# perf-stat

## NAME



           perf-stat - Run a command and gather performance counter
           statistics
    


## SYNOPSIS



           _perf stat_ [-e <EVENT> | --event=EVENT] [-a] <command>
           _perf stat_ [-e <EVENT> | --event=EVENT] [-a] -- <command> [<options>]
           _perf stat_ [-e <EVENT> | --event=EVENT] [-a] record [-o file] -- <command> [<options>]
           _perf stat_ report [-i file]
    


## DESCRIPTION



           This command runs a command and gathers performance counter
           statistics from it.
    


## OPTIONS



           <command>...
               Any command you can specify in a shell.
    
           record
               See STAT RECORD.
    
           report
               See STAT REPORT.
    
           -e, --event=
               Select the PMU event. Selection can be:
    
               •   a symbolic event name (use _perf list_ to list all events)
    
               •   a raw PMU event in the form of rN where N is a hexadecimal
                   value that represents the raw register encoding with the
                   layout of the event control registers as described by
                   entries in /sys/bus/event_source/devices/cpu/format/*.
    
               •   a symbolic or raw PMU event followed by an optional colon
                   and a list of event modifiers, e.g., cpu-cycles:p. See the
                   perf-list(1) man page for details on event modifiers.
    
               •   a symbolically formed event like _pmu/param1=0x3,param2/_
                   where param1 and param2 are defined as formats for the PMU
                   in /sys/bus/event_source/devices/<pmu>/format/*
    
                       'percore' is a event qualifier that sums up the event counts for both
                       hardware threads in a core. For example:
                       perf stat -A -a -e cpu/event,percore=1/,otherevent ...
    
               •   a symbolically formed event like
                   _pmu/config=M,config1=N,config2=K/_ where M, N, K are
                   numbers (in decimal, hex, octal format). Acceptable values
                   for each of _config_ , _config1_ and _config2_ parameters are
                   defined by corresponding entries in
                   /sys/bus/event_source/devices/<pmu>/format/*
    
                       Note that the last two syntaxes support prefix and glob matching in
                       the PMU name to simplify creation of events across multiple instances
                       of the same type of PMU in large systems (e.g. memory controller PMUs).
                       Multiple PMU instances are typical for uncore PMUs, so the prefix
                       'uncore_' is also ignored when performing this match.
    
           -i, --no-inherit
               child tasks do not inherit counters
    
           -p, --pid=<pid>
               stat events on existing process id (comma separated list)
    
           -t, --tid=<tid>
               stat events on existing thread id (comma separated list)
    
           -b, --bpf-prog
               stat events on existing bpf program id (comma separated list),
               requiring root rights. bpftool-prog could be used to find
               program id all bpf programs in the system. For example:
    
                   # bpftool prog | head -n 1
                   17247: tracepoint  name sys_enter  tag 192d548b9d754067  gpl
    
                   # perf stat -e cycles,instructions --bpf-prog 17247 --timeout 1000
    
                   Performance counter stats for 'BPF program(s) 17247':
    
                   85,967      cycles
                   28,982      instructions              #    0.34  insn per cycle
    
                   1.102235068 seconds time elapsed
    
           --bpf-counters
               Use BPF programs to aggregate readings from perf_events. This
               allows multiple perf-stat sessions that are counting the same
               metric (cycles, instructions, etc.) to share hardware
               counters. To use BPF programs on common events by default, use
               "perf config stat.bpf-counter-events=<list_of_events>".
    
           --bpf-attr-map
               With option "--bpf-counters", different perf-stat sessions
               share information about shared BPF programs and maps via a
               pinned hashmap. Use "--bpf-attr-map" to specify the path of
               this pinned hashmap. The default path is
               /sys/fs/bpf/perf_attr_map.
    
           -a, --all-cpus
               system-wide collection from all CPUs (default if no target is
               specified)
    
           --no-scale
               Don’t scale/normalize counter values
    
           -d, --detailed
               print more detailed statistics, can be specified up to 3 times
    
                         -d:          detailed events, L1 and LLC data cache
                      -d -d:     more detailed events, dTLB and iTLB events
                   -d -d -d:     very detailed events, adding prefetch events
    
           -r, --repeat=<n>
               repeat command and print average + stddev (max: 100). 0 means
               forever.
    
           -B, --big-num
               print large numbers with thousands' separators according to
               locale. Enabled by default. Use "--no-big-num" to disable.
               Default setting can be changed with "perf config
               stat.big-num=false".
    
           -C, --cpu=
               Count only on the list of CPUs provided. Multiple CPUs can be
               provided as a comma-separated list with no space: 0,1. Ranges
               of CPUs are specified with -: 0-2. In per-thread mode, this
               option is ignored. The -a option is still necessary to
               activate system-wide monitoring. Default is to count on all
               CPUs.
    
           -A, --no-aggr
               Do not aggregate counts across all monitored CPUs.
    
           -n, --null
               null run - Don’t start any counters.
    
           This can be useful to measure just elapsed wall-clock time - or to
           assess the raw overhead of perf stat itself, without running any
           counters.
    
           -v, --verbose
               be more verbose (show counter open errors, etc)
    
           -x SEP, --field-separator SEP
               print counts using a CSV-style output to make it easy to
               import directly into spreadsheets. Columns are separated by
               the string specified in SEP.
    
           --table
               Display time for each run (-r option), in a table format,
               e.g.:
    
                   $ perf stat --null -r 5 --table perf bench sched pipe
    
                   Performance counter stats for 'perf bench sched pipe' (5 runs):
    
                   # Table of individual measurements:
                   5.189 (-0.293) #
                   5.189 (-0.294) #
                   5.186 (-0.296) #
                   5.663 (+0.181) ##
                   6.186 (+0.703) ####
    
                   # Final result:
                   5.483 +- 0.198 seconds time elapsed  ( +-  3.62% )
    
           -G name, --cgroup name
               monitor only in the container (cgroup) called "name". This
               option is available only in per-cpu mode. The cgroup
               filesystem must be mounted. All threads belonging to container
               "name" are monitored when they run on the monitored CPUs.
               Multiple cgroups can be provided. Each cgroup is applied to
               the corresponding event, i.e., first cgroup to first event,
               second cgroup to second event and so on. It is possible to
               provide an empty cgroup (monitor all the time) using, e.g., -G
               foo,,bar. Cgroups must have corresponding events, i.e., they
               always refer to events defined earlier on the command line. If
               the user wants to track multiple events for a specific cgroup,
               the user can use _-e e1 -e e2 -G foo,foo_ or just use _-e e1 -e_
               _e2 -G foo_.
    
           If wanting to monitor, say, _cycles_ for a cgroup and also for
           system wide, this command line can be used: _perf stat -e cycles -G_
           _cgroup_name -a -e cycles_.
    
           --for-each-cgroup name
               Expand event list for each cgroup in "name" (allow multiple
               cgroups separated by comma). It also support regex patterns to
               match multiple groups. This has same effect that repeating -e
               option and -G option for each event x name. This option cannot
               be used with -G/--cgroup option.
    
           -o file, --output file
               Print the output into the designated file.
    
           --append
               Append to the output file designated with the -o option.
               Ignored if -o is not specified.
    
           --log-fd
               Log output to fd, instead of stderr. Complementary to
               --output, and mutually exclusive with it. --append may be used
               here. Examples: 3>results perf stat --log-fd 3 -- $cmd
               3>>results perf stat --log-fd 3 --append -- $cmd
    
           --control=fifo:ctl-fifo[,ack-fifo], --control=fd:ctl-fd[,ack-fd]
               ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd as
               follows. Listen on ctl-fd descriptor for command to control
               measurement (_enable_ : enable events, _disable_ : disable events).
               Measurements can be started with events disabled using
               --delay=-1 option. Optionally send control command completion
               (_ack\n_) to ack-fd descriptor to synchronize with the
               controlling process. Example of bash shell script to enable
               and disable events during measurements:
    
                   #!/bin/bash
    
                   ctl_dir=/tmp/
    
                   ctl_fifo=${ctl_dir}perf_ctl.fifo
                   test -p ${ctl_fifo} && unlink ${ctl_fifo}
                   mkfifo ${ctl_fifo}
                   exec {ctl_fd}<>${ctl_fifo}
    
                   ctl_ack_fifo=${ctl_dir}perf_ctl_ack.fifo
                   test -p ${ctl_ack_fifo} && unlink ${ctl_ack_fifo}
                   mkfifo ${ctl_ack_fifo}
                   exec {ctl_fd_ack}<>${ctl_ack_fifo}
    
                   perf stat -D -1 -e cpu-cycles -a -I 1000       \
                             --control fd:${ctl_fd},${ctl_fd_ack} \
                             \-- sleep 30 &
                   perf_pid=$!
    
                   sleep 5  && echo 'enable' >&${ctl_fd} && read -u ${ctl_fd_ack} e1 && echo "enabled(${e1})"
                   sleep 10 && echo 'disable' >&${ctl_fd} && read -u ${ctl_fd_ack} d1 && echo "disabled(${d1})"
    
                   exec {ctl_fd_ack}>&-
                   unlink ${ctl_ack_fifo}
    
                   exec {ctl_fd}>&-
                   unlink ${ctl_fifo}
    
                   wait -n ${perf_pid}
                   exit $?
    
           --pre, --post
               Pre and post measurement hooks, e.g.:
    
           perf stat --repeat 10 --null --sync --pre _make -s_
           _O=defconfig-build/clean_ -- make -s -j64 O=defconfig-build/ bzImage
    
           -I msecs, --interval-print msecs
               Print count deltas every N milliseconds (minimum: 1ms) The
               overhead percentage could be high in some cases, for instance
               with small, sub 100ms intervals. Use with caution. example:
               _perf stat -I 1000 -e cycles -a sleep 5_
    
           If the metric exists, it is calculated by the counts generated in
           this interval and the metric is printed after #.
    
           --interval-count times
               Print count deltas for fixed number of times. This option
               should be used together with "-I" option. example: _perf stat_
               _-I 1000 --interval-count 2 -e cycles -a_
    
           --interval-clear
               Clear the screen before next interval.
    
           --timeout msecs
               Stop the _perf stat_ session and print count deltas after N
               milliseconds (minimum: 10 ms). This option is not supported
               with the "-I" option. example: _perf stat --time 2000 -e cycles_
               _-a_
    
           --metric-only
               Only print computed metrics. Print them in a single line.
               Don’t show any raw values. Not supported with --per-thread.
    
           --per-socket
               Aggregate counts per processor socket for system-wide mode
               measurements. This is a useful mode to detect imbalance
               between sockets. To enable this mode, use --per-socket in
               addition to -a. (system-wide). The output includes the socket
               number and the number of online processors on that socket.
               This is useful to gauge the amount of aggregation.
    
           --per-die
               Aggregate counts per processor die for system-wide mode
               measurements. This is a useful mode to detect imbalance
               between dies. To enable this mode, use --per-die in addition
               to -a. (system-wide). The output includes the die number and
               the number of online processors on that die. This is useful to
               gauge the amount of aggregation.
    
           --per-cluster
               Aggregate counts per processor cluster for system-wide mode
               measurement. This is a useful mode to detect imbalance between
               clusters. To enable this mode, use --per-cluster in addition
               to -a. (system-wide). The output includes the cluster number
               and the number of online processors on that cluster. This is
               useful to gauge the amount of aggregation. The information of
               cluster ID and related CPUs can be gotten from
               /sys/devices/system/cpu/cpuX/topology/cluster_{id, cpus}.
    
           --per-cache
               Aggregate counts per cache instance for system-wide mode
               measurements. By default, the aggregation happens for the
               cache level at the highest index in the system. To specify a
               particular level, mention the cache level alongside the option
               in the format [Ll][1-9][0-9]*. For example: Using option
               "--per-cache=l3" or "--per-cache=L3" will aggregate the
               information at the boundary of the level 3 cache in the
               system.
    
           --per-core
               Aggregate counts per physical processor for system-wide mode
               measurements. This is a useful mode to detect imbalance
               between physical cores. To enable this mode, use --per-core in
               addition to -a. (system-wide). The output includes the core
               number and the number of online logical processors on that
               physical processor.
    
           --per-thread
               Aggregate counts per monitored threads, when monitoring
               threads (-t option) or processes (-p option).
    
           --per-node
               Aggregate counts per NUMA nodes for system-wide mode
               measurements. This is a useful mode to detect imbalance
               between NUMA nodes. To enable this mode, use --per-node in
               addition to -a. (system-wide).
    
           -D msecs, --delay msecs
               After starting the program, wait msecs before measuring (-1:
               start with events disabled). This is useful to filter out the
               startup phase of the program, which is often very different.
    
           -T, --transaction
               Print statistics of transactional execution if supported.
    
           --metric-no-group
               By default, events to compute a metric are placed in weak
               groups. The group tries to enforce scheduling all or none of
               the events. The --metric-no-group option places events outside
               of groups and may increase the chance of the event being
               scheduled - leading to more accuracy. However, as events may
               not be scheduled together accuracy for metrics like
               instructions per cycle can be lower - as both metrics may no
               longer be being measured at the same time.
    
           --metric-no-merge
               By default metric events in different weak groups can be
               shared if one group contains all the events needed by another.
               In such cases one group will be eliminated reducing event
               multiplexing and making it so that certain groups of metrics
               sum to 100%. A downside to sharing a group is that the group
               may require multiplexing and so accuracy for a small group
               that need not have multiplexing is lowered. This option
               forbids the event merging logic from sharing events between
               groups and may be used to increase accuracy in this case.
    
           --metric-no-threshold
               Metric thresholds may increase the number of events necessary
               to compute whether a metric has exceeded its threshold
               expression. This may not be desirable, for example, as the
               events can introduce multiplexing. This option disables the
               adding of threshold expression events for a metric. However,
               if there are sufficient events to compute the threshold then
               the threshold is still computed and used to color the metric’s
               computed value.
    
           --quiet
               Don’t print output, warnings or messages. This is useful with
               perf stat record below to only write data to the perf.data
               file.
    


## STAT RECORD



           Stores stat data into perf data file.
    
           -o file, --output file
               Output file name.
    


## STAT REPORT



           Reads and reports stat data from perf data file.
    
           -i file, --input file
               Input file name.
    
           --per-socket
               Aggregate counts per processor socket for system-wide mode
               measurements.
    
           --per-die
               Aggregate counts per processor die for system-wide mode
               measurements.
    
           --per-cluster
               Aggregate counts perf processor cluster for system-wide mode
               measurements.
    
           --per-cache
               Aggregate counts per cache instance for system-wide mode
               measurements. By default, the aggregation happens for the
               cache level at the highest index in the system. To specify a
               particular level, mention the cache level alongside the option
               in the format [Ll][1-9][0-9]*. For example: Using option
               "--per-cache=l3" or "--per-cache=L3" will aggregate the
               information at the boundary of the level 3 cache in the
               system.
    
           --per-core
               Aggregate counts per physical processor for system-wide mode
               measurements.
    
           -M, --metrics
               Print metrics or metricgroups specified in a comma separated
               list. For a group all metrics from the group are added. The
               events from the metrics are automatically measured. See perf
               list output for the possible metrics and metricgroups.
    
                   When threshold information is available for a metric, the
                   color red is used to signify a metric has exceeded a threshold
                   while green shows it hasn't. The default color means that
                   no threshold information was available or the threshold
                   couldn't be computed.
    
           -A, --no-aggr, --no-merge
               Do not aggregate/merge counts across monitored CPUs or PMUs.
    
           When multiple events are created from a single event
           specification, stat will, by default, aggregate the event counts
           and show the result in a single row. This option disables that
           behavior and shows the individual events and counts.
    
           Multiple events are created from a single event specification
           when:
    
            1. PID monitoring isn’t requested and the system has more than
               one CPU. For example, a system with 8 SMT threads will have
               one event opened on each thread and aggregation is performed
               across them.
    
            2. Prefix or glob wildcard matching is used for the PMU name. For
               example, multiple memory controller PMUs may exist typically
               with a suffix of _0, _1, etc. By default the event counts will
               all be combined if the PMU is specified without the suffix
               such as uncore_imc rather than uncore_imc_0.
    
            3. Aliases, which are listed immediately after the Kernel PMU
               events by perf list, are used.
    
               --hybrid-merge
                   Merge core event counts from all core PMUs. In hybrid or
                   big.LITTLE systems by default each core PMU will report
                   its count separately. This option forces core PMU counts
                   to be combined to give a behavior closer to having a
                   single CPU type in the system.
    
               --topdown
                   Print top-down metrics supported by the CPU. This allows
                   to determine bottle necks in the CPU pipeline for CPU
                   bound workloads, by breaking the cycles consumed down into
                   frontend bound, backend bound, bad speculation and
                   retiring.
    
           Frontend bound means that the CPU cannot fetch and decode
           instructions fast enough. Backend bound means that computation or
           memory access is the bottle neck. Bad Speculation means that the
           CPU wasted cycles due to branch mispredictions and similar issues.
           Retiring means that the CPU computed without an apparently
           bottleneck. The bottleneck is only the real bottleneck if the
           workload is actually bound by the CPU and not by something else.
    
           For best results it is usually a good idea to use it with interval
           mode like -I 1000, as the bottleneck of workloads can change
           often.
    
           This enables --metric-only, unless overridden with
           --no-metric-only.
    
           The following restrictions only apply to older Intel CPUs and
           Atom, on newer CPUs (IceLake and later) TopDown can be collected
           for any thread:
    
           The top down metrics are collected per core instead of per CPU
           thread. Per core mode is automatically enabled and -a (global
           monitoring) is needed, requiring root rights or
           perf.perf_event_paranoid=-1.
    
           Topdown uses the full Performance Monitoring Unit, and needs
           disabling of the NMI watchdog (as root): echo 0 >
           /proc/sys/kernel/nmi_watchdog for best results. Otherwise the
           bottlenecks may be inconsistent on workload with changing phases.
    
           To interpret the results it is usually needed to know on which
           CPUs the workload runs on. If needed the CPUs can be forced using
           taskset.
    
           --record-tpebs
               Enable automatic sampling on Intel TPEBS retire_latency events
               (event with :R modifier). Without this option, perf would not
               capture dynamic retire_latency at runtime. Currently, a zero
               value is assigned to the retire_latency event when this option
               is not set. The TPEBS hardware feature starts from Intel
               Granite Rapids microarchitecture. This option only exists in
               X86_64 and is meaningful on Intel platforms with TPEBS
               feature.
    
           --tpebs-mode=[mean|min|max|last]
               Set how retirement latency events have their sample times
               combined. The default "mean" gives the average of retirement
               latency. "min" or "max" give the smallest or largest retirment
               latency times respectively. "last" uses the last retirment
               latency sample’s time.
    
           --td-level
               Print the top-down statistics that equal the input level. It
               allows users to print the interested top-down metrics level
               instead of the level 1 top-down metrics.
    
           As the higher levels gather more metrics and use more counters
           they will be less accurate. By convention a metric can be examined
           by appending __group_ to it and this will increase accuracy compared
           to gathering all metrics for a level. For example, level 1
           analysis may highlight _tma_frontend_bound_. This metric may be
           drilled into with _tma_frontend_bound_group_ with _perf stat -M_
           _tma_frontend_bound_group..._.
    
           Error out if the input is higher than the supported max level.
    
           --smi-cost
               Measure SMI cost if msr/aperf/ and msr/smi/ events are
               supported.
    
           During the measurement, the /sys/device/cpu/freeze_on_smi will be
           set to freeze core counters on SMI. The aperf counter will not be
           effected by the setting. The cost of SMI can be measured by (aperf
           - unhalted core cycles).
    
           In practice, the percentages of SMI cycles is very useful for
           performance oriented analysis. --metric_only will be applied by
           default. The output is SMI cycles%, equals to (aperf - unhalted
           core cycles) / aperf
    
           Users who wants to get the actual value can apply
           --no-metric-only.
    
           --all-kernel
               Configure all used events to run in kernel space.
    
           --all-user
               Configure all used events to run in user space.
    
           --percore-show-thread
               The event modifier "percore" has supported to sum up the event
               counts for all hardware threads in a core and show the counts
               per core.
    
           This option with event modifier "percore" enabled also sums up the
           event counts for all hardware threads in a core but show the sum
           counts per hardware thread. This is essentially a replacement for
           the any bit and convenient for post processing.
    
           --summary
               Print summary for interval mode (-I).
    
           --no-csv-summary
               Don’t print _summary_ at the first column for CVS summary
               output. This option must be used with -x and --summary.
    
           This option can be enabled in perf config by setting the variable
           _stat.no-csv-summary_.
    
           $ perf config stat.no-csv-summary=true
    
           --cputype
               Only enable events on applying cpu with this type for hybrid
               platform (e.g. core or atom)"
    


## EXAMPLES



           $ perf stat -- make
    
               Performance counter stats for 'make':
    
                  83723.452481      task-clock:u (msec)       #    1.004 CPUs utilized
                             0      context-switches:u        #    0.000 K/sec
                             0      cpu-migrations:u          #    0.000 K/sec
                     3,228,188      page-faults:u             #    0.039 M/sec
               229,570,665,834      cycles:u                  #    2.742 GHz
               313,163,853,778      instructions:u            #    1.36  insn per cycle
                69,704,684,856      branches:u                #  832.559 M/sec
                 2,078,861,393      branch-misses:u           #    2.98% of all branches
    
               83.409183620 seconds time elapsed
    
               74.684747000 seconds user
                8.739217000 seconds sys
    


## TIMINGS



           As displayed in the example above we can display 3 types of
           timings. We always display the time the counters were
           enabled/alive:
    
               83.409183620 seconds time elapsed
    
           For workload sessions we also display time the workloads spent in
           user/system lands:
    
               74.684747000 seconds user
                8.739217000 seconds sys
    
           Those times are the very same as displayed by the _time_ tool.
    


## CSV FORMAT



           With -x, perf stat is able to output a not-quite-CSV format output
           Commas in the output are not put into "". To make it easy to parse
           it is recommended to use a different character like -x \;
    
           The fields are in this order:
    
           •   optional usec time stamp in fractions of second (with -I xxx)
    
           •   optional CPU, core, or socket identifier
    
           •   optional number of logical CPUs aggregated
    
           •   counter value
    
           •   unit of the counter value or empty
    
           •   event name
    
           •   run time of counter
    
           •   percentage of measurement time the counter was running
    
           •   optional variance if multiple values are collected with -r
    
           •   optional metric value
    
           •   optional unit of metric
    
           Additional metrics may be printed with all earlier fields being
           empty.
    


## INTEL HYBRID SUPPORT



           Support for Intel hybrid events within perf tools.
    
           For some Intel platforms, such as AlderLake, which is hybrid
           platform and it consists of atom cpu and core cpu. Each cpu has
           dedicated event list. Part of events are available on core cpu,
           part of events are available on atom cpu and even part of events
           are available on both.
    
           Kernel exports two new cpu pmus via sysfs:
           /sys/bus/event_source/devices/cpu_core
           /sys/bus/event_source/devices/cpu_atom
    
           The _cpus_ files are created under the directories. For example,
    
           cat /sys/bus/event_source/devices/cpu_core/cpus 0-15
    
           cat /sys/bus/event_source/devices/cpu_atom/cpus 16-23
    
           It indicates cpu0-cpu15 are core cpus and cpu16-cpu23 are atom
           cpus.
    
           As before, use perf-list to list the symbolic event.
    
           perf list
    
           inst_retired.any [Fixed Counter: Counts the number of instructions
           retired. Unit: cpu_atom] inst_retired.any [Number of instructions
           retired. Fixed Counter - architectural event. Unit: cpu_core]
    
           The _Unit: xxx_ is added to brief description to indicate which pmu
           the event is belong to. Same event name but with different pmu can
           be supported.
    
           Enable hybrid event with a specific pmu
    
           To enable a core only event or atom only event, following syntax
           is supported:
    
                       cpu_core/<event name>/
               or
                       cpu_atom/<event name>/
    
           For example, count the _cycles_ event on core cpus.
    
               perf stat -e cpu_core/cycles/
    
           Create two events for one hardware event automatically
    
           When creating one event and the event is available on both atom
           and core, two events are created automatically. One is for atom,
           the other is for core. Most of hardware events and cache events
           are available on both cpu_core and cpu_atom.
    
           For hardware events, they have pre-defined configs (e.g. 0 for
           cycles). But on hybrid platform, kernel needs to know where the
           event comes from (from atom or from core). The original perf event
           type PERF_TYPE_HARDWARE can’t carry pmu information. So now this
           type is extended to be PMU aware type. The PMU type ID is stored
           at attr.config[63:32].
    
           PMU type ID is retrieved from sysfs.
           /sys/bus/event_source/devices/cpu_atom/type
           /sys/bus/event_source/devices/cpu_core/type
    
           The new attr.config layout for PERF_TYPE_HARDWARE:
    
           PERF_TYPE_HARDWARE: 0xEEEEEEEE000000AA AA: hardware event ID
           EEEEEEEE: PMU type ID
    
           Cache event is similar. The type PERF_TYPE_HW_CACHE is extended to
           be PMU aware type. The PMU type ID is stored at
           attr.config[63:32].
    
           The new attr.config layout for PERF_TYPE_HW_CACHE:
    
           PERF_TYPE_HW_CACHE: 0xEEEEEEEE00DDCCBB BB: hardware cache ID CC:
           hardware cache op ID DD: hardware cache op result ID EEEEEEEE: PMU
           type ID
    
           When enabling a hardware event without specified pmu, such as,
           perf stat -e cycles -a (use system-wide in this example), two
           events are created automatically.
    
               ------------------------------------------------------------
               perf_event_attr:
                 size                             120
                 config                           0x400000000
                 sample_type                      IDENTIFIER
                 read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
                 disabled                         1
                 inherit                          1
                 exclude_guest                    1
               ------------------------------------------------------------
    
           and
    
               ------------------------------------------------------------
               perf_event_attr:
                 size                             120
                 config                           0x800000000
                 sample_type                      IDENTIFIER
                 read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
                 disabled                         1
                 inherit                          1
                 exclude_guest                    1
               ------------------------------------------------------------
    
           type 0 is PERF_TYPE_HARDWARE. 0x4 in 0x400000000 indicates it’s
           cpu_core pmu. 0x8 in 0x800000000 indicates it’s cpu_atom pmu (atom
           pmu type id is random).
    
           The kernel creates _cycles_ (0x400000000) on cpu0-cpu15 (core cpus),
           and create _cycles_ (0x800000000) on cpu16-cpu23 (atom cpus).
    
           For perf-stat result, it displays two events:
    
               Performance counter stats for 'system wide':
    
               6,744,979      cpu_core/cycles/
               1,965,552      cpu_atom/cycles/
    
           The first _cycles_ is core event, the second _cycles_ is atom event.
    
           Thread mode example:
    
           perf-stat reports the scaled counts for hybrid event and with a
           percentage displayed. The percentage is the event’s running
           time/enabling time.
    
           One example, _triad_loop_ runs on cpu16 (atom core), while we can
           see the scaled value for core cycles is 160,444,092 and the
           percentage is 0.47%.
    
           perf stat -e cycles -- taskset -c 16 ./triad_loop
    
           As previous, two events are created.
    
               .ft C
               perf_event_attr:
                 size                             120
                 config                           0x400000000
                 sample_type                      IDENTIFIER
                 read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
                 disabled                         1
                 inherit                          1
                 enable_on_exec                   1
                 exclude_guest                    1
               .ft
    
           and
    
               .ft C
               perf_event_attr:
                 size                             120
                 config                           0x800000000
                 sample_type                      IDENTIFIER
                 read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
                 disabled                         1
                 inherit                          1
                 enable_on_exec                   1
                 exclude_guest                    1
               .ft
    
               Performance counter stats for 'taskset -c 16 ./triad_loop':
    
               233,066,666      cpu_core/cycles/                                              (0.43%)
               604,097,080      cpu_atom/cycles/                                              (99.57%)
    
           perf-record:
    
           If there is no _-e_ specified in perf record, on hybrid platform, it
           creates two default _cycles_ and adds them to event list. One is for
           core, the other is for atom.
    
           perf-stat:
    
           If there is no _-e_ specified in perf stat, on hybrid platform,
           besides of software events, following events are created and added
           to event list in order.
    
           cpu_core/cycles/, cpu_atom/cycles/, cpu_core/instructions/,
           cpu_atom/instructions/, cpu_core/branches/, cpu_atom/branches/,
           cpu_core/branch-misses/, cpu_atom/branch-misses/
    
           Of course, both perf-stat and perf-record support to enable hybrid
           event with a specific pmu.
    
           e.g. perf stat -e cpu_core/cycles/ perf stat -e cpu_atom/cycles/
           perf stat -e cpu_core/r1a/ perf stat -e cpu_atom/L1-icache-loads/
           perf stat -e cpu_core/cycles/,cpu_atom/instructions/ perf stat -e
           _{cpu_core/cycles/,cpu_core/instructions/}_
    
           But _{cpu_core/cycles/,cpu_atom/instructions/}_ will return warning
           and disable grouping, because the pmus in group are not matched
           (cpu_core vs. cpu_atom).
    


## JSON FORMAT



           With -j, perf stat is able to print out a JSON format output that
           can be used for parsing.
    
           •   interval : optional timestamp in fractions of second (with -I)
    
           •   optional aggregate options:
    
           •   core : core identifier (with --per-core)
    
           •   die : die identifier (with --per-die)
    
           •   socket : socket identifier (with --per-socket)
    
           •   node : node identifier (with --per-node)
    
           •   thread : thread identifier (with --per-thread)
    
           •   counters : number of aggregated PMU counters
    
           •   counter-value : counter value
    
           •   unit : unit of the counter value or empty
    
           •   event : event name
    
           •   variance : optional variance if multiple values are collected
               (with -r)
    
           •   event-runtime : run time of the event
    
           •   pcnt-running : percentage of time the event was running
    
           •   metric-value : optional metric value
    
           •   metric-unit : optional unit of metric
    


* * *