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NAME | SYNOPSIS | DESCRIPTION | RETURN | ERRORS | AUTHOR | COLOPHON |
LIBPFM(3) Linux Programmer's Manual LIBPFM(3)
pfm_get_os_event_encoding - get event encoding for a specific operat‐
ing system
#include <perfmon/pfmlib.h>
int pfm_get_os_event_encoding(const char *str, int dfl_plm, pfm_os_t os, void *arg);
This is the key function to retrieve the encoding of an event for a
specific operating system interface. The event string passed in str
is parsed and encoded for the operating system specified by os. The
event is encoded to monitor at the privilege levels specified by the
dfl_plm mask, if supported, otherwise this parameter is ignored. The
operating system specific input and output arguments are passed in
arg.
The event string, str, may contains sub-event masks (umask) and any
other supported modifiers. Only one event is parsed from the string.
For convenience, it is possible to pass a comma-separated list of
events in str but only the first event is encoded.
The following values are supported for os:
PFM_OS_NONE
This value causes the event to be encoded purely as specified
by the PMU hardware. The arg argument must be a pointer to a
pfm_raw_pmu_encode_arg_t structure which is defined as
follows:
typedef struct {
uint64_t *codes;
char **fstr;
size_t size;
int count;
int idx;
} pfm_pmu_encode_arg_t;
The fields are defined as follows:
codes A pointer to an array of 64-bit values. On input, if
codes is NULL, then the library allocates whatever is
necessary to store the encoding of the event. If codes
is not NULL on input, then count must reflect its
actual number of elements. If count is big enough, the
library stores the encoding at the address provided.
Otherwise, an error is returned.
count On input, the field contains the maximum number of
elements in the array codes. Upon return, it contains
the number of actual entries in codes. If codes is
NULL, then count must be zero.
fstr If the caller is interested in retrieving the fully
qualified event string where all used unit masks and
all modifiers are spelled out, this field must be set
to a non-null address of a pointer to a string (char
**). Upon return, if fstr was not NULL, then the
string pointer passed on entry points to the event
string. The string is dynamically allocated and must
eventually be freed by the caller. If fstr was NULL on
entry, then nothing is returned in this field. The
typical calling sequence looks as follows:
char *fstr = NULL
pfm_pmu_encode_arg_t arg;
arg.fstr = &fstr;
ret = pfm_get_os_event_encoding("event",
PFM_PLM0|PFM_PLM3,
PFM_OS_NONE,
&e);
if (ret == PFM_SUCCESS) {
printf("fstr=%s0, fstr);
free(fstr);
}
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_pmu_encode_arg_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_RAW_ENCODE_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.
idx Upon return, this field contains the opaque unique
identifier for the event described in str. This index
can be used to retrieve information about the event
using pfm_get_event_info(), for instance.
PFM_OS_PERF_EVENT, PFM_OS_PERF_EVENT_EXT
This value causes the event to be encoded for the perf_event
Linux kernel interface (available since 2.6.31). The arg must
be a pointer to a pfm_perf_encode_arg_t structure. The
PFM_OS_PERF_EVENT layer provides the modifiers exported by the
underlying PMU hardware, some of which may actually be
overridden by the perf_event interface, such as the monitoring
privilege levels. The PFM_OS_PERF_EVENT_EXT extends
PFM_OS_EVENT to add modifiers controlled only by the
perf_event interface, such as sampling period (period),
frequency (freq) and exclusive resource access (excl).
typedef struct {
struct perf_event_attr *attr;
char **fstr;
size_t size;
int idx;
int cpu;
int flags;
} pfm_perf_encode_arg_t;
The fields are defined as follows:
attr A pointer to a struct perf_event_attr as defined in
perf_event.h. This field cannot be NULL on entry. The
struct is not completely overwritten by the call. The
library only modifies the fields it knows about,
thereby allowing perf_event ABI mismatch between caller
and library.
fstr Same behavior as is described for PFM_OS_NONE above.
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_perf_encode_arg_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_PERF_ENCODE_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.
idx Upon return, this field contains the opaque unique
identifier for the event described in str. This index
can be used to retrieve information about the event
using pfm_get_event_info(), for instance.
cpu Not used yet.
flags Not used yet.
Here is a example of how this function could be used with
PFM_OS_NONE:
#include <inttypes.h>
#include <err.h>
#include <perfmon/pfmlib.h>
int main(int argc, char **argv)
{
pfm_raw_pmu_encode_t raw;
int ret;
ret = pfm_initialize();
if (ret != PFMLIB_SUCCESS)
errx(1, "cannot initialize library %s", pfm_strerror(ret));
memset(&raw, 0, sizeof(raw));
ret = pfm_get_os_event_encoding("RETIRED_INSTRUCTIONS", PFM_PLM3, PFM_OS_NONE, &raw);
if (ret != PFM_SUCCESS)
err(1", cannot get encoding %s", pfm_strerror(ret));
for(i=0; i < raw.count; i++)
printf("count[%d]=0x%"PRIx64"\n", i, raw.codes[i]);
free(raw.codes);
return 0;
}
The function returns in arg the encoding of the event for the os
passed in os. The content of arg depends on the os argument. Upon
success, PFM_SUCCESS is returned otherwise a specific error code is
returned.
PFM_ERR_TOOSMALL
The code argument is too small for the encoding.
PFM_ERR_INVAL
The code or count 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.
Stephane Eranian <eranian@gmail.com>
This page is part of the perfmon2 (a performance monitoring library)
project. Information about the project can be found at
⟨http://perfmon2.sourceforge.net/⟩. If you have a bug report for this
manual page, send it to perfmon2-devel@lists.sourceforge.net. This
page was obtained from the project's upstream Git repository
⟨git://git.code.sf.net/p/perfmon2/libpfm4⟩ on 2017-07-05. If you dis‐
cover any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
January, 2011 LIBPFM(3)