disksort(9f) [opensolaris man page]

disksort(9F)						   Kernel Functions for Drivers 					      disksort(9F)

NAME

       disksort - single direction elevator seek sort for buffers

SYNOPSIS

       #include <sys/conf.h>
       #include <sys/ddi.h>
       #include <sys/sunddi.h>
       void

       disksort(struct diskhd *dp, struct buf *bp);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI).

PARAMETERS

       dp    A	pointer  to  a diskhd structure. A diskhd structure is essentially identical to head of a buffer structure (see buf(9S)). The only
	     defined items of interest for this structure are the av_forw and av_back structure elements which are used to maintain the front  and
	     tail pointers of the forward linked I/O request queue.

       bp    A	pointer  to  a	buffer	structure.  Typically this is the I/O request that the driver receives in its strategy routine (see strat-
	     egy(9E)). The driver is responsible for initializing the b_resid structure element to a meaningful sort key value	prior  to  calling
	     disksort().

DESCRIPTION

       The function disksort() sorts a pointer to a buffer into a single forward linked list headed by the av_forw element of the argument *dp.

       It  uses a one-way elevator algorithm that sorts buffers into the queue in ascending order based upon a key value held in the argument buf-
       fer structure element b_resid.

       This value can either be the driver calculated cylinder number for the I/O request described by the buffer argument, or simply the absolute
       logical	block  for  the  I/O  request, depending on how fine grained the sort is desired to be or how applicable either quantity is to the
       device in question.

       The head of the linked list is found by use of the av_forw structure element of the argument *dp. The tail of the linked list is  found	by
       use  of	the  av_back  structure element of the argument *dp. The av_forw element of the *bp argument is used by disksort() to maintain the
       forward linkage. The value at the head of the list presumably indicates the currently active disk area.

CONTEXT

       This function can be called from user, interrupt, or kernel context.

SEE ALSO

       strategy(9E), buf(9S)

       Writing Device Drivers

WARNINGS

       The disksort() function does no locking. Therefore, any locking is completely the responsibility of the caller.

SunOS 5.11							    16 Jan 2006 						      disksort(9F)

kstat_queue(9F) 					   Kernel Functions for Drivers 					   kstat_queue(9F)

NAME

       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

SYNOPSIS

       #include <sys/types.h>
       #include <sys/kstat.h>

       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);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI)

PARAMETERS

       kiop	       Pointer to a kstat_io(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 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  calling
	   disksort(9F)).

       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 nor-
	   mally done a kstat_waitq_exit() followed by a call to kstat_runq_enter().

       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).

RETURN VALUES

       None.

CONTEXT

       kstat_create() can be called from user or kernel context.

WARNINGS

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

SEE ALSO

       biodone(9F), disksort(9F), kstat_create(9F), kstat_delete(9F), kstat_named_init(9F), kstat(9S), kstat_io(9S)

       Writing Device Drivers

SunOS 5.10							    4 Apr 1994							   kstat_queue(9F)