mmv (5) - Linux Manuals
mmv: Memory Mapped Values for Performance Co-Pilot
NAMEmmv - Memory Mapped Values for Performance Co-Pilot
DESCRIPTIONThe files in $PCP_TMP_DIR/mmv are generated by mmv_stats_init() function from libpcp_mmv library. There could be multiple files in this directory, each file representing a single source of the performance metrics. The metrics are harvested by the mmv PMDA which exports them to the rest of the Performance Co-Pilot infrastructure.
FILE FORMATEach file starts with the following header:
The generation numbers are timestamps at the time of file creation, and must match for the file to be considered by the MMV PMDA.
The flags can specify ways in which the client would like the MMV PMDA to behave - e.g. the MMV_FLAG_PROCESS flag specifies that only if the process identified by PID is currently running should those values be exported.
Finally, if set, the cluster identifier is a hint to the MMV PMDA as to what cluster should be used with this application when forming the individual metric identifiers. A performance metric identifier (see PMDA(3)) consists of the PMDA domain number, the cluster number, and the individual item numbers described in the Metrics section.
The header is followed by at least 2 TOC sections: one section for metrics and another for values. The TOC section has the following format:
The section types are:
- 1: Indoms (instance domain definitions)
- 2: Instances
- 3: Metrics (metric definitions)
- 4: Values
- 5: String
The only mandatory sections are Metrics and Values. Indoms and Instances sections only appear if there are metrics with multiple instances. String sections only appear if there are metrics with string values, or when Metrics or Indoms are defined with help text.
The entries in the Indoms section have the following format:
The entries in the Instances section have the following format:
The entries in the Metrics section have the following format:
The entries in the Values section have the following format:
Each entry in the strings section is a 256 byte character array, containing a single NULL-terminated character string. So each string has a maximum length of 256 bytes, which includes the terminating NULL.