pfm_get_event_attr_info(3) — Linux manual page


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

NAME         top

       pfm_get_event_attr_info - get event attribute information

SYNOPSIS         top

       #include <perfmon/pfmlib.h>

       int pfm_get_event_attr_info(int idx, int attr, pfm_os_t os, pfm_event_attr_info_t *info);

DESCRIPTION         top

       This function returns in info information about the attribute
       designated by attr for the event specified in idx and the os
       layer in os.

       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.

       The pfm_event_attr_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_attr_t              type;
               int                     idx;
               pfm_attr_ctrl_t         ctrl;
               int                     reserved1;
               struct {
                       int             is_dfl:1;
                       int             is_precise:1;
                       int             is_speculative:2;
                       int             reserved:28;
               union {
                       uint64_t        dfl_val64;
                       const char      *dfl_str;
                       int             dfl_bool;
                       int             dfl_int;
       } pfm_event_attr_info_t;

       The fields of this structure are defined as follows:

       name   This is the name of the attribute. This is a read-only

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

       equiv  Certain attributes may be just variations of other
              attributes for the same event.  They may be provided as
              handy shortcuts to avoid supplying a long list of
              attributes.  For those attributes, this field is not NULL
              and contains the complete equivalent attribute string.
              This string, once appended to the event name, may be used
              library calls requiring an event string.

       code   This is the raw attribute code. For PFM_ATTR_UMASK, this
              is the unit mask code. For all other attributes, this is
              an opaque index.

       type   This is the type of the attribute. Attributes represent
              either sub-events or extra filters that can be applied to
              the event. Filters (also called modifiers)  may be tied to
              the event or the PMU register the event is programmed
              into. The type of an attribute determines how it must be
              specified. The following types are defined:

                     This is a unit mask, i.e., a sub-event. It is
                     specified using its name.  Depending on the event,
                     it may be possible to specify multiple unit masks.

                     This is a boolean attribute. It has a value of 0,
                     1, y or n. The value is specified after the equal
                     sign, e.g., foo=1. As a convenience, the equal sign
                     and value may be omitted, in which case this is
                     equivalent to =1.

                     This is an integer attribute. It has a value which
                     must be passed after the equal sign. The range of
                     valid values depends on the attribute and is
                     usually specified in its description.

       idx    This is the attribute index. It is identical to the value
              of attr passed to the call and is provided for

       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_attr_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_ATTR_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.

       is_dfl This field indicates whether or not this attribute is set
              by default. This applies mostly for PFM_ATTR_UMASK. If a
              unit mask is marked as default, and no unit mask is
              specified in the event string, then the library uses it by
              default. Note that there may be multiple defaults per
              event depending on how unit masks are grouped.

              This field indicates whether or not this umask supports
              precise sampling.  Precise sampling is a hardware
              mechanism that avoids instruction address skid when using
              interrupt-based sampling. On Intel X86 processors, this
              field indicates that the umask supports Precise Event-
              Based Sampling (PEBS).

              This bitfield indicates whether or not the attribute
              includes occurrences happening during speculative
              execution for both wrong and correct paths. 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 attribute
              counts during speculative execution. A value of
              PFM_EVENT_INFO_SPEC_FALSE indicates that the attribute
              does not count during speculative execution.

       dfl_val64, dfl_str, dfl_bool, dfl_int
              This union contains the value of an attribute. For
              PFM_ATTR_UMASK, the is the unit mask code, for all other
              types this is the actual value of the attribute.

       ctrl   This field indicates which layer or source controls the
              attribute.  The following sources are defined:

                     The source controlling the attribute is not known.

                     The attribute is controlled by the PMU hardware.

                     The attribute is controlled by the perf_events
                     kernel interface.

              These fields must be set to zero.

RETURN         top

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

ERRORS         top

              Library has not been initialized properly.

              The idx or attr arguments are invalid or info is NULL or
              size is not zero.

              The requested os layer has not been detected on the host

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
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                             December, 2009                    LIBPFM(3)