kern/92023: [kernel] 'options DEVICE_POLLING' makes loadavg wrong

[Bruce Evans]

The following reply was made to PR kern/92023; it has been noted by GNATS.

From: Bruce Evans <bde at zeta.org.au>
To: Harrison Grundy <astrodog at gmail.com>
Cc: freebsd-gnats-submit at 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