pmunpackeventrecords(3) — Linux manual page



NAME         top

       pmUnpackEventRecords,   pmUnpackHighResEventRecords  -  unpack  event

C SYNOPSIS         top

       #include <pcp/pmapi.h>

       int pmUnpackEventRecords(pmValueSet *vsp, int idx, pmResult ***rap);

       int pmUnpackHighResEventRecords(pmValueSet *vsp, int idx,
       pmHighResResult ***hrap);

       cc ... -lpcp

DESCRIPTION         top

       Event records are encoded as a packed array of records within a
       pmResult using a container metric with a value of type PM_TYPE_EVENT
       , and a pmHighResResult when using a metric of type

       pmUnpackEventRecords and pmUnpackHighResEventRecords may be used to
       unpack event records from a metric value identified by vsp and idx.
       If the metric has a singular value, idx should be 0, else the ordinal
       instance value identified by idx will be unpacked, i.e.
       vsp->vlist[idx].  The unpacked records are turned into either
       pmResult or pmHighResResult structures, one per event record and one
       metric per event parameter, and rap is returned as a pointer to an
       array (NULL pointer terminated) of pointers to the result structures.

       The only difference between the two result types is the timestamp
       scale; the pmHighResResult allows for nanosecond precision, whereas
       pmResult allows for microsecond resolution.

       Some control information from the packed event records is unpacked
       into additional ``anonymous'' metrics as follows:

       1.  If the event record has a non-zero flags value, then the
           corresponding pmResult/pmHighResResult will have the flags value
           encoded with the additional metric event.flags that is inserted
           ahead of all other event parameters.

       2.  If the event record flag is set to PM_EVENT_FLAG_MISSED, then the
           corresponding pmResult/pmHighResResult will have one metric
           event.missed with a value that equals the number of event records
           ``missed'' because either the PMDA could not keep up, or the
           PMAPI client did not collect the event records fast enough.

       pmUnpackEventRecords returns the number of pmResult structures as the
       return value, which is >= 0 for success.  Similarly,
       pmUnpackHighResEventRecords returns the number of pmHighResResult
       structures as the return value, which is >= 0 for success.

       rap and the associated pmResult structures may be freed using the
       convenience function pmFreeEventResult(3).

       Similarly, the hrap and the associated pmHighResResult structures may
       be freed using the convenience function pmFreeHighResEventResult.

RETURN VALUE         top

       The following errors are possible:

                 The values associated with vsp are not encoded using the
                 format PM_VAL_DPTR or PM_VAL_SPTR, or the flags at the head
                 of the event record has an unexpected value.

                 The value associated with vsp is not singular as expected.

                 vsp is not a value of type PM_TYPE_EVENT.

                 The value identified by vbp is not legal because the value
                 length is less than the minimum size, or the number of
                 event records encoded in the (value header)
                 pmEventArray/pmEventHighResArray structure is negative, or
                 the number of missed event records in the array is

                 Either vsp indicates more than one value is present (all
                 the event records are expected to be packed in a single
                 metric value), or when unpacking the event records, the
                 processing continues past the end of the enclosing value.
                 Indicates corruption of the packed event record.

                 Event parameters must have one of the arithmetic types,
                 else PM_TYPE_AGGREGATE, PM_TYPE_STRING or

       other values < 0
                 refer to pmErrStr(3).

SEE ALSO         top

       PMAPI(3) and pmFreeEventResult(3).

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
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Performance Co-Pilot                 PCP             PMUNPACKEVENTRECORDS(3)