.TH LIBPFM 3  "January, 2011" "" "Linux Programmer's Manual"

.SH NAME

pfm_get_os_event_encoding \- get event encoding for a specific operating system

.SH SYNOPSIS

.nf

.B #include <perfmon/pfmlib.h>

.sp

.BI "int pfm_get_os_event_encoding(const char *" str ", int " dfl_plm ", pfm_os_t " os ",  void *" arg ");"

.sp

.SH DESCRIPTION

This is the key function to retrieve the encoding of an event for a specific operating system

interface. The event string passed in \fBstr\fR is parsed and encoded for the operating system

specified by \fBos\fR. Only one event per call can be encoded. As such, \fBstr\fR can contain only

one symbolic event name. The event is encoded to monitor at the privilege levels specified

by the \fBdfl_plm\fR mask, if supported, otherwise this parameter is ignored. The operating

system specific input and output arguments are passed in \fBarg\fR.

The event string, \fBstr\fR, 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 \fBstr\fR but only the first event is encoded.

The following values are supported for \fBos\fR:

.TP

.B PFM_OS_NONE

This value causes the event to be encoded purely as specified by the PMU hardware. The \fBarg\fR

argument must be a pointer to a \fBpfm_raw_pmu_encode_arg_t\fR structure which is defined as follows:

.nf

typedef struct {

    uint64_t    *codes;

    char        **fstr;

    size_t      size;

    int         count;

    int         idx;

} pfm_pmu_encode_arg_t;

.fi

The fields are defined as follows:

.RS

.TP

.B codes

A pointer to an array of 64-bit values. On input, if \fBcodes\fR is NULL, then the library allocates

whatever is necessary to store the encoding of the event. If \fBcodes\fR is not NULL on input, then

\fBcount\fR must reflect its actual number of elements. If \fBcount\fR is big enough, the library

stores the encoding at the address provided.  Otherwise, an error is returned.

.TP

.B count

On input, the field contains the maximum number of elements in the array \fBcodes\fR. Upon return,

it contains the number of actual entries in \fBcodes\fR. If \fBcodes\fR is NULL, then count must

be zero.

.TP

.B 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 \fBfstr\fR was not NULL, then the string pointer passed on entry points to the event string. The string is

dynamically allocated and \fBmust\fR eventually be freed by the caller. If \fBfstr\fR was NULL on entry, then nothing is returned

in this field. The typical calling sequence looks as follows:

.nf

   char *fstr = NULL

   pfm_pmu_encode_arg_t arg;

   arg.fstr = &fst;;

   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);

   }

.fi

.TP

.B 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 \fBsizeof(pfm_pmu_encode_arg_t)\fR. If instead, a value of

\fB0\fR is specified, the library assumes the struct passed is identical to the

first ABI version which size is \fBPFM_RAW_ENCODE_ABI0\fR. 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.

.TP

.B idx

Upon return, this field contains the opaque unique identifier for the event described in \fBstr\fR.

This index can be used to retrieve information about the event using \fBpfm_get_event_info()\fR, for instance.

.RE

.TP

.B 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 \fBarg\fR must be a pointer to a \fBpfm_perf_encode_arg_t\fR 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 \fBPFM_OS_PERF_EVENT_EXT\fR extends

\fBPFM_OS_EVENT\fR to add modifiers controlled only by the perf_event interface, such as sampling period (\fBperiod\fR),

frequency (\fBfreq\fR) and exclusive resource access (\fBexcl\fR).

.nf

typedef struct {

    struct perf_event_attr *attr;

    char **fstr;

    size_t size;

    int idx;

    int cpu;

    int flags;

} pfm_perf_encode_arg_t;

.fi

The fields are defined as follows:

.RS

.TP

.B 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.

.TP

.B fstr

Same behavior as is described for PFM_OS_NONE above.

.TP

.B 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 \fBsizeof(pfm_perf_encode_arg_t)\fR. If instead, a value of

\fB0\fR is specified, the library assumes the struct passed is identical to the

first ABI version which size is \fBPFM_PERF_ENCODE_ABI0\fR. 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.

.TP

.B idx

Upon return, this field contains the opaque unique identifier for the event described in \fBstr\fR.

This index can be used to retrieve information about the event using \fBpfm_get_event_info()\fR, for instance.

.TP

.B cpu

Not used yet.

.TP

.B flags

Not used yet.

.RE

.PP

Here is a example of how this function could be used with PFM_OS_NONE:

.nf

#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;

}

.fi

.SH RETURN

The function returns in \fBarg\fR the encoding of the event for the os passed in \fBos\fR. The content

of \fBarg\fR depends on the \fBos\fR argument. Upon success, \fBPFM_SUCCESS\fR is returned otherwise

a specific error code is returned.

.SH ERRORS

.TP

.B PFM_ERR_TOOSMALL

The \fBcode\fR argument is too small for the encoding.

.TP

.B PFM_ERR_INVAL

The \fBcode\fR or \fBcount\fR argument is \fBNULL\fR or the \fBstr\fR contains more than one symbolic event.

.TP

.B PFM_ERR_NOMEM

Not enough memory.

.TP

.B PFM_ERR_NOTFOUND

Event not found.

.TP

.B PFM_ERR_ATTR

Invalid event attribute (unit mask or modifier)

.TP

.B PFM_ERR_ATTR_VAL

Invalid modifier value.

.TP

.B PFM_ERR_ATTR_SET

attribute already set, cannot be changed.

.TP

.B PFM_ERR_ATTR_UMASK

Missing unit mask.

.TP

.B PFM_ERR_ATTR_FEATCOMB

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

.SH AUTHOR

Stephane Eranian <eranian@gmail.com>

.PP