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NAME | SYNOPSIS | DESCRIPTION | RETURN | ERRORS | AUTHOR | COLOPHON |
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LIBPFM(3) Linux Programmer's Manual LIBPFM(3)
pfm_get_os_event_encoding - get event encoding for a specific
operating 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. Only one event per call can be encoded. As such, str can
contain only one symbolic event name. 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_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=%s\n", 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_PERF_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_pmu_encode_t arg;
int ret;
ret = pfm_initialize();
if (ret != PFMLIB_SUCCESS)
errx(1, "cannot initialize library %s", pfm_strerror(ret));
memset(&arg, 0, sizeof(arg));
ret = pfm_get_os_event_encoding("RETIRED_INSTRUCTIONS", PFM_PLM3, PFM_OS_NONE, &arg);
if (ret != PFM_SUCCESS)
err(1", cannot get encoding %s", pfm_strerror(ret));
for(i=0; i < arg.count; i++)
printf("count[%d]=0x%"PRIx64"\n", i, arg.codes[i]);
free(arg.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 or the str contains
more than one symbolic event.
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 <[email protected]>
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
[email protected]. This page was obtained
from the project's upstream Git repository
⟨git://git.code.sf.net/p/perfmon2/libpfm4 perfmon2-libpfm4⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-04-24.) If you
discover 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 [email protected]
January, 2011 LIBPFM(3)
Pages that refer to this page: pfm_get_event_encoding(3), pfm_get_perf_event_encoding(3)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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