powermetrics(1)              General Commands Manual             powermetrics(1)


     powermetrics [-i sample_interval_ms] [-r order] [-t wakeup_cost]
                  [-o output_file] [-n sample_count]

     powermetrics gathers and display CPU usage statistics (divided into time
     spent in user mode and supervisor mode), timer and interrupt wakeup
     frequency (total and, for near-idle workloads, those that resulted in
     package idle exits), and on supported platforms, interrupt frequencies
     (categorized by CPU number), package C-state statistics (an indication of
     the time the core complex + integrated graphics, if any, were in low-power
     idle states), as well as the average execution frequency for each CPU when
     not idle.

     -h, --help
             Print help message.

     -s samplers, --samplers samplers
             Comma separated list of samplers and sampler groups. Run with -h to
             see a list of samplers and sampler groups. Specifying "default"
             will display the default set, and specifying "all" will display all
             supported samplers.

     -o file, --output-file file
             Output to file instead of stdout.

     -b size, --buffer-size size
             Set output buffer size (0=none, 1=line)

     -i N, --sample-rate N
             sample every N ms (0=disabled) [default: 5000ms]

     -n N, --sample-count N
             Obtain N periodic samples (0=infinite) [default: 0]

     -t N, --wakeup-cost N
             Assume package idle wakeups have a CPU time cost of N us when using
             hybrid sort orders using idle wakeups with time-based metrics

     -r method, --order method
             Order process list using specified method [default: composite]

                   process identifier
                   total package idle wakeups (alias: -W)
                   total CPU time used (alias: -C)
                   energy number, see --show-process-energy (alias: -O)

     -f format, --format format
             Display data in specified format [default: text]

                   human-readable text output
                   machine-readable property list, NUL-separated

     -a N, --poweravg N
             Display poweravg every N samples (0=disabled) [default: 10]

             Hide CPU duty cycle data

             Print initial sample for entire uptime

             Print final usage summary when exiting

             Show pstate distribution. Only available on certain hardware.

             Show plimits, forced idle and RMBS. Only available on certain

             Show per cpu QOS breakdowns.

             Group processes by coalitions and show per coalition information.
             Processes that have exited during the sample will still have their
             time billed to the coalition, making this useful for disambiguating
             DEAD_TASK time.

             Show responsible pid for xpc services and parent pid

             Show per-process sfi wait time info

             Show per-process qos latency and throughput tier

             Show per-process io information

             Show per-process gpu time. This is only available on certain

             Show per-process network information

             Show QOS times aggregated by process. Per thread information is not

             Show per-process energy impact number. This number is a rough proxy
             for the total energy the process uses, including CPU, GPU, disk io
             and networking. The weighting of each is platform specific.
             Enabling this implicitly enables sampling of all the above per-
             process statistics.

             Show CPU time normailzed by the sample window, rather than the
             process start time. For example a process that launched 1 second
             before the end of a 5 second sample window and ran continuously
             until the end of the window will show up as 200 ms/s here and 1000
             ms/s in the regular column.

             Enables all samplers and displays all the available information for
             each sampler.

     This tool also implements special behavior upon receipt of certain signals
     to aid with the automated collection of data:

           take an immediate sample
           flush any buffered output
           stop sampling and exit

     Guidelines for energy reduction

     CPU time, deadlines and interrupt wakeups: Lower is better

     Interrupt counts: Lower is better

     C-state residency: Higher is better

     Running Tasks

     1. CPU time consumed by threads assigned to that process, broken down into
     time spent in user space and kernel mode.

     2. Counts of "short" timers (where the time-to-deadline was < 5
     milliseconds in the future at the point of timer creation) which woke up
     threads from that process. High frequency timers, which typically have
     short time-to-deadlines, can result in significant energy consumption.

     3. A count of total interrupt level wakeups which resulted in dispatching a
     thread from the process in question. For example, if a thread were blocked
     in a usleep() system call, a timer interrupt would cause that thread to be
     dispatched, and would increment this counter. For workloads with a
     significant idle component, this metric is useful to study in conjunction
     with the package idle exit metric reported below.

     4. A count of "package idle exits" induced by timers/device interrupts
     which awakened threads from the process in question. This is a subset of
     the interrupt wakeup count. Timers and other interrupts that trigger
     "package idle exits" have a greater impact on energy consumption relative
     to other interrupts. With the exception of some Mac Pro systems, Mac and
     iOS systems are typically single package systems, wherein all CPUs are part
     of a single processor complex (typically a single IC die) with shared logic
     that can include (depending on system specifics) shared last level caches,
     an integrated memory controller etc. When all CPUs in the package are idle,
     the hardware can power-gate significant portions of the shared logic in
     addition to each individual processor's logic, as well as take measures
     such as placing DRAM in to self-refresh (also referred to as auto-refresh),
     place interconnects into lower-power states etc. Hence a timer or interrupt
     that triggers an exit from this package idle state results in a a greater
     increase in power than a timer that occurred when the CPU in question was
     already executing. The process initiating a package idle wakeup may also be
     the "prime mover", i.e. it may be the trigger for further activity in its
     own or other processes. This metric is most useful when the system is
     relatively idle, as with typical light workloads such as web browsing and
     movie playback; with heavier workloads, the CPU activity can be high enough
     such that package idle entry is relatively rare, thus masking package idle
     exits due to the process/thread in question.

     5. If any processes arrived and vanished during the inter-sample interval,
     or a previously sampled process vanished, their statistics are reflected in
     the row labeled "DEAD_TASKS". This can identify issues involving transient
     processes which may be spawned too frequently. dtrace ("execsnoop") or
     other tools can then be used to identify the transient processes in
     question. Running powermetrics in coalition mode, (see below), will also
     help track down transient process issues, by billing the coalition to which
     the process belongs.

     Interrupt Distribution

     The interrupts sampler reports interrupt frequencies, classified by
     interrupt vector and associated device, on a per-CPU basis. Mac OS
     currently assigns all device interrupts to CPU0, but timers and
     interprocessor interrupts can occur on other CPUs. Interrupt frequencies
     can be useful in identifying misconfigured devices or areas of improvement
     in interrupt load, and can serve as a proxy for identifying device activity
     across the sample interval. For example, during a network-heavy workload,
     an increase in interrupts associated with Airport wireless ("ARPT"), or
     wired ethernet ("ETH0" "ETH1" etc.) is not unexpected. However, if the
     interrupt frequency for a given device is non-zero when the device is not
     active (e.g. if "HDAU" interrupts, for High Definition Audio, occur even
     when no audio is playing), that may be a driver error. The int_sources
     sampler attributes interrupts to the responsible InterruptEventSources,
     which helps disambiguate the cause of an interrupt if the vector serves
     more than one source.

     Battery Statistics

     The battery sampler reports battery discharge rates, current and maximum
     charge levels, cycle counts and degradation from design capacity across the
     interval in question, if a delta was reported by the battery management
     unit. Note that the battery controller data may arrive out-of-phase with
     respect to powermetrics samples, which can cause aliasing issues across
     short sample intervals. Discharge rates across discontinuities such as
     sleep/wake may also be inaccurate on some systems; however, the rate of
     change of the total charge level across longer intervals is a useful
     indicator of total system load. Powermetrics does not filter discharge
     rates for A/C connect/disconnect events, system sleep residency etc.
     Battery discharge rates are typically not comparable across machine models.

     Processor Energy Usage

     The cpu_power sampler reports data derived from the Intel energy models; as
     of the Sandy Bridge intel microarchitecture, the Intel power control unit
     internally maintains an energy consumption model whose details are
     proprietary, but are likely based on duty cycles for individual execution
     units, current voltage/frequency etc. These numbers are not strictly
     accurate but are correlated with actual energy consumption. This section
     lists: power dissipated by the processor package which includes the CPU
     cores, the integrated GPU and the system agent (integrated memory
     controller, last level cache), and separately, CPU core power and GT
     (integrated GPU) power (the latter two in a forthcoming version). The
     energy model data is generally not comparable across machine models.

     The cpu_power sampler next reports, on processors with Nehalem and newer
     microarchitectures, hardware derived processor frequency and idle residency
     information, labeled "P-states" and "C-states" respectively in Intel

     C-states are further classified in to "package c-states" and per-core C-
     states. The processor enters a "c-state" in the scheduler's idle loop,
     which results in clock-gating or power-gating CPU core and, potentially,
     package logic, considerably reducing power dissipation. High package c-
     state residency is a goal to strive for, as energy consumption of the CPU
     complex, integrated memory controller if any and DRAM is significantly
     reduced when in a package c-state. Package c-states occur when all CPU
     cores within the package are idle, and the on-die integrated GPU if any
     (SandyBridge mobile and beyond), on the system is also idle. Powermetrics
     reports package c-state residency as a fraction of the time sampled. This
     is available on Nehalem microarchitecture and newer processors. Note that
     some systems, such as Mac Pros, do not enable "package" c-states.

     Powermetrics also reports per-core c-state residencies, signifying when the
     core in question (which can include multiple SMTs or "hyperthreads") is
     idle, as well as active/inactive duty cycle histograms for each logical
     processor within the core. This is available on Nehalem microarchitecture
     and newer processors.

     This section also lists the average clock frequency at which the given
     logical processor executed when not idle within the sampled interval,
     expressed as both an absolute frequency in MHz and as a percentage of the
     nominal rated frequency. These average frequencies can vary due to the
     operating system's demand based dynamic voltage and frequency scaling. Some
     systems can execute at frequencies greater than the nominal or "P1"
     frequency, which is termed "turbo mode" on Intel systems. Such operation
     will manifest as > 100% of nominal frequency. Lengthy execution in turbo
     mode is typically energy inefficient, as those frequencies have high
     voltage requirements, resulting in a correspondingly quadratic increase in
     power insufficient to outweigh the reduction in execution time. Current
     systems typically have a single voltage/frequency domain per-package, but
     as the processors can execute out-of-phase, they may display different
     average execution frequencies.

     Disk Usage and Network Activity

     The network and disk samplers reports deltas in disk and network activity
     that occured during the sample. Also specifying --show-process-netstats and
     --show-process-io will give you this information on a per process basis in
     the tasks sampler.

     Backlight level

     The battery sampler also reports the instantaneous value of the backlight
     luminosity level. This value is likely not comparable across systems and
     machine models, but can be useful when comparing scenarios on a given


     The devices sampler, for each device, reports the time spent in each of the
     device's states over the course of the sample. The meaning of the different
     states is specific to each device. Powermetrics denotes low power states
     with an "L", device usable states with a "U" and power on states with an


     The smc sampler displays information supplied by the System Management
     Controller. On supported platforms, this includes fan speed and information
     from various temperature sensors. These are instantaneous values taken at
     the end of the sample window, and do not necessarily reflect the values at
     other times in the window.


     The thermal sampler displays the current thermal pressure the system is
     under. This is an instantaneous value taken at the end of the sample
     window, and does not necessarily reflect the value at other times in the


     The sfi sampler shows system wide selective forced idle statistics.
     Selective forced idle is a mechanism the operating system uses to limit
     system power while minimizing user impact, by throttling certain threads on
     the system. Each thread belongs to an SFI class, and this sampler displays
     how much each SFI class is currently being throttled. These are
     instantaneous values taken at the end of the sample window, and do not
     necessarily reflect the values at other times in the window. To get SFI
     wait time statistics on a per process basis use --show-process-wait-times.

     Changes in system time and sleep/wake can cause minor inaccuracies in
     reported cpu time.

Darwin                               5/1/12                               Darwin