pmdaChildren(3) — Linux manual page


PMDACHILDREN(3)           Library Functions Manual           PMDACHILDREN(3)

NAME         top

       pmdaChildren  - translate a PMID to a set of dynamic performance met‐
       ric 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 name.

       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 PM_ERR_NAME.

       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 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.

DIAGNOSTICS         top

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

CAVEAT         top

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

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.
       Information about the project can be found at ⟨⟩.
       If you have a bug report for this manual page, send it to  This page was obtained from the project's upstream
       Git repository ⟨⟩ on
       2020-11-01.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-10-30.)  If you discover 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

Performance Co-Pilot                 PCP                     PMDACHILDREN(3)

Pages that refer to this page: pmdaGetContext(3)pmdamain(3)pmdaMain(3)pmdaSetCheckCallBack(3)pmdaSetDoneCallBack(3)pmdaSetEndContextCallBack(3)pmdaSetResultCallBack(3)