Intermittent hangs in vmem_periodic()

[Gleb Smirnoff]

On Wed, Sep 11, 2013 at 09:51:16PM -0700, hiren panchasara wrote:
h> I am seeing really weird system freeze for 2-3 seconds every minute or so.
h> 
h> % uname -a
h> FreeBSD flymockour-l7.corp.yahoo.com 10.0-CURRENT FreeBSD 10.0-CURRENT #2
h> r255423M: Mon Sep  9 12:29:22 PDT 2013     root at flymocko
h> ur-l7.corp.yahoo.com:/usr/obj/usr/home/hirenp/head/sys/GENERIC  amd64
h> 
h> Simple comands like "man top" hangs and this is what I see in ctrl+T
h>  % man top
h>  load: 1.59  cmd: zcat 76574 [*kmem arena] 2.16r 0.00u 1.82s 16% 2000k
h>  load: 1.70  cmd: zcat 76574 [*kmem arena] 7.19r 0.00u 1.82s 7% 2000k
h>  load: 1.89  cmd: zcat 76574 [*kmem arena] 12.58r 0.00u 1.82s 3% 2000k
h>  load: 1.90  cmd: zcat 76574 [*kmem arena] 14.58r 0.00u 1.82s 2% 2000k
h> 
h> I see similar things while trying to "exit" a terminal window.
h> 
h> I see following in pmcstat:
h> 
h> PMC: [INSTR_RETIRED_ANY] Samples: 117647 (100.0%) , 6885 unresolved
h> 
h> %SAMP CALLTREE
h>  75.9 fork_exit at kernel taskqueue_thread_loop taskqueue_run_locked
h> vmem_periodic(75.9%)

You probably got DIAGNOSTIC in your kernel config.

-- 
Totus tuus, Glebius.