BUSSTAT(8) Maintenance Procedures BUSSTAT(8)


busstat - report bus-related performance statistics


busstat -e device-inst | -h | -l

busstat [-a] [-n]
[-w device-inst [,pic0=event,picn=event ]]...
[-r device-inst]... [interval [count]]


busstat provides access to the bus-related performance counters in the
system. These performance counters allow for the measurement of
statistics like hardware clock cycles, bus statistics including DMA and
cache coherency transactions on a multiprocessor system. Each bus device
that supports these counters can be programmed to count a number of
events from a specified list. Each device supports one or more
Performance Instrumentation Counters (PIC) that are capable of counting
events independently of each other.

Separate events can be selected for each PIC on each instance of these
devices. busstat summarizes the counts over the last interval seconds,
repeating forever. If a count is given, the statistics are repeated count

Only root users can program these counters. Non-root users have the
option of reading the counters that have been programmed by a root user.

The default value for the interval argument is 1 second, and the default
count is unlimited.

The devices that export these counters are highly platform-dependent and
the data may be difficult to interpret without an in-depth understanding
of the operation of the components that are being measured and of the
system they reside in.


The following options are supported:


Display absolute counter values. The default is delta values.

-e device-inst

Display the list of events that the specified device supports for
each pic.

Specify device-inst as device (name) followed by an optional instance
number. If an instance number is specified, the events for that
instance are displayed. If no instance number is specified, the
events for the first instance of the specified device are displayed.


Print a usage message.


List the devices in the system which support performance counters.


Do not display a title in the output. The default is to display

-r device-inst

Read and display all pic values for the specified device

Specify device-inst as device (name) followed by instance number, if
specifying an instance number of a device whose counters are to be
read and displayed. If all instances of this device are to be read,
use device (name) without an instance number. All pic values will be
sampled when using the -r option.

-w device-inst [,pic0=event] [,picn=event]

Program (write) the specified devices to count the specified events.
Write access to the counters is restricted to root users only. Non-
root users can use -r option.

Specify device-inst as device (name) followed by an optional instance
number. If specifying an instance number of a device to program these
events on. If all instances of this device are to be programmed the
same, then use device without an instance number. Specify an event to
be counted for a specified pic by providing a comma separated list of
picn=event values.

The -e option displays all valid event names for each device. Any
devices that are programmed will be sampled every interval seconds
and repeated count times. It is recommended that the interval
specified is small enough to ensure that counter wraparound will be
detected. The rate at which counters wraparound varies from device to
device. If a user is programming events using the -w option and
busstat detects that another user has changed the events that are
being counted, the tool will terminate as the programmed devices are
now being controlled by another user. Only one user can be
programming a device instance at any one time. Extra devices can be
sampled using the -r option. Using multiple instances of the -w
option on the same command line, with the same device-inst specifying
a different list of events for the pics will give the effect of
multiplexing for that device. busstat will switch between the list of
events for that device every interval seconds. Event can be a string
representing the event name, or even a number representing the bit
pattern to be programmed into the Performance Control Register (PCR).
This assumes explicit knowledge of the meaning of the control
register bits for a device. The number can be specified in
hexadecimal, decimal, or octal, using the usual conventions of


The following exit values are returned:

Successful completion.

An error occurred.

Another user is writing to the same devices.



Example 1: Programming and monitoring the Address Controller counters

In this example, ac0 refers to the Address Controller instance 0. The
counters are programmed to count Memory Bank stalls on an Ultra
Enterprise system at 10 second intervals with the values displayed in
absolute form instead of deltas.

# busstat -a -w ac0,pic0=mem_bank0_stall,pic1=mem_bank1_stall 10
time dev event0 pic0 event1 pic1
10 ac0 mem_bank0_stall 1234 mem_bank1_stall 5678
20 ac0 mem_bank0_stall 5678 mem_bank1_stall 12345
30 ac0 mem_bank0_stall 12345 mem_bank1_stall 56789

For a complete list of the supported events for a device, use the -e

Example 2: Programming and monitoring the counters on all instances of the

Address Controller

In this example, ac refers to all ac instances. This example programs all
instances of the Address Controller counters to count_clock cycles and
mem_bank0_rds at 2 second intervals, 100 times, displaying the values as

# busstat -w ac,pic0=clock_cycles,pic1=mem_bank0_rds 2 100
time dev event0 pic0 event1 pic1
2 ac0 clock_cycles 167242902 mem_bank0_rds 3144
2 ac1 clock_cycles 167254476 mem_bank0_rds 1392
4 ac0 clock_cycles 168025190 mem_bank0_rds 40302
4 ac1 clock_cycles 168024056 mem_bank0_rds 40580

Example 3: Monitoring the events being counted

This example monitors the events that are being counted on the sbus1
device, 100 times at 1 second intervals. It suggests that a root user has
changed the events that sbus1 was counting to be dvma_tlb_misses and
interrupts instead of pio_cycles.

% busstat -r sbus0 1 100

time dev event0 pic0 event1 pic1
1 sbus1 pio_cycles 2321 pio_cycles 2321
2 sbus1 pio_cycles 48 pio_cycles 48
3 sbus1 pio_cycles 49 pio_cycles 49
4 sbus1 pio_cycles 2281 pio_cycles 2281
5 sbus1 dvma_tlb_misses 0 interrupts 0
6 sbus1 dvma_tlb_misses 6 interrupts 2
7 sbus1 dvma_tlb_misses 8 interrupts 11

Example 4: Event Multiplexing

This example programs ac0 to alternate between counting (clock cycles,
mem_bank0_rds) and (addr_pkts, data_pkts) at 2 second intervals while
also monitoring what ac1 is counting :

It shows the expected output of the above busstat command. Another root
user on the machine has changed the events that this user had programmed
and busstat has detected this and terminates the command with a message.

# busstat -w ac0,pic0=clock_cycles,pic1=mem_bank0_rds \
-w ac0,pic0=addr_pkts,pic1=data_pkts \
-r ac1 2

time dev event0 pic0 event1 pic1
2 ac0 addr_pkts 12866 data_pkts 17015
2 ac1 rio_pkts 385 rio_pkts 385
4 ac0 clock_cycles 168018914 mem_bank0_rds 2865
4 ac1 rio_pkts 506 rio_pkts 506
6 ac0 addr_pkts 144236 data_pkts 149223
6 ac1 rio_pkts 522 rio_pkts 522
8 ac0 clock_cycles 168021245 mem_bank0_rds 2564
8 ac1 rio_pkts 387 rio_pkts 387
10 ac0 addr_pkts 144292 data_pkts 159645
10 ac1 rio_pkts 506 rio_pkts 506
12 ac0 clock_cycles 168020364 mem_bank0_rds 2665
12 ac1 rio_pkts 522 rio_pkts 522
busstat: events changed (possibly by another busstat).


strtol(3C), attributes(7), iostat(8), mpstat(8), vmstat(8)

November 1, 1999 BUSSTAT(8)