misc/136759: iostat displays wrong I/O statistics with -c 1

[Vladimir Krasovsky]

>Number:         136759
>Category:       misc
>Synopsis:       iostat displays wrong I/O statistics with -c 1
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Jul 14 16:10:00 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Vladimir Krasovsky
>Release:        7.0
>Organization:
yandex.ru
>Environment:
FreeBSD host 7.0-STABLE FreeBSD 7.0-STABLE #1: Fri Feb 29 14:05:58 MSK 2008     root at host:/opt/obj/opt/src/sys/W5L_AMD64_ULE  amd64
>Description:
First line of iostat output always displays arbitrary (and wrong) numbers.
user at host:~$ for i in 1 2 3 4; do iostat -c $i -d da2; done
             da2 
  KB/t tps  MB/s 
  6.31  64  0.40 
             da2 
  KB/t tps  MB/s 
  6.31  64  0.40 
 12.64  53  0.65 
             da2 
  KB/t tps  MB/s 
  6.31  64  0.40 
  6.67  27  0.18 
  2.00  23  0.04 
             da2 
  KB/t tps  MB/s 
  6.31  64  0.40 
  2.00  23  0.04 
  3.27  11  0.04 
  7.25  16  0.11 

As you can see the first line is always the same. Though on different machines at different loads it may differ.
>How-To-Repeat:
for i in 1 2 3 4; do iostat -c $i -d da2; done
>Fix:
Use -c 2 or more.

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