kern/82271: cbq scheduler cause bad latency

[Sebastian Koehler]

>Number:         82271
>Category:       kern
>Synopsis:       cbq scheduler cause bad latency
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Jun 15 14:10:05 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     Sebastian Koehler
>Release:        5.4-STABLE
>Organization:
>Environment:
FreeBSD icecube.thrillkill.lan 5.4-STABLE FreeBSD 5.4-STABLE #10: Fri Jun 10 13:52:40 CEST 2005     acex5 at icecube.thrillkill.lan:/usr/obj/usr/src/sys/ICECUBE  i386
>Description:
The following altq rule cause a bad latency from all internal clients using my router.

altq on $int_if cbq    bandwidth 2Mb queue { std_in, wow_in }
  queue std_in         bandwidth 128Kb priority 1 cbq(default)
  queue wow_in         bandwidth 1920Kb priority 4 { wow_std_in, wow_pri_in }
    queue wow_std_in   bandwidth 1792Kb priority 4 cbq(borrow)
    queue wow_pri_in   bandwidth 128Kb  priority 7 cbq(borrow)

This effect only occurs, when the internal interface is used. If I use priq on internal interface, latency looks good, too.

altq on $ext_if priq bandwidth 2Mb queue { std_out, wow_std_out, wow_pri_out }
  queue std_out priq(default)
  queue wow_std_out priority 5 priq(red)
  queue wow_pri_out priority 6

Without cbq rule on internal interface:
Antwort von 66.249.85.99: Bytes=32 Zeit=17ms TTL=247
Antwort von 66.249.85.99: Bytes=32 Zeit=16ms TTL=247
Antwort von 66.249.85.99: Bytes=32 Zeit=18ms TTL=247

With cbq rule on internal interface:
Antwort von 66.249.85.99: Bytes=32 Zeit=16ms TTL=247
Antwort von 66.249.85.99: Bytes=32 Zeit=18ms TTL=247
Antwort von 66.249.85.99: Bytes=32 Zeit=17ms TTL=247

With cbq rule on internal interface and traffic from an internal client (http, online stream etc.)
Antwort von 66.249.85.99: Bytes=32 Zeit=1619ms TTL=247
Antwort von 66.249.85.99: Bytes=32 Zeit=4029ms TTL=247
Antwort von 66.249.85.99: Bytes=32 Zeit=1979ms TTL=247

The issue doesn't seems to be architecture related, cause the issue happen on FreeBSD 5.4-STABLE on Sparc64, too.
>How-To-Repeat:
Load the altq rule into pf. Create traffic from an internal client and check latency from same or other host.
>Fix:
n/a
>Release-Note:
>Audit-Trail:
>Unformatted: