1PMDACHILDREN(3) Library Functions Manual PMDACHILDREN(3)
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6 pmdaChildren - translate a PMID to a set of dynamic performance metric
7 names
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10 #include <pcp/pmapi.h>
11 #include <pcp/pmda.h>
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13 int pmdaChildren(char *name, int traverse, char ***offspring,
14 int **status, pmdaExt *pmda);
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16 cc ... -lpcp_pmda -lpcp
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19 As part of the Performance Metrics Domain Agent (PMDA) API (see PM‐
20 DA(3)), pmdaChildren is the generic callback for returning dynamic met‐
21 ric names (and their status) that are descendants of name.
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23 Because implementing dynamic performance metrics requires specific PMDA
24 support, and the facility is an optional component of a PMDA (most PM‐
25 DAs do not support dynamic performance metrics), pmdaChildren is a
26 skeleton implementation that returns PM_ERR_NAME.
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28 A PMDA that supports dynamic performance metrics will provide a private
29 callback that replaces pmdaChildren (by assignment to ver‐
30 sion.four.children of the pmdaInterface structure) and takes the ini‐
31 tial metric name and returns names via offspring[] and the leaf or non-
32 leaf status of each via status[].
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34 If traverse is 0, then the behaviour is akin to pmGetChildren(3) and
35 offspring[] contains the relative name component for the immediate de‐
36 scendants of name.
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38 If traverse is 1, then the behaviour is akin to pmTraversePMNS(3) and
39 offspring[] contains the absolute names of all dynamic metrics that are
40 decedents of name.
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42 The resulting list of pointers offspring and the values (the names)
43 that the pointers reference will have been allocated by pmdaChildren
44 with a single call to malloc(3), and the caller of pmdaChildren will
45 call free(offspring) to release the space when it is no longer re‐
46 quired. The same holds true for the status array.
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49 pmdaChildren returns PM_ERR_NAME if the name is not recognized or can‐
50 not be translated, otherwise the number of descendent metric names
51 found.
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54 The PMDA must be using PMDA_PROTOCOL_4 or later, as specified in the
55 call to pmdaDSO(3) or pmdaDaemon(3).
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58 PMAPI(3), PMDA(3), pmdaDaemon(3), pmdaDSO(3), pmdaMain(3), pmGetChil‐
59 dren(3) and pmTraversePMNS(3).
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63Performance Co-Pilot PCP PMDACHILDREN(3)