[ Previous |
AIX Version 4.3 Commands Reference, Volume 3
Displays simple and complex lock
lockstat [ -a ][ -c LockCount ] [ -b BlockRatio ] [ -n CheckCount ] [ -p LockRate ]
MaxLocks ] [ Interval [Count ] ]
Note: To enable lock
statistics collection, the bosboot -L command must be
The lockstat command
reports statistics about contention in the operating system among
simple and complex kernel locks. Reports generated by the lockstat
command can be used to ensure that system performance is not
being reduced by excessive lock contention.
The lockstat command
generates a report for each kernel lock which meets all the
specified conditions. If no condition values are specified,
default conditions are used. The reports give information about
the number of lock requests for each lock. A lock request is a
lock operation (such as taking or upgrading a lock) which in some
cases cannot be satisfied immediately. A lock request which
cannot be satisfied at once is said to block. A blocked request
will either spin (repeatedly execute instructions which do
nothing) or sleep (allowing another thread to execute).
The column headings in the lockstat
command listing have the following meanings:
- The subsystem to which the lock belongs.
- The symbolic name of the lock class.
- The occurrence number of the lock in its class.
- The reference rate, or number of lock requests per
- The reference rate expressed as a percentage of all lock
- The ratio of blocking lock requests to total lock
requests. A block occurs whenever the lock cannot be
- The percentage of lock requests which cause the calling
thread to sleep.
- Displays a supplementary list showing the most requested
(or active) locks, regardless of the conditions defined
by other flags.
- -c LockCount
- Specifies how many times a lock must be requested during
an interval in order to be displayed. The default value
of the LockCount parameter is 200.
- -b BlockRatio
- Specifies a block ratio. A lock must have a block ratio
which is higher than the specified BlockRatio
parameter in order to be listed. The default value of the
BlockRatio parameter is five percent.
- -n CheckCount
- Specifies the number of locks which are to be checked.
The lockstat command sorts locks according to lock
activity. The CheckCount parameter determines how
many of the most active locks will be subject to further
checking. Limiting the number of locks which are checked
maximizes system performance, particularly if the Count
parameter is used to run the lockstat command
repeatedly. By default, the 40 most active locks are
- -p LockRate
- Specifies a percentage of the activity of the
most-requested lock in the kernel. Only locks which are
more active than this will be listed. The default LockRate
value is two, meaning that the only locks listed are
those requested at least two percent as often as the most
active lock. Note that LockRate
is not the
same concept as the %Ref
field, which is
relative to the total number of lock requests.
- -t MaxLocks
- Specifies the maximum number of locks to be displayed.
The default is to list up to 10 locks.
- Specifies the amount of time in seconds between each
report. Each report contains statistics collected during
the interval since the previous report. If the Interval
parameter is not specified, the lockstat command
generates a single report covering an interval of one
second and then exits.
- Determines the number of reports generated. The Count
parameter can only be specified with the Interval
parameter. If the Interval parameter is specified
without the Count parameter, reports are
continuously generated. A Count parameter of 0 is
- To generate a single lock
statistic report based on default conditions, enter:
The output is similar to:
Subsys Name Ocn Ref/s %Ref %Block %Sleep
PROC PROC_LOCK_CLASS 2 1442 3.06 6.98 0.75
PROC PROC_INT_CLASS 1 1408 2.98 5.86 1.77
IOS IOS_LOCK_CLASS 4 679 1.44 5.19 2.29
- To generate 100 lock
statistic reports at one second intervals, displaying
only those locks which are more than 50 percent as active
as the most active lock, enter:
50 1 100
- Contains the lockstat command.
The iostat command, vmstat command, and the bosboot command.
The dlock subcommand for the crash
The /dev/kmem special file.
[ Previous |