pmdachildren(3) — Linux manual page


PMDACHILDREN(3)         Library Functions Manual         PMDACHILDREN(3)

NAME         top

       pmdaChildren - translate a PMID to a set of dynamic performance
       metric names

C SYNOPSIS         top

       #include <pcp/pmapi.h>
       #include <pcp/pmda.h>

       int pmdaChildren(char *name, int traverse, char ***offspring,
               int **status, pmdaExt *pmda);

       cc ... -lpcp_pmda -lpcp

DESCRIPTION         top

       As part of the Performance Metrics Domain Agent (PMDA) API (see
       PMDA(3)), pmdaChildren is the generic callback for returning
       dynamic metric names (and their status) that are descendants of

       Because implementing dynamic performance metrics requires
       specific PMDA support, and the facility is an optional component
       of a PMDA (most PMDAs do not support dynamic performance
       metrics), pmdaChildren is a skeleton implementation that returns

       A PMDA that supports dynamic performance metrics will provide a
       private callback that replaces pmdaChildren (by assignment to
       version.four.children of the pmdaInterface structure) and takes
       the initial metric name and returns names via offspring[] and the
       leaf or non-leaf status of each via status[].

       If traverse is 0, then the behaviour is akin to pmGetChildren(3)
       and offspring[] contains the relative name component for the
       immediate descendants of name.

       If traverse is 1, then the behaviour is akin to pmTraversePMNS(3)
       and offspring[] contains the absolute names of all dynamic
       metrics that are decedents of name.

       The resulting list of pointers offspring and the string values
       (the names) that the pointers reference will have been allocated
       by pmdaChildren with a single call to malloc(3), and the caller
       of pmdaChildren will call free(offspring) to release the space
       when it is no longer required.  The same holds true for the
       status array, namely the caller of pmdaChildren will call
       free(status) to release the space when it is no longer required.

CAVEAT         top

       The PMDA must be using PMDA_PROTOCOL_4 or later, as specified in
       the call to pmdaDSO(3) or pmdaDaemon(3).

DIAGNOSTICS         top

       pmdaChildren returns PM_ERR_NAME if the name is not recognized or
       cannot be translated, otherwise the number of descendent metric
       names found.

SEE ALSO         top

       PMAPI(3), PMDA(3), pmdaDaemon(3), pmdaDSO(3), pmdaMain(3),
       pmGetChildren(3) and pmTraversePMNS(3).

COLOPHON         top

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

Pages that refer to this page: pmdamain(3)