ia64/183154: kernel{thread taskq} uses 100% CPU

[Anton Shterenlikht]

>Number:         183154
>Category:       ia64
>Synopsis:       kernel{thread taskq} uses 100% CPU
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-ia64
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Oct 21 11:40:01 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     Anton Shterenlikht
>Release:        FreeBSD 11.0-CURRENT ia64
>Organization:
University of Bristol	
>Environment:
FreeBSD mech-as28.men.bris.ac.uk 11.0-CURRENT FreeBSD 11.0-CURRENT #8 r256624: Wed Oct 16 15:06:04 BST 2013     root at mech-as28.men.bris.ac.uk:/usr/obj/usr/src/sys/ZEEV  ia64

	
>Description:

This host is extremely sluggish.
Periodically all activity seems to freeze
for 5-10-30 sec. For example, issuing ls, df, top
can lead to 10-20 sec. delay before the output
appears.

I noticed that the taskq thread is extremely busy,
sometimes at 100%:

last pid: 50628;  load averages:  1.01,  1.09,  1.31                        up 0+02:11:37  12:34:43
90 processes:  4 running, 69 sleeping, 15 waiting, 2 lock
CPU 0:  0.0% user,  0.0% nice, 31.6% system,  0.0% interrupt, 68.4% idle
CPU 1:  0.0% user,  0.0% nice, 68.8% system,  0.0% interrupt, 31.3% idle
Mem: 22M Active, 1072M Inact, 411M Wired, 1014M Buf, 8560M Free
Swap: 

  PID USERNAME   PRI NICE   SIZE    RES STATE   C   TIME     CPU COMMAND
    0 root         8    0     0K   416K CPU1    1  97:21 100.00% kernel{thread taskq}
   11 root       155 ki31     0K    64K RUN     0  75:53  79.69% idle{idle: cpu0}
   11 root       155 ki31     0K    64K RUN     1  71:38  18.90% idle{idle: cpu1}
   21 root        16    -     0K    32K *buffe  0   0:41   0.10% syncer
21873 root        20    0 14232K  5800K CPU0    0   0:09   0.10% top
    0 root       -16    0     0K   416K swapin  0   1:34   0.00% kernel{swapper}
   13 root        -8    -     0K    96K -       0   0:18   0.00% geom{g_down}

This is probably just a symptom of a deeper problem.

	
>How-To-Repeat:
	
>Fix:

	


>Release-Note:
>Audit-Trail:
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