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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
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, i.e. 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 NULL.
- 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 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
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 fetch.
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
instances.
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
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
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.
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.
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 2024-06-14.
(At that time, the date of the most recent commit that was found
in the repository was 2024-06-14.) 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
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 2024-06-26 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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