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
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
Reset the flags that may have indicated that the instance domain
had changed. This is called by QmcContext::fetch.
Set the flags to indicate that the instance domain may have
changed. This is called by QmcMetric::extractValues.
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
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.
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
Additional diagnostics may be activated by adding DBG_TRACE_PMC and
DBG_TRACE_INDOM to the global pmDebug.
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.
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
firstname.lastname@example.org. This page was obtained from the project's upstream
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Performance Co-Pilot SGI QMC_INDOM(3)