk II, University of Oldenburg
>Environment:
FreeBSD testido2 6.0-STABLE FreeBSD 6.0-STABLE #2: Thu Jan 19 22:05:47 MET 2006     root@testido2:/usr/src/sys/i386/compile/JL-TESTIDO2  i386

	Joe Avgs i386 PC with 6.0-STABLE as of 12. January 2006

>Description:

	Add the line
		options        DEVICE_POLLING
	to the kernel config file, compile and boot this kernel,
	start one program like 'main () { while (1) { } }' on the otherwise
	idle machine and watch the load avg. climbing above 1 and eventually
	reaching 2.
	For the counter test remove the options DEVICE_POLLING line
	and watch the load avg. reaching 1 for the same test.

>How-To-Repeat:
	
	See above

>Fix:

	Don't know, I'm no kernel hacker yet.


>Release-Note:
>Audit-Trail:

From: Harrison Grundy <astrodog@gmail.com>
To: bug-followup@FreeBSD.org,  Joerg.Lehners@Informatik.Uni-Oldenburg.DE
Cc:  
Subject: Re: kern/92023: [kernel] 'options DEVICE_POLLING' makes loadavg wrong
Date: Sat, 17 Mar 2007 04:38:44 -0500

 This would appear to be unavoidable with polling, because of what the 
 load average represents. Since it only shows the number of things 
 waiting to run (or, number of things on the run queue),  polling would 
 be expected to cause this behavior.

From: Bruce Evans <bde@zeta.org.au>
To: Harrison Grundy <astrodog@gmail.com>
Cc: freebsd-gnats-submit@freebsd.org
Subject: Re: kern/92023: [kernel] 'options DEVICE_POLLING' makes loadavg
 wrong
Date: Sun, 18 Mar 2007 03:45:06 +1100 (EST)

 On Sat, 17 Mar 2007, Harrison Grundy wrote:
 
 > This would appear to be unavoidable with polling, because of what the
 > load average represents. Since it only shows the number of things
 > waiting to run (or, number of things on the run queue),  polling would
 > be expected to cause this behavior.
 
 This behaviour (load average 2 with just 1 hog process) happens with
 polling configured on no devices, and even with no devices capable of
 supporting polling, but misbehaviour doesn't happen with 0 hog processes
 (then the load average is 0).  Why would polling be expected to do
 that?
 
 I didn't know that polling is what causes this.  It is very old
 misbehaviour (happens in pre-5.2).
 
 Bruce
>Unformatted:
