__pmLocalPMDA(3) — Linux manual page


PMLOCALPMDA(3)            Library Functions Manual            PMLOCALPMDA(3)

NAME         top

       __pmLocalPMDA  -  change  the table of DSO PMDAs for PM_CONTEXT_LOCAL

C SYNOPSIS         top

       #include "pmapi.h"
       #include "libpcp.h"

       int __pmLocalPMDA(int op, int domain, const char *name,
               const char *init);

       cc ... -lpcp

CAVEAT         top

       This documentation is intended for internal Performance Co-Pilot
       (PCP) developer use.

       These interfaces are not part of the PCP APIs that are guaranteed to
       remain fixed across releases, and they may not work, or may provide
       different semantics at some point in the future.

DESCRIPTION         top

       PCP contexts of type PM_CONTEXT_LOCAL are used by clients that wish
       to fetch metrics directly from one or more PMDAs on the local host
       without involving pmcd(1).  A PMDA that is to be used in this way
       must have been built as a Dynamic Shared Object (DSO).

       Historically the table of PMDAs available for use with
       PM_CONTEXT_LOCAL was hardcoded to the following:

       * The PMDA (or PMDAs) that export the operating system performance
         data and data about process activity.
       * The mmv PMDA.
       * The sample PMDA provided $PCP_LITE_SAMPLE or $PMDA_LOCAL_SAMPLE is
         set in the environment - used mostly for QA and testing.

       The initial table of PMDAs available for use with PM_CONTEXT_LOCAL is
       now generated dynamically from all those PMDAs that have been
       installed as DSOs on the local host.  The one exception is the
       ``pmcd'' PMDA which only operates correctly in the address space of a
       running pmcd(1) process and so is not available to an application
       using a PM_CONTEXT_LOCAL context.

       __pmLocalPMDA provides a number of services to amend the table of
       PMDAs available for use with PM_CONTEXT_LOCAL.

       The op argument specifies the what should be done and takes one of
       the following values and actions:

       PM_LOCAL_ADD    Append an entry to the table for the PMDA with a
                       Performance Metrics Domain (PMD) of domain, the path
                       to the DSO PMDA is given by path and the PMDA's
                       initialization routine is init.

       PM_LOCAL_DEL    Removes all entries in the table where the domain
                       matches, or the path matches.  Setting the arguments
                       domain to -1 or path to NULL to force matching on the
                       other argument.  The init argument is ignored.

       PM_LOCAL_CLEAR  Remove all entries from the table.  All the other
                       arguments are ignored in this case.

       The domain, name and init arguments have similar syntax and semantics
       to the associated fields in the pmcd(1) configuration file.  The one
       difference is the path argument which is used by __pmLocalPMDA to
       find a likely looking DSO by searching in this order:
       $PCP_PMDAS_DIR/path, path, $PCP_PMDAS_DIR/path.dso-suffix and finally
       path.dso-suffix (dso-suffix is the local platform specific default
       file name suffix for a DSO, e.g.  so for Linux, dylib for Mac OS X,
       dll for Windows, etc.).

RETURN VALUE         top

       In most cases, __pmLocalPMDA returns 0 to indicate success.  If op is
       invalid, then the return value is PM_ERR_CONV else if there is no
       matching table entry found for a PM_LOCAL_DEL operation, PM_ERR_INDOM
       is returned.

SEE ALSO         top

       pmcd(1), PMAPI(3), pmNewContext(3) and __pmSpecLocalPMDA(3).

COLOPHON         top

       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
       2020-08-13.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-08-11.)  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                                          PMLOCALPMDA(3)