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LIBPFM

NAME

pfm_get_perf_event_encoding − encode event for perf_event API

SYNOPSIS

#include <perfmon/pfmlib_perf_event.h>

int pfm_get_perf_event_encoding(const char *str, int dfl_plm, struct perf_event_attr *attr, char **fstr, int *idx);

DESCRIPTION

This function can be used in conjunction with the perf_events Linux kernel API which provides access to hardware performance counters, kernel software counters and tracepoints. The function takes an event string in str and a default privilege level mask in dfl_plm and fills out the relevant parts of the perf_events specific data structure in attr.

This function is deprecated. It is superseded by pfm_get_os_event_encoding() with the OS argument set to either PFM_OS_PERF_EVENT or PFM_OS_PERF_EVENT_EXT. Using this function provides extended support for perf_events. Certain perf_event configuration option are only available through this new interface.

The following examples illustrates the transition:

struct perf_event_attr attr;
int i, count = 0;
uint64_t *codes;

memset(&attr, 0, sizeof(attr));

ret = pfm_get_perf_event_encoding("RETIRED_INSTRUCTIONS", PFM_PLM3, &attrs, NULL, NULL);
if (ret != PFM_SUCCESS)
err(1", cannot get encoding %s", pfm_strerror(ret));

is equivalent to:

#include <perfmon/pfmlib_perf_event.h>
struct perf_event_attr attr;
pfm_perf_encode_arg_t arg;

memset(&arg, 0, sizeof(arg));
arg.size = sizeof(arg);
arg.attr = &attr;

ret = pfm_get_os_event_encoding("RETIRED_INSTRUCTIONS", PFM_PLM3, PFM_OS_PERF, &arg);
if (ret != PFM_SUCCESS)
err(1", cannot get encoding %s", pfm_strerror(ret));

The dfl_plm cannot be zero, though it may not necessarily be used by the event.
Depending on the event, combination of the following privilege levels may be used:
PFM_PLM3

Measure at privilege level 3. This usually corresponds to user level. On X86, it corresponds
to privilege levels 3, 2, 1. Check the PMU specific man page to verify if this level
is supported by your PMU model.

PFM_PLM2

Measure at privilege level 2. Check the PMU specific man page to verify if this level
is supported by your PMU model.

PFM_PLM1

Measure at privilege level 1. Check the PMU specific man page to verify if this level
is supported by your PMU model.

PFM_PLM0

Measure at privilege level 0. This usually corresponds to kernel level. Check the PMU
specific man page to verify if this level is supported by your PMU model.

PFM_PLMH

Measure at hypervisor privilege level. This is used in conjunction with hardware virtualization.
Check the PMU specific man page to verify if this level is supported by your PMU model.

If fstr is not NULL, the function will make it point to the fully qualified event string,
i.e., a string with the event name, all unit masks set, and the value of all modifiers.
The library will allocate memory to store the event string but it is the responsibility of the
caller to eventually free that string using free().

If idx is not NULL, it returns the corresponding unique event identifier.

Only select fields are modified by the function, the others are untouched.
The following fields in attr are modified:

type

The type of the event

config

The encoding of the event

exclude_user

Whether or not user level execution should be excluded from monitoring. The definition
of user is PMU model specific.

exclude_kernel

Whether or not kernel level execution should be excluded from monitoring. The definition
of kernel is PMU model specific.

exclude_hv

Whether or not hypervisor level execution should be excluded from monitoring. The definition
of hypervisor is PMU model specific.

By default, if no privilege level modifier is specified in the event string, the library clears
exclude_user
, exclude_kernel and exclude_hv, resulting in the event being
measured at all levels subject to hardware support.

The function is able to work on only one event at a time. For convenience, it accepts
event strings with commas. In that case, it will translate the first event up to the
first comma. This is handy in case tools gets passed events as a comma-separated list.

RETURN

The function returns in attr the perf_event encoding which corresponds to the event string. If idx is not NULL, then it will contain the unique event identifier upon successful return. The value PFM_SUCCESS is returned if successful, otherwise a negative error code is returned.

ERRORS

PFM_ERR_TOOSMALL

The code argument is too small for the encoding.

PFM_ERR_INVAL

The attr argument is NULL.

PFM_ERR_NOMEM

Not enough memory.

PFM_ERR_NOTFOUND

Event not found.

PFM_ERR_ATTR

Invalid event attribute (unit mask or modifier)

PFM_ERR_ATTR_VAL

Invalid modifier value.

PFM_ERR_ATTR_SET

attribute already set, cannot be changed.

PFM_ERR_ATTR_UMASK

Missing unit mask.

PFM_ERR_ATTR_FEATCOMB

Unit masks or features cannot be combined into a single event.

AUTHOR

Stephane Eranian <eranian AT gmail DOT com>

SEE ALSO

pfm_get_os_event_encoding(3)

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