Kernel Functions for Drivers                      kstatqueue(9F)



NAME
     kstatqueue,      kstatwaitqenter,       kstatwaitqexit,
     kstatrunqenter,    kstatrunqexit,   kstatwaitqtorunq,
     kstatrunqbacktowaitq - update I/O kstat statistics

SYNOPSIS
     #include 
     #include 



     void kstatwaitqenter(kstatiot *kiop);


     void kstatwaitqexit(kstatiot *kiop);


     void kstatrunqenter(kstatiot *kiop);


     void kstatrunqexit(kstatiot *kiop);


     void kstatwaitqtorunq(kstatiot *kiop);


     void kstatrunqbacktowaitq(kstatiot *kiop);


INTERFACE LEVEL
     Solaris DI specific (Solaris DI)

PARAMETERS
     kiop     Pointer to a kstatio(9S) structure.


DESCRIPTION
     A large number of I/O subsystems have  at  least  two  basic
     "lists"  (or  queues)  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 kept: wait (pre-
     service) time, and run (service) time.


     The kstatqueue() family of  functions  manage  these  times
     based  on  the transitions between the driver wait queue and
     run queue.

     kstatwaitqenter()           kstatwaitqenter() should  be
                                   called  when a request arrives



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Kernel Functions for Drivers                      kstatqueue(9F)



                                   and  is  placed  into  a  pre-
                                   service  state  (such  as just
                                   prior        to        calling
                                   disksort(9F)).


     kstatwaitqexit()            kstatwaitqexit()  should  be
                                   used when a request is removed
                                   from  its  pre-service  state.
                                   (such as just prior to calling
                                   the driver's start routine).


     kstatrunqenter()            kstatrunqenter()   is   also
                                   called   when   a  request  is
                                   placed in  its  service  state
                                   (just  prior  to  calling  the
                                   driver's  start  routine,  but
                                   after kstatwaitqexit()).


     kstatrunqexit()             kstatrunqexit() is used when
                                   a  request is removed from its
                                   service state (just  prior  to
                                   calling biodone(9F)).


     kstatwaitqtorunq()         kstatwaitqtorunq()  transi-
                                   tions  a request from the wait
                                   queue to the run  queue.  This
                                   is  useful wherever the driver
                                   would  have  normally  done  a
                                   kstatwaitqexit() followed by
                                   a call to kstatrunqenter().


     kstatrunqbacktowaitq()    kstatrunqbacktowaitq()
                                   transitions a request from the
                                   run queue  back  to  the  wait
                                   queue.  This  may be necessary
                                   in some  cases  (write  throt-
                                   tling is an example).


RETURN VALUES
     None.

CONTEXT
     kstatcreate() can be called from user or kernel context.

WARNINGS




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Kernel Functions for Drivers                      kstatqueue(9F)



     These transitions must be protected by holding  the  kstat's
     kslock,  and  must  be completely accurate (all transitions
     are recorded). Forgetting a  transition  may,  for  example,
     make an idle disk appear 100% busy.

SEE ALSO
     biodone(9F),         disksort(9F),         kstatcreate(9F),
     kstatdelete(9F),      kstatnamedinit(9F),      kstat(9S),
     kstatio(9S)


     Writing Device Drivers











































SunOS 5.11           Last change: 4 Apr 1994                    3