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NAME | C++ SYNOPSIS | DESCRIPTION | CONSTRUCTORS | DYNAMIC INDOMS | PROFILES | DIAGNOSTICS | BUGS | SEE ALSO | COLOPHON |
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QMCINDOM(3) Library Functions Manual QMCINDOM(3)
QmcIndom - container for a instance domain description
#include <QmcIndom.h>
c++ ... -lpcp_qmc -lpcp
A QmcIndom object represents a PMAPI(3) instance domain. This in‐
cludes 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, i.e. the number of QmcMetric objects refer‐
ring 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
NULL.
- a flag indicating if the instance was in the last
pmGetInDom(3).
The QmcIndom object has a list of QmcInstance structures, and var‐
ious flags and counters to support dynamic instance domains where
instances may come and go with each fetch and efficient profile
generation.
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.
The support of dynamic instance domains for live contexts is com‐
plex since many metrics may be referencing any of the instances in
the domain. Therefore the instance list may be sparse as the po‐
sition 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 fetch.
void newFetch();
Reset the flags that may have indicated that the instance do‐
main 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 in‐
stances that are no longer referenced without updating the in‐
stance 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 in‐
stances.
The algorithm for determining the most compact profile uses the
number of instances (_instances.length()), the number of refer‐
enced instances (_count), the number of active instances (_numAc‐
tive) and the number of referenced active instances (_numAc‐
tiveRef).
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
else
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.
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 messages.
Additional diagnostics may be activated by adding the options pmc
and/or indom to the global debugging specification, as described
in pmSetDebug(3).
Users have no control over the algorithm used to generate the pro‐
file. 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.
PMAPI(3), QMC(3), QmcContext(3), QmcDesc(3), QmcMetric(3),
pmFetch(3), pmflush(3), pmGetInDom(3), pmGetInDomArchive(3) and
pmprintf(3).
This page is part of the PCP (Performance Co-Pilot) project. In‐
formation 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
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-08-11.) 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 man-pages@man7.org
Performance Co-Pilot SGI QMCINDOM(3)
Pages that refer to this page: QMC(3), QmcContext(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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