kern/43159: ugen(1) isoc data loss

[jakllsch%kollasch.net@localhost]

>Number:         43159
>Category:       kern
>Synopsis:       ugen(1) isoc highbandwidth data loss
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Tue Apr 13 19:05:00 +0000 2010
>Originator:     Jonathan A. Kollasch
>Release:        NetBSD 5.0_STABLE
>Organization:
        
>Environment:
        
        
System: NetBSD siwenna.kollasch.net 5.0_STABLE NetBSD 5.0_STABLE (SIWENNA) #8: 
Mon Apr 12 17:52:44 UTC 2010 
root%siwenna.kollasch.net@localhost:/local/siwenna/20100403/src/sys/arch/i386/compile/SIWENNA
 i386
Architecture: i386
Machine: i386
>Description:
ugen(4) isn't tuned to handle high bandwidth isochronous pipes. 
>How-To-Repeat:
Use ugen(4) to read a 19+Mbit/s stream on a isochronous pipe,
note the missing data.
>Fix:
Maybe something like:

#define UGEN_NISOFRAMES 500
#define UGEN_NISOREQS  8
#define UGEN_NISORFRMS 32

or

#define UGEN_NISOFRAMES 250
#define UGEN_NISOREQS  6
#define UGEN_NISORFRMS 64

These parameters seem to result in a complete data set.

>Unformatted: