NAME | SYNOPSIS | DESCRIPTION | RETURN | ERRORS | AUTHOR | COLOPHON

LIBPFM(3)                 Linux Programmer's Manual                LIBPFM(3)

NAME         top

       pfm_get_os_event_encoding - get event encoding for a specific operat‐
       ing system

SYNOPSIS         top

       #include <perfmon/pfmlib.h>

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

DESCRIPTION         top

       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;
       }

RETURN         top

       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.

ERRORS         top

       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.

AUTHOR         top

       Stephane Eranian <eranian@gmail.com>

COLOPHON         top

       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 2017-03-13.  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)