In some (rare) cases it is helpful to prune the Performance Metrics
Name Space (PMNS) to match the available metrics.
The default PMNS that is accessible to a Performance Metrics
Application Programming Interface (PMAPI) client is provided by the
current PMAPI context:
· for a PMAPI context of type PM_CONTEXT_HOST the PMNS is provided
by pmcd(1) on the associated host and no pruning is required
· for a PMAPI context of type PM_CONTEXT_ARCHIVE the PMNS is stored
within the associated Performance Co-Pilot (PCP) archive log and
no pruning is required
· for a PMAPI context of type PM_CONTEXT_LOCAL at the first PMAPI
call requiring access to the PMNS it is loaded from the default
local location $PCP_VAR_DIR/pmns/root (or $PMNS_DEFAULT) and no
pruning is required.
If the default PMNS is in effect then calling pmTrimNameSpace is a
no-op and returns zero with no change to the PMNS.
PMAPI clients also have the option of over-riding the default PMNS by
loading a local PMNS from a file (see PMNS(5) for the format) by
calling pmLoadASCIINameSpace(3) or pmLoadNameSpace(3) and this is
when some PMNS pruning may be useful.
If a local PMNS is in effect when pmTrimNameSpace is called then the
first action is to restore the PMNS to the state as of the completion
of the last pmLoadASCIINameSpace(3) or pmLoadNameSpace(3), so that
the effects of consecutive calls to pmTrimNameSpace are not additive.
The subsequent actions of pmTrimNameSpace depend on the type of the
current PMAPI context.
· For a context of type PM_CONTEXT_ARCHIVE the local PMNS is trimmed
to exclude metrics for which no description can be found in the
PCP archive log. The PMNS is further trimmed to remove empty
subtrees that do not contain any performance metric. Since PCP
archives usually contain some subset of all metrics named in a
PMNS, pmTrimNameSpace effectively prunes the application's PMNS to
contain only the names of the metrics in the archive.
· For a context of type PM_CONTEXT_HOST or PM_CONTEXT_LOCAL no
further action is required.
On success, pmTrimNameSpace returns zero.
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
email@example.com. This page was obtained from the project's upstream
Git repository ⟨https://github.com/performancecopilot/pcp.git⟩ on
2020-08-13. (At that time, the date of the most recent commit that
was found in the repository was 2020-08-11.) 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
Performance Co-Pilot PCP PMTRIMNAMESPACE(3)