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linuxdebug/tools/perf/Documentation/perf-list.txt

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null pointer error
2024-07-16 15:50:57 +02:00
perf-list(1)
============
NAME
----
perf-list - List all symbolic event types
SYNOPSIS
--------
[verse]
'perf list' [--no-desc] [--long-desc]
[hw|sw|cache|tracepoint|pmu|sdt|metric|metricgroup|event_glob]
DESCRIPTION
-----------
This command displays the symbolic event types which can be selected in the
various perf commands with the -e option.
OPTIONS
-------
-d::
--desc::
Print extra event descriptions. (default)
--no-desc::
Don't print descriptions.
-v::
--long-desc::
Print longer event descriptions.
--debug::
Enable debugging output.
--details::
Print how named events are resolved internally into perf events, and also
any extra expressions computed by perf stat.
--deprecated::
Print deprecated events. By default the deprecated events are hidden.
--cputype::
Print events applying cpu with this type for hybrid platform
(e.g. --cputype core or --cputype atom)
[[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
W - group is weak and will fallback to non-group if not schedulable,
e - group or event are exclusive and do not share 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 the
Core Complex (CCX) -> Processor x86 Core -> Instruction Based Sampling (IBS)
section of the [AMD Processor Programming Reference (PPR)] relevant to the
family, model and stepping of the processor being used).
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 on x86 CPUs, N is a hexadecimal value that 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 PERF_CTL MSRs (see the
Core Complex (CCX) -> Processor x86 Core -> MSR Registers section of the
[AMD Processor Programming Reference (PPR)] relevant to the family, model
and stepping of the processor being used).
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 ...
It's also possible to use pmu syntax:
perf record -e r1a8 -a sleep 1
perf record -e cpu/r1a8/ ...
perf record -e cpu/r0x1a8/ ...
Some processors, like those from AMD, support event codes and unit masks
larger than a byte. In such cases, the bits corresponding to the event
configuration parameters can be seen with:
cat /sys/bus/event_source/devices/<pmu>/format/<config>
Example:
If the AMD docs for an EPYC 7713 processor describe an event as:
Event Umask Event Mask
Num. Value Mnemonic Description
28FH 03H op_cache_hit_miss.op_cache_hit Counts Op Cache micro-tag
hit events.
raw encoding of 0x0328F cannot be used since the upper nibble of the
EventSelect bits have to be specified via bits 32-35 as can be seen with:
cat /sys/bus/event_source/devices/cpu/format/event
raw encoding of 0x20000038F should be used instead:
perf stat -e r20000038f -a sleep 1
perf record -e r20000038f ...
It's also possible to use pmu syntax:
perf record -e r20000038f -a sleep 1
perf record -e cpu/r20000038f/ ...
perf record -e cpu/r0x20000038f/ ...
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=0x1/ ...
or using extended name syntax
perf stat -e cpu/event=0xa8,umask=0x1,cmask=0x1,name=\'LSD.UOPS_CYCLES:cmask=0x1\'/ ...
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. To simplify creation of multiple events,
prefix and glob matching is supported in the PMU name, and the prefix
'uncore_' is also ignored when performing the match. So the command above
can be expanded to all memory controllers by using the syntaxes:
perf stat -C 0 -a imc/cas_count_read/,imc/cas_count_write/ -I 1000 ...
perf stat -C 0 -a *imc*/cas_count_read/,*imc*/cas_count_write/ -I 1000 ...
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 overridden 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 QUALIFIERS:
It is also possible to add extra qualifiers to an event:
percore:
Sums up the event counts for all hardware threads in a core, e.g.:
perf stat -e cpu/event=0,umask=0x3,percore=1/
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 some 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 an 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.
However, in the case AUX area events (e.g. Intel PT or CoreSight), the AUX
area event must be the leader, so then the second event samples, not the first.
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.
. 'sdt' to list all Statically Defined Tracepoint events.
. 'metric' to list metrics
. 'metricgroup' to list metricgroups with metrics.
. 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],
https://bugzilla.kernel.org/show_bug.cgi?id=206537[AMD Processor Programming Reference (PPR)]