Provided by: libpcp-mmv1-dev_3.5.6ubuntu1_i386 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).