NAME pfm_find_event - search for an event masks¶

SYNOPSIS¶

#include <perfmon/pfmlib.h>

int pfm_find_event(const char *str);

DESCRIPTION¶

This function is used to convert an event string passed in str into an opaque event identifier, i.e., the return value.

Events are first manipulated a strings which contain the event name, sub-event names and optional filters and modifiers. This function analyzes the string and try to find the matching event.

The event string is a structured string and it is composed as follows:

[pmu_name::]event_name[:unit_mask][:modifier|:modifier=val]

The various components are separated by : or ::, they are defined as follows:

pmu_name

This is an optional prefix to designate a specific PMU model. With the prefix the event which matches the event_name is used. In case multiple PMU models are activated, there may be conflict with identical event names to mean the same or different things. In that case, it is necessary to fully specify the event with a pmu_name. That string corresponds to what is returned by pfm_get_pmu_name().

event_name

This is the event name and is required. The library is not case sensitive on event string. The event name must match completely the actual event name; it cannot be a substring.

unit_mask

The optional unit mask which can be considered like a sub-event of the major event. If a event has unit masks, and there is no default, then at least one unit mask must be passed in the string. Multiple unit masks may be specified for a single event.

modifier

A modifier is an optional filter which is provided by the hardware register hosting the event or by the underlying kernel infrastructure. Typical modifiers include privilege level filters. Some modifiers are simple boolean, in which case just passing their names is equivalent to setting their value to true. Other modifiers need a specific value, in which case it is provided after the equal sign. No space is tolerate around the equal sign. The list of modifiers depends on the host PMU and underlying kernel API. They are documented in PMU-specific documentation. Multiple modifiers may be passed. There is not order between unit masks and modifiers.

The library uses the generic term attribute to designate both unit masks and modifiers.

Here are a few examples of event strings:

amd64::RETIRED_INSTRUCTIONS:u

Event RETIRED_INSTRUCTION on AMD64 processor, measure at user privilege level only

RS_UOPS_DISPATCHED:c=1:i:u

Event RS_UOPS_DISPATCHED measured at user privilege level only, and with counter-mask set to 1

For the purpose of this function, only the pmu_name and event_name are considered, everything else is parsed, thus must be valid, but is ignored.

The function searches only for one event per call. As a convenience, the function will identify the event up to the first comma. In other words, if str is equal to "EVENTA,EVENTB", then the function will only look at EVENTA and will not return an error because of invalid event string. This is handy when parsing constant event strings containing multiple, comma-separated, events.

RETURN¶

The function returns the opaque event identifier that corresponds that the event string. In case of error, a negative error code is returned instead.

ERRORS¶

PFMLIB_ERR_NOINIT

The library has not been initialized properly.

PFMLIB_ERR_INVAL

The event string is NULL.

PFMLIB_ERR_NOMEM

The library ran out of memory.

PFMLIB_ERR_NOTFOUND

The event was not found

PFMLIB_ERR_ATTR

Invalid event attribute

PFMLIB_ERR_ATTR_VAL

Invalid event attribute value

PFMLIB_ERR_TOOMANY

Too many event attributes passed

AUTHOR¶

Stephane Eranian <eranian@gmail.com>