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Kernel Statistics Library Functions                              kstat(3KSTAT)

       kstat - obsolete kernel statistics facility

       The  kstat facility is a general-purpose mechanism for providing kernel
       statistics to users.

   The kstat model
       The kernel maintains a linked list of statistics structures, or kstats.
       Each  kstat  has  a common header section and a type-specific data sec‐
       tion. The header section is defined by the kstat_t structure:

   kstat header
         typedef   int kid_t;    /* unique kstat id */

         typedef struct kstat {
             * Fields relevant to both kernel and user
            hrtime_t      ks_crtime;               /* creation time */
            struct kstat  *ks_next;                /* kstat chain linkage */
            kid_t         ks_kid;                  /* unique kstat ID */
            char          ks_module[KSTAT_STRLEN]; /* module name */
            uchar_t       ks_resv;                 /* reserved */
            int           ks_instance;             /* module's instance */
            char          ks_name[KSTAT_STRLEN];   /* kstat name */
            uchar_t       ks_type;                 /* kstat data type */
            char          ks_class[KSTAT_STRLEN];  /* kstat class */
            uchar_t       ks_flags;                /* kstat flags */
            void          *ks_data;                /* kstat type-specific
                                                      data */
            uint_t        ks_ndata;                /* # of data records */
            size_t        ks_data_size;            /* size of kstat data
                                                      section */
            hrtime_t      ks_snaptime;             /* time of last data
                                                      snapshot */

             * Fields relevant to kernel only
            int(*ks_update)(struct kstat *, int);
            void  *ks_private;
            int(*ks_snapshot)(struct kstat *, void *, int);
            void  *ks_lock;
         } kstat_t;

       The fields that are of significance to the user are:

       ks_crtime       The time the kstat was created. This allows you to com‐
                       pute  the rates of various counters since the kstat was
                       created; "rate since boot" is replaced by the more gen‐
                       eral  concept of "rate since kstat creation". All times
                       associated with kstats (such  as  creation  time,  last
                       snapshot time, kstat_timer_t and kstat_io_t timestamps,
                       and the like) are 64-bit nanosecond values.  The  accu‐
                       racy  of kstat timestamps is machine dependent, but the
                       precision (units) is the same across all platforms. See
                       gethrtime(3C)  for general information about high-reso‐
                       lution timestamps.

       ks_next         kstats are stored as a linked list, or  chain.  ks_next
                       points to the next kstat in the chain.

       ks_kid          A unique identifier for the kstat.

       ks_module,      contain  the  name and instance of the module that cre‐
       ks_instance     ated the kstat. In cases where there can  only  be  one
                       instance, ks_instance is 0.

       ks_name         gives  a  meaningful  name  to  a kstat. The full kstat
                       namespace is  <ks_module,ks_instance,ks_name>,  so  the
                       name only need be unique within a module.

       ks_type         The  type  of  data in this kstat. kstat data types are
                       discussed below.

       ks_class        Each kstat can be characterized as  belonging  to  some
                       broad class of statistics, such as disk, tape, net, vm,
                       and streams. This field can be  used  as  a  filter  to
                       extract  related  kstats. The following values are cur‐
                       rently in use: disk, tape, controller,  net,  rpc,  vm,
                       kvm,  hat,  streams, kmem, kmem_cache, kstat, and misc.
                       (The kstat class encompasses things like kstat_types.)

       ks_data,        ks_data is a pointer to the kstat's data  section.  The
       ks_ndata,       type  of data stored there depends on ks_type. ks_ndata
       ks_data_size    indicates the number of data records. Only  some  kstat
                       types   support   multiple   data  records.  Currently,
                       kstats  support  multiple data records. KSTAT_TYPE_INTR
                       and KSTAT_TYPE_IO kstats support only one data  record.
                       ks_data_size  is the total size of the data section, in

       ks_snaptime     The timestamp for the last data snapshot.  This  allows
                       you to compute activity rates:

                       rate  =  (new_count  -  old_count)  /  (new_snaptime  -

   kstat data types
       The following types of kstats are currently available:

         #define KSTAT_TYPE_RAW    0   /* can be anything */
         #define KSTAT_TYPE_NAMED  1   /* name/value pairs */
         #define KSTAT_TYPE_INTR   2   /* interrupt statistics */
         #define KSTAT_TYPE_IO     3   /* I/O statistics */
         #define KSTAT_TYPE_TIMER  4   /* event timers */

       To get a list of all kstat types currently  supported  in  the  system,
       tools  can  read  out  the standard system kstat kstat_types (full name
       spec is <"unix", 0, "kstat_types">). This is a  KSTAT_TYPE_NAMED  kstat
       in  which  the  name  field  describes the type of kstat, and the value
       field is the kstat type number (for example, KSTAT_TYPE_IO is type 3 --
       see above).

   Raw kstat
       KSTAT_TYPE_RAW    raw data

       The "raw" kstat type is just treated as an array of bytes. This is gen‐
       erally used to export well-known structures, like sysinfo.

   Name=value kstat
       KSTAT_TYPE_NAMED    A list of arbitrary name=value statistics.

         typedef struct kstat_named {
            char    name[KSTAT_STRLEN];    /* name of counter */
            uchar_t data_type;             /* data type */
            union {
                     charc[16];            /* enough for 128-bit ints */
                     struct {
                        union {
                            char *ptr;    /* NULL-terminated string */
                        } addr;
                        uint32_t len;     /* length of string */
                     } str;
                     int32_t   i32;
                     uint32_t  ui32;
                     int64_t   i64;
                     uint64_t  ui64;

           /* These structure members are obsolete */

                     int32_t   l;
                     uint32_t  ul;
                     int64_t   ll;
                     uint64_t  ull;
                  } value;                /* value of counter */
         } kstat_named_t;

         /* The following types are Committed


         /* The following types are Obsolete */


       Some devices need to publish strings that exceed the maximum value  for
       KSTAT_DATA_CHAR in length; KSTAT_DATA_STRING is a data type that allows
       arbitrary-length strings to be  associated  with  a  named  kstat.  The
       macros  below are the supported means to read the pointer to the string
       and its length.

         #define KSTAT_NAMED_STR_PTR(knptr) ((knptr)->value.str.addr.ptr)
         #define KSTAT_NAMED_STR_BUFLEN(knptr) ((knptr)->value.str.len)

       KSTAT_NAMED_STR_BUFLEN() returns the number of bytes required to  store
       the    string   pointed   to   by   KSTAT_NAMED_STR_PTR();   that   is,
       strlen(KSTAT_NAMED_STR_PTR()) + 1.

   Interrupt kstat
       KSTAT_TYPE_INTR    Interrupt statistics.

       An interrupt is a hard interrupt  (sourced  from  the  hardware  device
       itself),  a  soft  interrupt (induced by the system via the use of some
       system interrupt source), a watchdog interrupt (induced by  a  periodic
       timer  call),  spurious (an interrupt entry point was entered but there
       was no interrupt to service), or multiple  service  (an  interrupt  was
       detected  and  serviced  just  prior to returning from any of the other

         #define KSTAT_INTR_HARD      0
         #define KSTAT_INTR_SOFT      1
         #define KSTAT_INTR_WATCHDOG  2
         #define KSTAT_INTR_SPURIOUS  3
         #define KSTAT_INTR_MULTSVC   4
         #define KSTAT_NUM_INTRS      5

         typedef struct kstat_intr {
            uint_t intrs[KSTAT_NUM_INTRS]; /* interrupt counters */
         } kstat_intr_t;

   Event timer kstat
       KSTAT_TYPE_TIMER    Event timer statistics.

       These provide basic counting and timing information  for  any  type  of

         typedef struct kstat_timer {
            char         name[KSTAT_STRLEN]; /* event name */
            uchar_t      resv;               /* reserved */
            u_longlong_t num_events;         /* number of events */
            hrtime_t     elapsed_time;       /* cumulative elapsed time */
            hrtime_t     min_time;           /* shortest event duration */
            hrtime_t     max_time;           /* longest event duration */
            hrtime_t     start_time;         /* previous event start time */
            hrtime_t     stop_time;          /* previous event stop time */
         } kstat_timer_t;

   I/O kstat
       KSTAT_TYPE_IO    I/O statistics.

         typedef struct kstat_io {
          * Basic counters.
         u_longlong_t     nread;      /* number of bytes read */
         u_longlong_t     nwritten;   /* number of bytes written */
         uint_t           reads;      /* number of read operations */
         uint_t           writes;     /* number of write operations */
         * Accumulated time and queue length statistics.
         * Time statistics are kept as a running sum of "active" time.
         * Queue length statistics are kept as a running sum of the
         * product of queue length and elapsed time at that length --
         * that is, a Riemann sum for queue length integrated against time.
         *               ^
         *               |                       _________
         *               8                       | i4    |
         *               |                       |       |
         *       Queue   6                       |       |
         *       Length  |       _________       |       |
         *               4       | i2    |_______|       |
         *               |       |       i3              |
         *               2_______|                       |
         *               |    i1                         |
         *               |_______________________________|
         *               Time->  t1      t2      t3      t4
         * At each change of state (entry or exit from the queue),
         * we add the elapsed time (since the previous state change)
         * to the active time if the queue length was non-zero during
         * that interval; and we add the product of the elapsed time
         * times the queue length to the running length*time sum.
         * This method is generalizable to measuring residency
         * in any defined system: instead of queue lengths, think
         * of "outstanding RPC calls to server X".
         * A large number of I/O subsystems have at least two basic
         * "lists" of transactions they manage: one for transactions
         * that have been accepted for processing but for which processing
         * has yet to begin, and one for transactions which are actively
         * being processed (but not done). For this reason, two cumulative
         * time statistics are defined here: pre-service (wait) time,
         * and service (run) time.
         * The units of cumulative busy time are accumulated nanoseconds.
         * The units of cumulative length*time products are elapsed time
         * times queue length.
         hrtime_t   wtime;            /* cumulative wait (pre-service) time */
         hrtime_t   wlentime;         /* cumulative wait length*time product*/
         hrtime_t   wlastupdate;      /* last time wait queue changed */
         hrtime_t   rtime;            /* cumulative run (service) time */
         hrtime_t   rlentime;         /* cumulative run length*time product */
         hrtime_t   rlastupdate;      /* last time run queue changed */
         uint_t     wcnt;             /* count of elements in wait state */
         uint_t     rcnt;             /* count of elements in run state */
         } kstat_io_t;

   Using libkstat
       The  kstat  library,  libkstat, defines the user interface (API) to the
       system's kstat facility.

       You begin by opening libkstat with kstat_open(3KSTAT), which returns  a
       pointer  to  a  fully initialized kstat control structure. This is your
       ticket to subsequent libkstat operations:

         typedef struct kstat_ctl {
            kid_t     kc_chain_id;    /* current kstat chain ID */
            kstat_t   *kc_chain;      /* pointer to kstat chain */
            int       kc_kd;          /* /dev/kstat descriptor */
         } kstat_ctl_t;

       Only the first two fields, kc_chain_id and kc_chain, are of interest to
       libkstat  clients.  (kc_kd is the descriptor for /dev/kstat, the kernel
       statistics driver. libkstat functions are built on  top  of  /dev/kstat
       ioctl(2)  primitives.  Direct  interaction  with /dev/kstat is strongly
       discouraged, since it is not a public interface.)

       kc_chain points to your copy of the kstat chain. You typically walk the
       chain to find and process a certain kind of kstat. For example, to dis‐
       play all I/O kstats:

         kstat_ctl_t    *kc;
         kstat_t        *ksp;
         kstat_io_t     kio;

         kc = kstat_open();
         for (ksp = kc->kc_chain; ksp != NULL; ksp = ksp->ks_next) {
                 if (ksp->ks_type == KSTAT_TYPE_IO) {
                       kstat_read(kc, ksp, &kio);

       kc_chain_id is the kstat chain ID, or KCID, of your copy of  the  kstat
       chain. See kstat_chain_update(3KSTAT) for an explanation of KCIDs.

       /dev/kstat                  kernel statistics driver

       /usr/include/kstat.h        header

       /usr/include/sys/kstat.h    header

       ioctl(2),  gethrtime(3C),  getloadavg(3C),  kstat_chain_update(3KSTAT),
       kstat_close(3KSTAT),  kstat_data_lookup(3KSTAT),  kstat_lookup(3KSTAT),
       kstat_open(3KSTAT),       kstat_read(3KSTAT),      kstat_write(3KSTAT),
       attributes(7),          kstat2(3KSTAT2),          kstat2_open(3KSTAT2),
       kstat2_lookup_map(3KSTAT2),                    kstat2_map_get(3KSTAT2),
       kstat2_update(3KSTAT2), kstat2_close(3KSTAT2)

       The facility described in  this  document  is  deprecated  and  may  be
       removed  in  a future release of Oracle Solaris. Use the kstat2() func‐
       tion instead. For more information, see the kstat2(3KSTAT2) man page.

Oracle Solaris 11.4               02 Feb 2017                    kstat(3KSTAT)
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