pmunpackeventrecords(3) — Linux manual page

PMUNPACKEVENTRECORDS(3) Library Functions Manual PMUNPACKEVENTRECORDS(3)

NAME

       pmUnpackEventRecords, pmUnpackHighResEventRecords - unpack event
       records

C SYNOPSIS

       #include <pcp/pmapi.h>

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

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

       cc ... -lpcp

DESCRIPTION

       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
       PM_TYPE_HIGHRES_EVENT.

       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

       The following errors are possible:

       PM_ERR_CONV
              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.

       PM_ERR_INST
              The value associated with vsp is not singular as expected.

       PM_ERR_TYPE
              vsp is not a value of type PM_TYPE_EVENT.

       PM_ERR_TOOSMALL
              The value identified by vsp 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/pmHighResEventArray structure is negative, or
              the number of missed event records in the array is
              negative.

       PM_ERR_TOOBIG
              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.

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

       other values < 0
              refer to pmErrStr(3).

SEE ALSO

       PMAPI(3) and pmFreeEventResult(3).

COLOPHON

       This page is part of the PCP (Performance Co-Pilot) project.
       Information about the project can be found at 
       ⟨http://www.pcp.io/⟩.  If you have a bug report for this manual
       page, send it to pcp@groups.io.  This page was obtained from the
       project's upstream Git repository
       ⟨https://github.com/performancecopilot/pcp.git⟩ on 2024-06-14.
       (At that time, the date of the most recent commit that was found
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       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

Performance Co-Pilot               PCP           PMUNPACKEVENTRECORDS(3)

Pages that refer to this page: pmextractvalue(3), pmfreeeventresult(3)

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