Provided by: libpfm4-dev_4.7.0-4_amd64 
NAME
pfm_get_event_attr_info - get event attribute information
SYNOPSIS
#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
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:
PFM_OS_NONE
The returned information pertains only to what the PMU hardware exports. No
operating system attributes is taken into account.
PFM_OS_PERF_EVENT
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.
PFM_OS_PERF_EVENT_EXT
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 reserved:30;
};
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 string.
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:
PFM_ATTR_UMASK
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.
PFM_ATTR_MOD_BOOL
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.
PFM_ATTR_MOD_INTEGER
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 completeness.
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.
is_precise
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).
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:
PFM_ATTR_CTRL_UNKNOWN
The source controlling the attribute is not known.
PFM_ATTR_CTRL_PMU
The attribute is controlled by the PMU hardware.
PFM_ATTR_CTRL_PERF_EVENT
The attribute is controlled by the perf_events kernel interface.
reserved
These fields must be set to zero.
RETURN
If successful, the function returns PFM_SUCCESS and attribute information in info,
otherwise it returns an error code.
ERRORS
PFMLIB_ERR_NOINIT
Library has not been initialized properly.
PFMLIB_ERR_INVAL
The idx or attr arguments are invalid or info is NULL or size is not zero.
PFM_ERR_NOTSUPP
The requested os layer has not been detected on the host system.
AUTHOR
Stephane Eranian <eranian@gmail.com>
December, 2009 LIBPFM(3)