path: root/tools/perf/Documentation/perf-list.txt

perf-list(1)
============

NAME
----
perf-list - List all symbolic event types

SYNOPSIS
--------
[verse]
'perf list' [--no-desc] [--long-desc] [hw|sw|cache|tracepoint|pmu|event_glob]

DESCRIPTION
-----------
This command displays the symbolic event types which can be selected in the
various perf commands with the -e option.

OPTIONS
-------
--no-desc::
Don't print descriptions.

-v::
--long-desc::
Print longer event descriptions.


[[EVENT_MODIFIERS]]
EVENT MODIFIERS
---------------

Events can optionally have a modifier by appending a colon and one or
more modifiers. Modifiers allow the user to restrict the events to be
counted. The following modifiers exist:

 u - user-space counting
 k - kernel counting
 h - hypervisor counting
 I - non idle counting
 G - guest counting (in KVM guests)
 H - host counting (not in KVM guests)
 p - precise level
 P - use maximum detected precise level
 S - read sample value (PERF_SAMPLE_READ)
 D - pin the event to the PMU

The 'p' modifier can be used for specifying how precise the instruction
address should be. The 'p' modifier can be specified multiple times:

 0 - SAMPLE_IP can have arbitrary skid
 1 - SAMPLE_IP must have constant skid
 2 - SAMPLE_IP requested to have 0 skid
 3 - SAMPLE_IP must have 0 skid, or uses randomization to avoid
     sample shadowing effects.

For Intel systems precise event sampling is implemented with PEBS
which supports up to precise-level 2, and precise level 3 for
some special cases

On AMD systems it is implemented using IBS (up to precise-level 2).
The precise modifier works with event types 0x76 (cpu-cycles, CPU
clocks not halted) and 0xC1 (micro-ops retired). Both events map to
IBS execution sampling (IBS op) with the IBS Op Counter Control bit
(IbsOpCntCtl) set respectively (see AMD64 Architecture Programmer’s
Manual Volume 2: System Programming, 13.3 Instruction-Based
Sampling). Examples to use IBS:

 perf record -a -e cpu-cycles:p ...    # use ibs op counting cycles
 perf record -a -e r076:p ...          # same as -e cpu-cycles:p
 perf record -a -e r0C1:p ...          # use ibs op counting micro-ops

RAW HARDWARE EVENT DESCRIPTOR
-----------------------------
Even when an event is not available in a symbolic form within perf right now,
it can be encoded in a per processor specific way.

For instance For x86 CPUs NNN represents the raw register encoding with the
layout of IA32_PERFEVTSELx MSRs (see [Intel® 64 and IA-32 Architectures Software Developer's Manual Volume 3B: System Programming Guide] Figure 30-1 Layout
of IA32_PERFEVTSELx MSRs) or AMD's PerfEvtSeln (see [AMD64 Architecture Programmer’s Manual Volume 2: System Programming], Page 344,
Figure 13-7 Performance Event-Select Register (PerfEvtSeln)).

Note: Only the following bit fields can be set in x86 counter
registers: event, umask, edge, inv, cmask. Esp. guest/host only and
OS/user mode flags must be setup using <<EVENT_MODIFIERS, EVENT
MODIFIERS>>.

Example:

If the Intel docs for a QM720 Core i7 describe an event as:

  Event  Umask  Event Mask
  Num.   Value  Mnemonic    Description                        Comment

  A8H      01H  LSD.UOPS    Counts the number of micro-ops     Use cmask=1 and
                            delivered by loop stream detector  invert to count
                                                               cycles

raw encoding of 0x1A8 can be used:

 perf stat -e r1a8 -a sleep 1
 perf record -e r1a8 ...

You should refer to the processor specific documentation for getting these
details. Some of them are referenced in the SEE ALSO section below.

ARBITRARY PMUS
--------------

perf also supports an extended syntax for specifying raw parameters
to PMUs. Using this typically requires looking up the specific event
in the CPU vendor specific documentation.

The available PMUs and their raw parameters can be listed with

  ls /sys/devices/*/format

For example the raw event "LSD.UOPS" core pmu event above could
be specified as

  perf stat -e cpu/event=0xa8,umask=0x1,name=LSD.UOPS_CYCLES,cmask=1/ ...

PER SOCKET PMUS
---------------

Some PMUs are not associated with a core, but with a whole CPU socket.
Events on these PMUs generally cannot be sampled, but only counted globally
with perf stat -a. They can be bound to one logical CPU, but will measure
all the CPUs in the same socket.

This example measures memory bandwidth every second
on the first memory controller on socket 0 of a Intel Xeon system

  perf stat -C 0 -a uncore_imc_0/cas_count_read/,uncore_imc_0/cas_count_write/ -I 1000 ...

Each memory controller has its own PMU.  Measuring the complete system
bandwidth would require specifying all imc PMUs (see perf list output),
and adding the values together.

This example measures the combined core power every second

  perf stat -I 1000 -e power/energy-cores/  -a

ACCESS RESTRICTIONS
-------------------

For non root users generally only context switched PMU events are available.
This is normally only the events in the cpu PMU, the predefined events
like cycles and instructions and some software events.

Other PMUs and global measurements are normally root only.
Some event qualifiers, such as "any", are also root only.

This can be overriden by setting the kernel.perf_event_paranoid
sysctl to -1, which allows non root to use these events.

For accessing trace point events perf needs to have read access to
/sys/kernel/debug/tracing, even when perf_event_paranoid is in a relaxed
setting.

TRACING
-------

Some PMUs control advanced hardware tracing capabilities, such as Intel PT,
that allows low overhead execution tracing.  These are described in a separate
intel-pt.txt document.

PARAMETERIZED EVENTS
--------------------

Some pmu events listed by 'perf-list' will be displayed with '?' in them. For
example:

  hv_gpci/dtbp_ptitc,phys_processor_idx=?/

This means that when provided as an event, a value for '?' must
also be supplied. For example:

  perf stat -C 0 -e 'hv_gpci/dtbp_ptitc,phys_processor_idx=0x2/' ...

EVENT GROUPS
------------

Perf supports time based multiplexing of events, when the number of events
active exceeds the number of hardware performance counters. Multiplexing
can cause measurement errors when the workload changes its execution
profile.

When metrics are computed using formulas from event counts, it is useful to
ensure some events are always measured together as a group to minimize multiplexing
errors. Event groups can be specified using { }.

  perf stat -e '{instructions,cycles}' ...

The number of available performance counters depend on the CPU. A group
cannot contain more events than available counters.
For example Intel Core CPUs typically have four generic performance counters
for the core, plus three fixed counters for instructions, cycles and
ref-cycles. Some special events have restrictions on which counter they
can schedule, and may not support multiple instances in a single group.
When too many events are specified in the group none of them will not
be measured.

Globally pinned events can limit the number of counters available for
other groups. On x86 systems, the NMI watchdog pins a counter by default.
The nmi watchdog can be disabled as root with

	echo 0 > /proc/sys/kernel/nmi_watchdog

Events from multiple different PMUs cannot be mixed in a group, with
some exceptions for software events.

LEADER SAMPLING
---------------

perf also supports group leader sampling using the :S specifier.

  perf record -e '{cycles,instructions}:S' ...
  perf report --group

Normally all events in a event group sample, but with :S only
the first event (the leader) samples, and it only reads the values of the
other events in the group.

OPTIONS
-------

Without options all known events will be listed.

To limit the list use:

. 'hw' or 'hardware' to list hardware events such as cache-misses, etc.

. 'sw' or 'software' to list software events such as context switches, etc.

. 'cache' or 'hwcache' to list hardware cache events such as L1-dcache-loads, etc.

. 'tracepoint' to list all tracepoint events, alternatively use
  'subsys_glob:event_glob' to filter by tracepoint subsystems such as sched,
  block, etc.

. 'pmu' to print the kernel supplied PMU events.

. If none of the above is matched, it will apply the supplied glob to all
  events, printing the ones that match.

. As a last resort, it will do a substring search in all event names.

One or more types can be used at the same time, listing the events for the
types specified.

Support raw format:

. '--raw-dump', shows the raw-dump of all the events.
. '--raw-dump [hw|sw|cache|tracepoint|pmu|event_glob]', shows the raw-dump of
  a certain kind of events.

SEE ALSO
--------
linkperf:perf-stat[1], linkperf:perf-top[1],
linkperf:perf-record[1],
http://www.intel.com/sdm/[Intel® 64 and IA-32 Architectures Software Developer's Manual Volume 3B: System Programming Guide],
http://support.amd.com/us/Processor_TechDocs/24593_APM_v2.pdf[AMD64 Architecture Programmer’s Manual Volume 2: System Programming]