zfs recv hangs in kmem arena on STABLE10

[James R. Van Artsdalen]

FreeBSD BLACKIE.housenet.jrv 10.1-BETA2 FreeBSD 10.1-BETA2 #2 r272070M:
Wed Sep 24 17:36:56 CDT 2014    
james at BLACKIE.housenet.jrv:/usr/obj/usr/src/sys/GENERIC  amd64

With current STABLE10 I am unable to replicate a ZFS pool using zfs
send/recv without zfs hanging in state "kmem arena", within the first
4TB or so (of a 23TB Pool).

The most recent attempt used this command line

SUPERTEX:/root# zfs send -R BIGTEX/UNIX at syssnap | ssh BLACKIE zfs recv
-duvF BIGTOX

though local replications fail in kmem arena too.

The two machines I've been attempting this on have 16BG and 32GB of RAM
each and are otherwise idle.

Any suggestions on how to get around, or investigate, "kmem arena"?

# top
last pid:  3272;  load averages:  0.22,  0.22,  0.23                  up
0+08:25:02  01:32:07
34 processes:  1 running, 33 sleeping
CPU:  0.0% user,  0.0% nice,  0.1% system,  0.0% interrupt, 99.9% idle
Mem: 21M Active, 82M Inact, 15G Wired, 28M Cache, 450M Free
ARC: 12G Total, 24M MFU, 12G MRU, 23M Anon, 216M Header, 47M Other
Swap: 16G Total, 16G Free

  PID USERNAME    THR PRI NICE   SIZE    RES STATE   C   TIME    WCPU
COMMAND
 1173 root          1  52    0 86476K  7780K select  0 124:33   0.00% sshd
 1176 root          1  46    0 87276K 47732K kmem a  3  48:36   0.00% zfs
  968 root         32  20    0 12344K  1888K rpcsvc  0   0:13   0.00% nfsd
 1009 root          1  20    0 25452K  2864K select  3   0:01   0.00% ntpd
...