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iopending(1)                    USER COMMANDS                   iopending(1)




NAME

       iopending - plot number of pending disk events. Uses DTrace.


SYNOPSIS

       iopending  [-c]  [-d  device]  [-f filename] [-m mount_point] [interval
       [count]]


DESCRIPTION

       This samples the number of disk events that are  pending  and  plots  a
       distribution graph. By doing this the "serialness" or "parallelness" of
       disk behaviour can be distinguished.  A high  occurance  of  a  pending
       value of more than 1 is an indication of saturation.

       Since  this  uses  DTrace, only users with root privileges can run this
       command.


OPTIONS

       -c     clear screen

       -d device
              instance name to snoop (eg, dad0)

       -f filename
              full pathname of file to snoop

       -m mount_point
              mountpoint for filesystem to snoop


EXAMPLES

       Default output, print I/O summary every 1 second,
              # iopending


       Print 10 second samples,
              # iopending 10


       Print 12 x 5 second samples,
              # iopending 5 12


       Snoop events on the root filesystem only,
              # iopending -m /



FIELDS

       value  number of pending events, 0 == idle

       count  number of samples @ 1000 Hz

       load   1 min load average

       disk_r total disk read Kb for sample

       disk_w total disk write Kb for sample



IDEA

       Dr Rex di Bona



DOCUMENTATION

       See the DTraceToolkit for further documentation under the  Docs  direc-
       tory. The DTraceToolkit docs may include full worked examples with ver-
       bose descriptions explaining the output.


EXIT

       iopending will run forever until Ctrl-C is hit, or the specified  count
       is reached.


AUTHOR

       Brendan Gregg [Sydney, Australia]


SEE ALSO

       iosnoop(1M), iotop(1M), dtrace(1M)




version 0.60                     Nov 01, 2005                    iopending(1)

Mac OS X 10.6 - Generated Thu Sep 17 20:07:55 CDT 2009
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