---

mmv_stats_init(3) — Linux manual page

MMV_STATS_INIT(3) Library Functions Manual MMV_STATS_INIT(3)

NAME top

 mmv_stats_init, mmv_stats2_init - create and initialize Memory
 Mapped Value file

C SYNOPSIS top

 #include <pcp/pmapi.h>
 #include <pcp/mmv_stats.h>
 void *mmv_stats_init(const char *name, int cluster,
 mmv_stats_flags_t flags,
 const mmv_metric_t *stats, int nstats,
 mmv_indom_t *indoms, int nindoms);
 void *mmv_stats2_init(const char *name, int cluster,
 mmv_stats_flags_t flags,
 const mmv_metric2_t *stats2, int nstats2,
 mmv_indom2_t *indoms2, int nindoms2);
 cc ... -lpcp_mmv -lpcp

DESCRIPTION top

 Note: these functions are deprecated - see mmv_stats_registry(3).
 mmv_stats_init creates and initializes the content of the MMV(5)
 file, returning a handle that is used in subsequent MMV API calls.
 mmv_stats2_init is equivalent to mmv_stats_init except that it
 provides an option for longer metric and instance names.
 mmv_stats_stop performs an orderly shutdown of the mapping handle
 returned by an earlier initialization call.
 The file is created in the $PCP_TMP_DIR/mmv directory, name argu‐
 ment is expected to be a basename of the file, not the full path.
 The metadata content of the file does not change after the file
 has been created.
 The old file is removed unconditionally unless there was an error.
 cluster is the preferred MMV PMDA cluster ID to be used for the
 metrics originating from this call to mmv_stats_init. The flags
 provide additional control over the behaviour of the MMV PMDA -
 e.g. use of MMV_FLAG_PROCESS will ensure values are only exported
 when the instrumented application is running - this is verified on
 each request for new values.
 stats is the array of mmv_metric_t elements of length nstats. Each
 element of the array describes one PCP metric.
 typedef struct {
 char name[MMV_NAMEMAX]; /* Name of the metric */
 __uint32_t item; /* Item component of PMID */
 mmv_metric_type_t type; /* Type of the metric */
 mmv_metric_sem_t semantics; /* Semantics of the metric */
 pmUnits dimension; /* Dimensions (TIME,SPACE,etc) */
 __uint32_t indom; /* Instance domain identifier */
 char *shorttext; /* Optional, one-line help */
 char *helptext; /* Optional, full help text */
 } mmv_metric_t;
 stats2 is the array of mmv_metric2_t elements of length nstats2.
 Each element of the array describes one PCP metric, the only dif‐
 ference to stats is the lifting of the restriction on name length
 (previously MMV_NAMEMAX, which is 64 bytes).
 typedef struct {
 char *name; /* Name of the metric */
 __uint32_t item; /* Item component of PMID */
 mmv_metric_type_t type; /* Type of the metric */
 mmv_metric_sem_t semantics; /* Semantics of the metric */
 pmUnits dimension; /* Dimensions (TIME,SPACE,etc) */
 __uint32_t indom; /* Instance domain identifier */
 char *shorttext; /* Optional, one-line help */
 char *helptext; /* Optional, full help text */
 } mmv_metric2_t;
 If indom is not zero and not PM_INDOM_NULL, then the metric has
 multiple values and there must be a corresponding indom entry in
 the indom list (uniquely identified by serial number).
 The stats and stats2 arrays cannot contain any elements which have
 no name - this is considered an error and no metrics will be ex‐
 ported in this case.
 indoms is the array of mmv_indom_t elements of length nindoms.
 Each element of the array describes one PCP instance domain.
 typedef struct {
 __int32_t internal;
 char external[MMV_NAMEMAX];
 } mmv_instances_t;
 typedef struct {
 __uint32_t serial; /* Unique serial number */
 __uint32_t count; /* Number of instances */
 mmv_instances_t *instances; /* Internal/external IDs */
 char *shorttext; /* Short help text */
 char *helptext; /* Long help text */
 } mmv_indom_t;
 indoms2 is the array of mmv_indom2_t elements of length nindoms2.
 Each element of the array describes one PCP instance domain, and
 the only difference to indoms is the lifting of the restriction on
 external instance name lengths (previously MMV_NAMEMAX, which is
 64 bytes).
 typedef struct {
 __int32_t internal;
 char *external;
 } mmv_instances2_t;
 typedef struct {
 __uint32_t serial; /* Unique serial number */
 __uint32_t count; /* Number of instances */
 mmv_instances2_t *instances; /* Internal/external IDs */
 char *shorttext; /* Short help text */
 char *helptext; /* Long help text */
 } mmv_indom2_t;

RETURN VALUES top

 These functions return the address of the memory mapped region on
 success. On failure, NULL is returned and errno  is set to a value
 suitable for decoding with strerror(3).

SEE ALSO top

 mmv_stats_registry(3), mmv_lookup_value_desc(3), mmv_inc_value(3),
 strerror(3) and mmv(5).

COLOPHON top

 This page is part of the PCP (Performance Co-Pilot) project. In‐
 formation about the project can be found at ⟨http://www.pcp.io/⟩.
 If you have a bug report for this manual page, send it to
 pcp@groups.io. This page was obtained from the project's upstream
 Git repository ⟨https://github.com/performancecopilot/pcp.git⟩ on
 2025年08月11日. (At that time, the date of the most recent commit
 that was found in the repository was 2025年08月11日.) 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 man-pages@man7.org
Performance Co-Pilot MMV_STATS_INIT(3)

---

Pages that refer to this page: pmdammv(1), mmv_inc_value(3), mmv_lookup_value_desc(3), mmv_set_value(3)

---

---

---