kern/183753: Regression since r255138: network is slow, kernel: failed to create new mbuf

[Ralf Wenk]

>Number:         183753
>Category:       kern
>Synopsis:       Regression since r255138: network is slow, kernel: failed to create new mbuf
>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:   Thu Nov 07 15:20:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     Ralf Wenk
>Release:        FreeBSD 10.0-CURRENT arm
>Organization:
Hochschule Karlsruhe, University of Applied Sciences
>Environment:
FreeBSD raspberry-pi 10.0-CURRENT FreeBSD 10.0-CURRENT #0 r255138: Wed Nov  6 08:42:26 CET 2013     root at IZ-FreeBSD1:/usr/obj/arm.armv6/root/rpi/255138/sys/RPI-Bsc  arm
>Description:
While rsync(1)-ing an 1 GB file the RPi gets almost unresponsible after a
while and on the serial console there are lots of

  smsc0: warning: failed to create new mbuf

kernel messages. Occasionaly dotted with the

  [zone: mbuf_cluster] kern.ipc.nmbclusters limit reached

kernel message.

rsync shows a transfer speed of 27.40kB/s (over DSL) even if the files are
already in sync and only the timestamps differ.

Increasing the value of kern.ipc.nmbclusters by the factor of 2 just delayed
the moment the problem happens.

The first release which shows this is r25518. r255166 and older do not.

rsync shows a transfer speed of 535.46kB/s (over DSL) on r255166 and older
releases.
>How-To-Repeat:
Use a 1GB file as transfer file.
If already transfered touch(1) transfer file at the source host.

rsync -trv --modify-window=1 --compress --progress --stats --inplace --delete transfer_file user at target.host:/path/to/

Await problem around 10% of the file is transfered.
>Fix:
Undo r255138.

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