PERF-STAT(1) perf Manual PERF-STAT(1)
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-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-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.
--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.
• timestamp : optional usec time stamp 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)
• 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)
• runtime : run time of counter
• metric-value : optional metric value
• metric-unit : optional unit of metric
SEE ALSO
perf-top(1), perf-list(1)
perf 11/18/2025 PERF-STAT(1)
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