Intermittent hangs in vmem_periodic()

[hiren panchasara]

I am seeing really weird system freeze for 2-3 seconds every minute or so.

% uname -a
FreeBSD flymockour-l7.corp.yahoo.com 10.0-CURRENT FreeBSD 10.0-CURRENT #2
r255423M: Mon Sep  9 12:29:22 PDT 2013     root at flymocko
ur-l7.corp.yahoo.com:/usr/obj/usr/home/hirenp/head/sys/GENERIC  amd64

Simple comands like "man top" hangs and this is what I see in ctrl+T
 % man top
 load: 1.59  cmd: zcat 76574 [*kmem arena] 2.16r 0.00u 1.82s 16% 2000k
 load: 1.70  cmd: zcat 76574 [*kmem arena] 7.19r 0.00u 1.82s 7% 2000k
 load: 1.89  cmd: zcat 76574 [*kmem arena] 12.58r 0.00u 1.82s 3% 2000k
 load: 1.90  cmd: zcat 76574 [*kmem arena] 14.58r 0.00u 1.82s 2% 2000k

I see similar things while trying to "exit" a terminal window.

I see following in pmcstat:

PMC: [INSTR_RETIRED_ANY] Samples: 117647 (100.0%) , 6885 unresolved

%SAMP CALLTREE
 75.9 fork_exit at kernel taskqueue_thread_loop taskqueue_run_locked
vmem_periodic(75.9%)

I am not running anything funny and I do not see anything weird in "top"
too.

Any help is appreciated.

cheers,
Hiren