PERF-STAT(1)

PERF-STAT(1) — from the perf Manual

---

💖 NAME 💖

perf-stat — Run a command and gather performance counter statistics. That's it, that's the whole iconic behavior. 💅

🦋 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 🌸

Okay bestie, the tea is simple: this command runs a command and gathers performance counter statistics from it. Literally main character energy for your CPU. 🔥

✨ OPTIONS ✨

• <command>... — any command you can specify in a shell. 🫶
• record — see STAT RECORD. iykyk.
• 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/*
  • 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/*

Also, 'percore' is an 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 ...

Ngl this next bit is important: 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. periodt.
• -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. 🗺️
• --pfm-events events — select a PMU event using libpfm4 syntax (see http://perfmon2.sf.net) including support for event filters. For example --pfm-events inst_retired:any_p:u:c=1:i. More than one event can be passed to the option using the comma separator. Hardware events and generic hardware events cannot be mixed together. The latter must be used with the -e option. The -e option and this one can be mixed and matched. Events can be grouped using the {} notation. ✨
• -a, --all-cpus — system-wide collection from all CPUs (default if no target is specified). 🌈
• --no-scale — don't scale/normalize counter values. no cap, leave the numbers alone.
• -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. 😭 forever is a long time, bestie.
• -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. 💰 slay those separators.
• -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. fr fr, keep them separate. ✋
• -n, --null — null run — don't start any counters. vibe check: zero counters, zero drama.

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. 🕰️

• --hide-zero-events — do not show events with a zero count. bye zeros 👋
• -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. 📊 it's giving spreadsheet but make it performance.
• --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. ➕ not me forgetting that if -o isn't there, this gets ignored.
• --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 — stops the perf stat session and prints count deltas once msecs milliseconds have gone by (minimum is 10 ms, so don't get cute with it 💅). Heads up bestie: this one is not supported with the -I option. Example, so you can see it in the wild:

perf stat --time 2000 -e cycles -a

• --metric-only — prints only the computed metrics, all on a single line, and shows zero raw values. Ngl it's giving "just the vibes, no receipts" ✨. Not supported with --per-thread.
• --per-socket — aggregates counts per processor socket, for system-wide mode measurements. This is the mode you want when you're trying to spot imbalance between sockets 🫶. To turn it on, use --per-socket together with -a (system-wide, periodt). The output includes the socket number and the number of online processors on that socket — super useful for gauging how much aggregation actually happened.
• --per-die — aggregates counts per processor die, again for system-wide mode measurements. Great for catching imbalance between dies 💀. Enable it by using --per-die plus -a (system-wide). Output gives you the die number and the number of online processors on that die, so you can gauge the amount of aggregation.
• --per-cluster — aggregates counts per processor cluster, system-wide mode measurement style. Detects imbalance between clusters, iconic behavior. Use --per-cluster in addition to -a (system-wide) to enable. The output includes the cluster number and the number of online processors on that cluster — useful for gauging the amount of aggregation. You can get the cluster ID and its related CPUs from

/sys/devices/system/cpu/cpuX/topology/cluster_{id, cpus}

• --per-cache — aggregates 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 (main character cache, honestly). Wanna pick a specific level? Mention the cache level alongside the option in the format [Ll][1-9][0-9]*. For example: using the option --per-cache=l3 or --per-cache=L3 will aggregate the info at the boundary of the level 3 cache in the system 🌸.
• --per-core — aggregates counts per physical processor for system-wide mode measurements. Perfect for spotting imbalance between physical cores 🔥. Turn it on with --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 — aggregates counts per monitored thread, for when you're monitoring threads (the -t option) or processes (the -p option) 🧚.
• --per-node — aggregates counts per NUMA node for system-wide mode measurements. Detects imbalance between NUMA nodes, lowkey essential. Use --per-node in addition to -a (system-wide) to enable it.
• -D msecs, --delay msecs — after starting the program, wait msecs before measuring. Special value: -1 means start with events disabled 👀. This one's a lifesaver for filtering out the startup phase of the program, which is often very different from the rest.
• -T, --transaction — prints statistics of transactional execution if supported (keyword: if 😭).
• --metric-no-group — okay so by default, events that compute a metric get placed in weak groups, and the group tries to enforce scheduling all of the events or none of them. The --metric-no-group option puts events outside of groups, which may increase the chance of the event being scheduled — leading to more accuracy 🎀. Downside though: since events may not be scheduled together, accuracy for metrics like instructions per cycle can be lower, because both metrics may no longer be measured at the same time. Trade-offs, bestie.
• --metric-no-merge — by default, metric events in different weak groups can be shared if one group contains all the events needed by another. When that happens, one group gets eliminated — which reduces event multiplexing and makes it so certain groups of metrics sum to 100%. The downside of sharing a group is that the group may require multiplexing, so accuracy for a small group that need not have multiplexing gets lowered 💀. This option forbids the event merging logic from sharing events between groups, and may be used to increase accuracy in that case.
• --metric-no-threshold — metric thresholds may increase the number of events necessary to compute whether a metric has exceeded its threshold expression. That's not always desirable — for example, the events can introduce multiplexing 🙈. This option disables the adding of threshold expression events for a metric. But (and this part matters): if there are sufficient events to compute the threshold, then the threshold is still computed and still used to color the metric's computed value 🌈.
• --quiet — don't print output, warnings or messages. Ngl this one's a whole mood. It's useful with perf stat record (below) so you only write data to the perf.data file 🤫.
• --no-affinity — don't change scheduler CPU affinities when iterating over CPUs. This disables an optimization aimed at minimizing interprocessor interrupts ⭐.

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📁 STAT RECORD 📁

Stores stat data into a perf data file. Very "save it for later" of it 💾.

• -o file, --output file — output file name 🎀.

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STAT REPORT 💅

Okay so this is the part where perf stat actually reads your stat data file and reports it back to you. Iconic behavior honestly.

• -i file, --input file — the input file name, aka where your data lives. give it the file bestie 🫶
• --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 per 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. Wanna pick a specific 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. lowercase or uppercase, she does not care ✨
• --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. literally a vibe check for your metrics 🌈

• -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. no cap, every single one gets its own row 💅

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. bringing the girlies together 🫶
• --topdown — print top-down metrics supported by the CPU. This allows you to determine bottlenecks 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 bottleneck. Bad Speculation means that the CPU wasted cycles due to branch mispredictions and similar issues. Retiring means that the CPU computed without an apparent bottleneck. The bottleneck is only the real bottleneck if the workload is actually bound by the CPU and not by something else. read that twice bestie, it matters 😭

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. main character energy that never sits still honestly.

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) for best results. Otherwise the bottlenecks may be inconsistent on workload with changing phases.

echo 0 > /proc/sys/kernel/nmi_watchdog

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. very specific, very slay ⭐
• --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 retirement latency times respectively. "last" uses the last retirement latency sample's time. pick your fighter 💅
• --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. respectfully, know your limits 🙈

• --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. balance, bestie 🌸
• --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. it's giving spreadsheets but make it cute 💜

• --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)
• --pmu-filter — only enable events on applying pmu with specified for multiple pmus with same type (e.g. hisi_sicl2_cpa0 or hisi_sicl0_cpa0)

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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

look at all those numbers bestie, she ate 🔥

---

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. no cap, same numbers, different font 💅

---

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 \; — honestly a glow-up for your parser ngl.

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. ghost fields, iconic 🦋

🌈 INTEL HYBRID SUPPORT 🌈

Support for Intel hybrid events within perf tools. 💖

Okay so for some Intel platforms — AlderLake, for example — it’s a hybrid platform, and it consists of atom cpu and core cpu. Each cpu has a 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. iykyk ✨

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. the way that actually maps out so cleanly 🦋

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. periodt 💅

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). not me knowing the random atom pmu type id is just out here vibing 🙈

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. literally the duo we didn’t know we needed 💖

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.

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

and

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

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). fr fr do not ignore that warning bestie 💀

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✨ JSON FORMAT ✨

With -j, perf stat is able to print out a JSON format output that can be used for parsing. parsing girlies rise 🧚

• 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

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🌸 SEE ALSO 🌸

perf-top(1), perf-list(1) — go read those next, bestie, they’re iconic too 👑

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💖 aaaand that’s the page! Source/version: perf; date: 10/31/2026; manual page: PERF-STAT(1). bye bestie, go count some cycles! 💅✨