QMC_CONTEXT(3)

NAME
QmcContext - container for a PMAPI context and its metrics

C++ SYNOPSIS
#include <QmcContext.h>

CC ... -lqmc -lpcp

DESCRIPTION
A QmcContext object is a container for a single PMAPI(3) context. The object maintains a list of all the metric descriptors (QmcDesc), instance domains (QmcIndom) and metrics (QmcMetric) using the context to minimize the duplication of these objects.

CONSTRUCTORS
A QmcContext object should be constructed through the QmcGroup::use interface.

DESCRIPTOR LOOKUP
The metric and instance domain descriptors are cached by the QmcContext object to reduce duplicate QmcDesc(3) and QmcIndom(3) objects and PMAPI(3) calls required to create them. Also the mapping from metrics names to pmIDs is also maintained to avoid pmLookupName(3) calls.

int lookupDesc(const char *name, pmID& id);
    Search for the metric name in the name list and set id to the known pmID. If not found, use pmLookupName(3) to get the mapping. If this call fails, the PMAPI(3) error code will be returned.

int lookupDesc(const char *name, uint_t& desc, uint_t& indom);
    Find the index desc and indom to the QmcDesc object and the QmcIndom object for the metric name. The indexes can then be used with QmcContext::desc and QmcContext::indom to obtain references to the real objects. The methods will return a PMAPI(3) error code if the metric descriptor or instance domain could not be obtained.

int lookupDesc(pmID pmid, uint_t& desc, uint_t& indom);
    Find the index desc and indom to the QmcDesc object and the QmcIndom object for the metric pmid. The indexes can then be used with QmcContext::desc and QmcContext::indom to obtain references to the real objects. The methods will return a PMAPI(3) error code if the metric descriptor or instance domain could not be obtained.

SEE ALSO
PMAPI(3), QMC(3), QmcDesc(3), QmcGroup(3), QmcIndom(3), QmcMetric(3), pmflush(3), pmLookupName(3) and pmprintf(3).

DIAGNOSTICS
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 DBG_TRACE_PMC and DBG_TRACE_OPTFETCH to the global pmDebug.