Provided by: libpcp-mmv1-dev_3.5.11_amd64 bug

NAME

       mmv - Memory Mapped Values for Performance Co-Pilot

SYNOPSIS

       $PCP_TMP_DIR/mmv/<file>

DESCRIPTION

       The  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 FORMAT

       Each file starts with the following header:

                              ┌───────┬────────┬──────────────────────────┐
                              │Offset │ Length │           Name           │
                              ├───────┼────────┼──────────────────────────┤
                              │   0   │   4    │ tag == "MMV\0"           │
                              ├───────┼────────┼──────────────────────────┤
                              │   4   │   4    │ Version                  │
                              ├───────┼────────┼──────────────────────────┤
                              │   8   │   8    │ Generation 1             │
                              ├───────┼────────┼──────────────────────────┤
                              │  16   │   8    │ Generation 2             │
                              ├───────┼────────┼──────────────────────────┤
                              │  24   │   4    │ Number of TOC entries    │
                              ├───────┼────────┼──────────────────────────┤
                              │  28   │   4    │ Flags                    │
                              ├───────┼────────┼──────────────────────────┤
                              │  32   │   4    │ Process identifier (PID) │
                              ├───────┼────────┼──────────────────────────┤
                              │  36   │   4    │ Cluster identifier       │
                              └───────┴────────┴──────────────────────────┘
       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:

                    ┌───────┬────────┬─────────────────────────────────────────────┐
                    │Offset │ Length │                    Value                    │
                    ├───────┼────────┼─────────────────────────────────────────────┤
                    │  0    │   4    │ Section Type (see mmv_stats.h)              │
                    ├───────┼────────┼─────────────────────────────────────────────┤
                    │  4    │   4    │ Number of entries in the section            │
                    ├───────┼────────┼─────────────────────────────────────────────┤
                    │  8    │   8    │ Section's offset from the start of the file │
                    └───────┴────────┴─────────────────────────────────────────────┘
       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:

                        ┌───────┬────────┬──────────────────────────────────────┐
                        │Offset │ Length │                Value                 │
                        ├───────┼────────┼──────────────────────────────────────┤
                        │   0   │   4    │ Unique serial number for this domain │
                        ├───────┼────────┼──────────────────────────────────────┤
                        │   4   │   4    │ Number of entries in the domain      │
                        ├───────┼────────┼──────────────────────────────────────┤
                        │   8   │   8    │ Offset to first instance             │
                        ├───────┼────────┼──────────────────────────────────────┤
                        │  16   │   8    │ Short help text offset               │
                        ├───────┼────────┼──────────────────────────────────────┤
                        │  24   │   8    │ Long help text offset                │
                        └───────┴────────┴──────────────────────────────────────┘
       The entries in the Instances section have the following format:

                           ┌───────┬────────┬───────────────────────────────┐
                           │Offset │ Length │             Value             │
                           ├───────┼────────┼───────────────────────────────┤
                           │   0   │    8   │ Offset into the indom section │
                           ├───────┼────────┼───────────────────────────────┤
                           │   8   │    4   │ Unused padding (zero filled)  │
                           ├───────┼────────┼───────────────────────────────┤
                           │  12   │    4   │ Internal instance identifier  │
                           ├───────┼────────┼───────────────────────────────┤
                           │  16   │   64   │ External instance identifier  │
                           └───────┴────────┴───────────────────────────────┘
       The entries in the Metrics section have the following format:

                           ┌───────┬────────┬───────────────────────────────┐
                           │Offset │ Length │             Value             │
                           ├───────┼────────┼───────────────────────────────┤
                           │   0   │   64   │ Metric Name                   │
                           ├───────┼────────┼───────────────────────────────┤
                           │  64   │    4   │ Metric Item (see PMDA(3))     │
                           ├───────┼────────┼───────────────────────────────┤
                           │  68   │    4   │ Metric Type (see mmv_stats.h) │
                           ├───────┼────────┼───────────────────────────────┤
                           │  72   │    4   │ Semantics (see PMAPI(3))      │
                           ├───────┼────────┼───────────────────────────────┤
                           │  76   │    4   │ Dimensions (see PMAPI(3))     │
                           ├───────┼────────┼───────────────────────────────┤
                           │  80   │    4   │ Instance Domain ID            │
                           ├───────┼────────┼───────────────────────────────┤
                           │  84   │    4   │ Unused padding (zero filled)  │
                           ├───────┼────────┼───────────────────────────────┤
                           │  88   │    8   │ Short help text offset        │
                           ├───────┼────────┼───────────────────────────────┤
                           │  96   │    8   │ Long help text offset         │
                           └───────┴────────┴───────────────────────────────┘
       The entries in the Values section have the following format:

                         ┌───────┬────────┬────────────────────────────────────┐
                         │Offset │ Length │               Value                │
                         ├───────┼────────┼────────────────────────────────────┤
                         │   0   │   8    │ pmAtomValue (see PMAPI(3))         │
                         ├───────┼────────┼────────────────────────────────────┤
                         │   8   │   8    │ Extra space for STRING and ELAPSED │
                         ├───────┼────────┼────────────────────────────────────┤
                         │  16   │   8    │ Offset into the Metrics section    │
                         ├───────┼────────┼────────────────────────────────────┤
                         │  24   │   8    │ Offset into the Instances section  │
                         └───────┴────────┴────────────────────────────────────┘
       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.

SEE ALSO

       PCPIntro(1), PMAPI(3), mmv_stats_init(3), pcp.conf(4) and pcp.env(4).