Tribblix: manual page: cpustat.8

CPUSTAT(8) Maintenance Commands and Procedures CPUSTAT(8)

NAME

cpustat - monitor system behavior using CPU performance counters

SYNOPSIS

cpustat -c eventspec [-c eventspec]... [-p period] [-T u | d ]
[-sntD] [interval [count]]

cpustat -h

DESCRIPTION

The cpustat utility allows CPU performance counters to be used to
monitor the overall behavior of the CPUs in the system.

If interval is specified, cpustat samples activity every interval
seconds, repeating forever. If a count is specified, the statistics
are repeated count times. If neither are specified, an interval of
five seconds is used, and there is no limit to the number of samples
that are taken.

OPTIONS

The following options are supported:

-c eventspec

Specifies a set of events for the CPU performance counters to
monitor. The syntax of these event specifications is:

[picn=]eventn[,attr[n][=val]][,[picn=]eventn
[,attr[n][=val]],...,]

You can use the -h option to obtain a list of available events
and attributes. This causes generation of the usage message. You
can omit an explicit counter assignment, in which case cpustat
attempts to choose a capable counter automatically.

Attribute values can be expressed in hexadecimal, octal, or
decimal notation, in a format suitable for strtoll(3C). An
attribute present in the event specification without an explicit
value receives a default value of 1. An attribute without a
corresponding counter number is applied to all counters in the
specification.

The semantics of these event specifications can be determined by
reading the CPU manufacturer's documentation for the events.

Multiple -c options can be specified, in which case the command
cycles between the different event settings on each sample.

-D

Enables debug mode.

-h

Prints an extensive help message on how to use the utility and
how to program the processor-dependent counters.

-n

Omits all header output (useful if cpustat is the beginning of a
pipeline).

-p period

Causes cpustat to cycle through the list of eventspecs every
period seconds. The tool sleeps after each cycle until period
seconds have elapsed since the first eventspec was measured.

When this option is present, the optional count parameter
specifies the number of total cycles to make (instead of the
number of total samples to take). If period is less than the
number of eventspecs times interval, the tool acts as it period
is 0.

-s

Creates an idle soaker thread to spin while system-only
eventspecs are bound. One idle soaker thread is bound to each CPU
in the current processor set. System-only eventspecs contain both
the nouser and the sys tokens and measure events that occur while
the CPU is operating in privileged mode. This option prevents the
kernel's idle loop from running and triggering system-mode
events.

-T u | d

Display a time stamp.

Specify u for a printed representation of the internal
representation of time. See time(2). Specify d for standard date
format. See date(1).

-t

Prints an additional column of processor cycle counts, if
available on the current architecture.

USAGE

A closely related utility, cputrack(1), can be used to monitor the
behavior of individual applications with little or no interference
from other activities on the system.

The cpustat utility must be run by the super-user, as there is an
intrinsic conflict between the use of the CPU performance counters
system-wide by cpustat and the use of the CPU performance counters to
monitor an individual process (for example, by cputrack.)

Once any instance of this utility has started, no further per-process
or per-LWP use of the counters is allowed until the last instance of
the utility terminates.

The times printed by the command correspond to the wallclock time
when the hardware counters were actually sampled, instead of when the
program told the kernel to sample them. The time is derived from the
same timebase as gethrtime(3C).

The processor cycle counts enabled by the -t option always apply to
both user and system modes, regardless of the settings applied to the
performance counter registers.

On some hardware platforms running in system mode using the "sys"
token, the counters are implemented using 32-bit registers. While the
kernel attempts to catch all overflows to synthesize 64-bit counters,
because of hardware implementation restrictions, overflows can be
lost unless the sampling interval is kept short enough. The events
most prone to wrap are those that count processor clock cycles. If
such an event is of interest, sampling should occur frequently so
that less than 4 billion clock cycles can occur between samples.

The output of cpustat is designed to be readily parsable by nawk(1)
and perl(1), thereby allowing performance tools to be composed by
embedding cpustat in scripts. Alternatively, tools can be constructed
directly using the same APIs that cpustat is built upon using the
facilities of libcpc(3LIB). See cpc(3CPC).

The cpustat utility only monitors the CPUs that are accessible to it
in the current processor set. Thus, several instances of the utility
can be running on the CPUs in different processor sets. See psrset(8)
for more information about processor sets.

Because cpustat uses LWPs bound to CPUs, the utility might have to be
terminated before the configuration of the relevant processor can be
changed.

EXAMPLES

SPARC

Example 1: Measuring External Cache References and Misses

The following example measures misses and references in the external
cache. These occur while the processor is operating in user mode on
an UltraSPARC machine.

example% cpustat -c EC_ref,EC_misses 1 3

time cpu event pic0 pic1
1.008 0 tick 69284 1647
1.008 1 tick 43284 1175
2.008 0 tick 179576 1834
2.008 1 tick 202022 12046
3.008 0 tick 93262 384
3.008 1 tick 63649 1118
3.008 2 total 651077 18204

x86

Example 2: Measuring Branch Prediction Success on Pentium 4

The following example measures branch mispredictions and total branch
instructions in user and system mode on a Pentium 4 machine.

example% cpustat -c \
pic12=branch_retired,emask12=0x4,pic14=branch_retired,\
emask14=0xf,sys 1 3

time cpu event pic12 pic14
1.010 1 tick 458 684
1.010 0 tick 305 511
2.010 0 tick 181 269
2.010 1 tick 469 684
3.010 0 tick 182 269
3.010 1 tick 468 684
3.010 2 total 2063 3101

Example 3: Counting Memory Accesses on Opteron

The following example determines the number of memory accesses made
through each memory controller on an Opteron, broken down by internal
memory latency:

cpustat -c \
pic0=NB_mem_ctrlr_page_access,umask0=0x01, \
pic1=NB_mem_ctrlr_page_access,umask1=0x02, \
pic2=NB_mem_ctrlr_page_access,umask2=0x04,sys \
1

time cpu event pic0 pic1 pic2
1.003 0 tick 41976 53519 7720
1.003 1 tick 5589 19402 731
2.003 1 tick 6011 17005 658
2.003 0 tick 43944 45473 7338
3.003 1 tick 7105 20177 762
3.003 0 tick 47045 48025 7119
4.003 0 tick 43224 46296 6694
4.003 1 tick 5366 19114 652

WARNINGS

By running the cpustat command, the super-user forcibly invalidates
all existing performance counter context. This can in turn cause all
invocations of the cputrack command, and other users of performance
counter context, to exit prematurely with unspecified errors.

If cpustat is invoked on a system that has CPU performance counters
which are not supported by Solaris, the following message appears:

cpustat: cannot access performance counters - Operation not applicable

This error message implies that cpc_open() has failed and is
documented in cpc_open(3CPC). Review this documentation for more
information about the problem and possible solutions.

If a short interval is requested, cpustat might not be able to keep
up with the desired sample rate. In this case, some samples might be
dropped.

ATTRIBUTES

NOTES

When cpustat is run on a Pentium 4 with HyperThreading enabled, a CPC
set is bound to only one logical CPU of each physical CPU. See
cpc_bind_cpu(3CPC).

April 9, 2016 CPUSTAT(8)