qmcindom(3) — Linux manual page


QMC_INDOM(3)              Library Functions Manual              QMC_INDOM(3)

NAME         top

       QmcIndom - container for a instance domain description

C++ SYNOPSIS         top

       #include <QmcIndom.h>

       CC ... -lqmc -lpcp

DESCRIPTION         top

       A QmcIndom object represents a PMAPI(3) instance domain.  This
       includes a description of all the instances in the instance domain.

       A QmcInstance is a structure used to describe each instance in the
       instance domain.  This includes:

          - internal identifier. If this is less than zero, the instance is
          treated as a NULL entry in the instance table.

          - external name

          - reference count, ie. the number of QmcMetric objects referring
          to this instance.

          - the likely position of the instance in the pmResult from a
          pmFetch(3).  This is also used to indicate the position of the
          next NULL instance in the instance table, if this entry is also

          - a flag indicating if the instance was in the last pmGetInDom(3).

       The QmcIndom object has a list of QmcInstance structures, and various
       flags and counters to support dynamic instance domains where
       instances may come and go with each fetch and efficient profile

CONSTRUCTORS         top

       QmcIndom::QmcIndom(int type, QmcDesc &desc);
           Calls pmGetInDom(3) and pmGetInDomArchive(3) for host and archive
           contexts to obtain the entire instance list for the instance
           domain of type and identified in desc.

DYNAMIC INDOMS         top

       The support of dynamic instance domains for live contexts is complex
       since many metrics may be referencing any of the instances in the
       domain.  Therefore the instance list may be sparse as the position of
       instances in the list must be maintained.

       When the instance domain is updated, instances may be removed from
       the list if they are not in the new instance list (as returned by
       pmGetInDom(3)) and is not referenced by any metrics. Each instance in
       the new list is then compared with the old list to determine which
       instances are still active, and any new instances need to be added.
       An instance is considered the same if both the internal and external
       identifiers are the same.  New instances are first inserted into
       positions of deleted instances before being appended to the list.

       This algorithm is expensive (potentially O(N^2)).

       bool changed() const;
           Returns true if the instance domain may have changed in the last

       void newFetch();
           Reset the flags that may have indicated that the instance domain
           had changed.  This is called by QmcContext::fetch.

       void hasChanged();
           Set the flags to indicate that the instance domain may have
           changed.  This is called by QmcMetric::extractValues.

       int update();
           Update the instance domain as described above. On subsequent
           calls, before the next fetch, this method will remove any
           instances that are no longer referenced without updating the
           instance list with a pmGetInDom(3) call.

       uint_t numInsts() const;
           Returns the number of instances that are not NULL.

       uint_t numActiveInsts() const;
           Returns the number of instances that are active according to the
           last QmcIndom::update call.

       uint_t listLen() const;
           Returns the length of the instance list, including NULL

PROFILES         top

       The algorithm for determining the most compact profile uses the
       number of instances (_instances.length()), the number of referenced
       instances (_count), the number of active instances (_numActive) and
       the number of referenced active instances (_numActiveRef).

               if (all active instances are referenced
                   or there are no active instances)

                       request all instances implicitly

               else if (the number of referenced instances
                        is less than the number of active
                        instances that are not referenced)

                       delete all instances from profile
                       add all referenced instances


                       add all instances to profile
                       delete all instances that are not referenced

       bool diffProfile() const;
           Returns true if the profile has potentially changed since the
           last call to QmcIndom::genProfile.

       int genProfile();
           Generates a new profile for the instance domain. a PMAPI(3) error
           code is returned if the profile failed.

SEE ALSO         top

       PMAPI(3), QMC(3), QmcContext(3), QmcDesc(3), QmcMetric(3),
       pmFetch(3), pmflush(3), pmGetInDom(3), pmGetInDomArchive(3) and

DIAGNOSTICS         top

       Error messages are generated using pmprintf(3) but are not flushed.
       It is the responsibility of the user to call pmflush(3) to output any

       Additional diagnostics may be activated by adding the options pmc
       and/or indom to the global debugging specification, as described in

BUGS         top

       User's have no control over the algorithm used to generate the
       profile. In the case of proc metrics, an implicit profile could be
       generated if all process instances are required, even though this
       will result in no values being returned in the fetch.

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
       2020-07-14.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-07-14.)  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                 SGI                        QMC_INDOM(3)