kstat - kernel statistics structure
illumos DDI specific (illumos DDI)
Each kernel statistic (kstat) exported by device drivers consists of a
header section and a data section. The kstat structure is the header
portion of the statistic.
A driver receives a pointer to a kstat structure from a
successful call to kstat_create(9F). Drivers should never allocate a
kstat structure in any other manner.
After allocation, the driver should perform any further
initialization needed before calling kstat_install(9F) to actually
export the kstat.
void *ks_data; /* kstat type-specif. data */
ulong_t ks_ndata; /* # of type-specif. data
ulong_t ks_data_size; /* total size of kstat data
int (*ks_update)(struct kstat *, int);
void *ks_private; /* arbitrary provider-private
void *ks_lock; /* protects kstat's data */
The members of the kstat structure available to examine or
set by a driver are as follows:
Points to the data portion of the kstat
allocated by kstat_create(9F)
for the drivers use, or by the driver if
it is using virtual kstat
The number of data records in this kstat
. Set by
The amount of data pointed to by ks_data
. Set by
Pointer to a routine that dynamically updates
. This is useful for drivers where the underlying device keeps
cheap hardware statistics, but where extraction is expensive. Instead of
constantly keeping the kstat
data section up to date, the driver can
supply a ks_update(9E)
function that updates the kstat
section on demand. To take advantage of this feature, set the ks_update
field before calling kstat_install(9F)
Is a private field for the driver's use. Often used in
Is a pointer to a mutex that protects this kstat.
kstat data sections are optionally protected by the per-kstat
ks_lock. If ks_lock is non-NULL, kstat clients
(such as /dev/kstat) will acquire this lock for all of their operations
on that kstat. It is up to the kstat provider to decide whether
guaranteeing consistent data to kstat clients is sufficiently important
to justify the locking cost. Note, however, that most statistic updates
already occur under one of the provider's mutexes. If the provider sets
ks_lock to point to that mutex, then kstat data locking is free.
ks_lock is really of type (kmutex_t*) and is declared as
(void*) in the kstat header. That way, users do not have to be
exposed to all of the kernel's lock-related data structures.