kstat_queue, kstat_waitq_enter, kstat_waitq_exit, kstat_runq_enter,
kstat_runq_exit, kstat_waitq_to_runq, kstat_runq_back_to_waitq - update
I/O kstat statistics
void kstat_waitq_enter(kstat_io_t *kiop);
void kstat_waitq_exit(kstat_io_t *kiop);
void kstat_runq_enter(kstat_io_t *kiop);
void kstat_runq_exit(kstat_io_t *kiop);
void kstat_waitq_to_runq(kstat_io_t *kiop);
void kstat_runq_back_to_waitq(kstat_io_t *kiop);
Solaris DDI specific (Solaris DDI)
Pointer to a kstat_io(9S) structure.
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 kstat_queue() family of functions manage these times based on the
transitions between the driver wait queue and run queue.
kstat_waitq_enter()kstat_waitq_enter() should be called when
a request arrives and is placed into a
pre-service state (such as just prior to
kstat_waitq_exit()kstat_waitq_exit() should be used when a
request is removed from its pre-service
state. (such as just prior to calling the
driver's start routine).
kstat_runq_enter()kstat_runq_enter() is also called when a
request is placed in its service state
(just prior to calling the driver's start
routine, but after kstat_waitq_exit()).
kstat_runq_exit()kstat_runq_exit() is used when a request
is removed from its service state (just
prior to calling biodone(9F)).
kstat_waitq_to_runq()kstat_waitq_to_runq() transitions a
request from the wait queue to the run
queue. This is useful wherever the driver
would have normally done a
kstat_waitq_exit() followed by a call to
kstat_runq_back_to_waitq()kstat_runq_back_to_waitq() transitions a
request from the run queue back to the
wait queue. This may be necessary in some
cases (write throttling is an example).
CONTEXTkstat_create() can be called from user or kernel context.
These transitions must be protected by holding the kstat's ks_lock, and
must be completely accurate (all transitions are recorded). Forgetting
a transition may, for example, make an idle disk appear 100% busy.
SEE ALSObiodone(9F), disksort(9F), kstat_create(9F), kstat_delete(9F),
kstat_named_init(9F), kstat(9S), kstat_io(9S)
Writing Device Drivers
Apr 4, 1994 KSTAT_QUEUE(9F)