pfm_get_event_info(3) — Linux manual page


LIBPFM(3)               Linux Programmer's Manual              LIBPFM(3)

NAME         top

       pfm_get_event_info - get event information

SYNOPSIS         top

       #include <perfmon/pfmlib.h>

       int pfm_get_event_info(int idx, pfm_os_t os, pfm_event_info_t *info);

DESCRIPTION         top

       This function returns in info information about a specific event
       designated by its opaque unique identifier in idx for the
       operating system specified in os.

       The pfm_event_info_t structure is defined as follows:
       typedef struct {
               const char              *name;
               const char              *desc;
               const char              *equiv;
               size_t              size;
               uint64_t                code;
               pfm_pmu_t               pmu;
               pfm_dtype_t             dtype
               int                     idx;
               int                     nattrs;
               struct {
                 unsigned int is_precise:1;
                 unsigned int reserved_bits:31;
       } pfm_event_info_t;

       The fields of this structure are defined as follows:

       name   This is the name of the event. This is a read-only string.

       desc   This is the description of the event. This is a read-only
              string. It may contain multiple sentences.

       equiv  Certain events may be just variations of actual events.
              They may be provided as handy shortcuts to avoid supplying
              a long list of attributes. For those events, this field is
              not NULL and contains the complete equivalent event

       code   This is the raw event code. It should not be confused with
              the encoding of the event. This field represents only the
              event selection code, it does not include any unit mask or
              attribute settings.

       pmu    This is the identification of the PMU model this event
              belongs to. It is of type pfm_pmu_t. Using this value and
              the pfm_get_pmu_info function, it is possible to get PMU

       dtype  This field returns the representation of the event data.
              By default, it is PFM_DATA_UINT64.

              idx This is the event unique opaque identifier. It is
              identical to the idx passed to the call and is provided
              for completeness.

       nattrs This is the number of attributes supported by this event.
              Attributes may be unit masks or modifiers. If the event
              has not attribute, then the value of this field is simply

       size   This field contains the size of the struct passed. This
              field is used to provide for extensibility of the struct
              without compromising backward compatibility.  The value
              should be set to sizeof(pfm_event_info_t). If instead, a
              value of 0 is specified, the library assumes the struct
              passed is identical to the first ABI version which size is
              PFM_EVENT_INFO_ABI0. Thus, if fields were added after the
              first ABI, they will not be set by the library. The
              library does check that bytes beyond what is implemented
              are zeroes.

              This bitfield indicates whether or not the event support
              precise sampling.  Precise sampling is a hardware
              mechanism that avoids instruction address skid when using
              interrupt-based sampling. When the event has umasks, this
              field means that at least one umask supports precise
              sampling. On Intel X86 processors, this indicates whether
              the event supports Precise Event-Based Sampling (PEBS).

              This bitfield indicates whether or not the event includes
              occurrences happening during speculative execution for
              both wrong and correct path. Given that this kind of event
              information is not always available from vendors, this
              field uses multiple bits. A value of
              PFM_EVENT_INFO_SPEC_NA indicates that speculation
              information is not available. A value of
              PFM_EVENT_INFO_SPEC_TRUE indicates that the event count
              during speculative execution. A value of
              PFM_EVENT_INFO_SPEC_FALS indicates that the event does not
              count during speculative execution.

       The pfm_os_t enumeration provides the following choices:

              The returned information pertains only to what the PMU
              hardware exports.  No operating system attributes is taken
              into account.

              The returned information includes the actual PMU hardware
              and the additional attributes exported by the perf_events
              kernel interface.  The perf_event attributes pertain only
              the PMU hardware.  In case perf_events is not detected, an
              error is returned.

              The returned information includes all of what is already
              provided by PFM_OS_PERF_EVENT plus all the software
              attributes controlled by perf_events, such as sampling
              period, precise sampling.

RETURN         top

       If successful, the function returns PFM_SUCCESS and event
       information in info, otherwise it returns an error code.

ERRORS         top

              Library has not been initialized properly.

              The idx argument is invalid or info is NULL or size is not

              The requested os is not detected or supported.

AUTHOR         top

       Stephane Eranian <>

COLOPHON         top

       This page is part of the perfmon2 (a performance monitoring
       library) project.  Information about the project can be found at
       ⟨⟩.  If you have a bug report for
       this manual page, send it to  This page was obtained
       from the project's upstream Git repository
       ⟨git:// perfmon2-libpfm4⟩ on
       2023-12-22.  (At that time, the date of the most recent commit
       that was found in the repository was 2023-09-28.)  If you
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                             December, 2009                    LIBPFM(3)