Return to kstat.4 CVS log

Up to [local] / src / share / man / man4

get the list of things in the full identifier right.

.\"	$OpenBSD: kstat.4,v 1.8 2022/01/14 04:25:57 dlg Exp $
.\"
.\" Copyright (c) 2022 Jonathan Gray <jsg@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: January 14 2022 $
.Dt KSTAT 4
.Os
.Sh NAME
.Nm kstat
.Nd kernel statistics
.Sh SYNOPSIS
.Cd "pseudo-device kstat"
.Sh DESCRIPTION
The
.Pa /dev/kstat
device exposes kernel statistics (kstats) to userland.
.Sh IOCTLS
The kstat
.Xr ioctl 2
calls are provided in
.In sys/kstat.h .
.Pp
With the exception of
.Dv KSTATIOC_VERSION ,
the kstat
.Xr ioctl 2
calls use the
.Vt kstat_req
structure to request or enumerate kernel
statistic data from the kernel:
.Bd -literal
struct kstat_req {
	unsigned int		 ks_rflags;
#define KSTATIOC_F_IGNVER		(1 << 0)
	/* the current version of the kstat subsystem */
	unsigned int		 ks_version;

	uint64_t		 ks_id;

	char			 ks_provider[KSTAT_STRLEN];
	unsigned int		 ks_instance;
	char			 ks_name[KSTAT_STRLEN];
	unsigned int		 ks_unit;

	struct timespec		 ks_created;
	struct timespec		 ks_updated;
	struct timespec		 ks_interval;
	unsigned int		 ks_type;
	unsigned int		 ks_state;

	void			*ks_data;
	size_t			 ks_datalen;
	unsigned int		 ks_dataver;
};
.Ed
.Pp
The kstat subsystem increments a version number when a kstat is added to or
removed from the subsystem so changes to the set of kstats can be detected.
The current version can be requested with a
.Dv KSTATIOC_VERSION
.Xr ioctl 2
call.
Programs requesting a kstat with the other
.Xr ioctl 2
calls pass the current version in
.Va ks_version ,
and if the version differs an error will be returned with
.Xr errno 2
set to
.Dv EINVAL
to indicate that the program should resynchronise with the kernel
subsystem.
This check can be disabled by setting the
.Dv KSTATIOC_F_IGNVER
flag in
.Va ks_rflags .
.Pp
A kstat is identified by a 64bit number, or the combination of a
provider name, instance number, name, and unit number.
.Pp
Unless
.Va ks_data
is
.Dv NULL ,
the kstat subsystem will request an update of the statistics data
and copy up to
.Va ks_datalen
bytes of it to the specified memory.
.Pp
The kstat
.Xr ioctl 2
calls are as follows:
.Bl -tag -width Ds
.It Dv KSTATIOC_VERSION Fa "unsigned int"
Get the current version of the set of kernel statistics.
.It Dv KSTATIOC_FIND_ID Fa "struct kstat_req"
Request the kstat identified by
.Va ks_id .
.It Dv KSTATIOC_NFIND_ID Fa "struct kstat_req"
Request a kstat with an identifier greater than or equal to
.Va ks_id .
.It Dv KSTATIOC_FIND_PROVIDER Fa "struct kstat_req"
Request the kstat identified by
.Va ks_provider ,
.Va ks_instance ,
.Va ks_name ,
and
.Va ks_unit .
.It Dv KSTATIOC_NFIND_PROVIDER Fa "struct kstat_req"
Request the kstat or next kstat from the set of kstats ordered by
.Va ks_provider ,
.Va ks_instance ,
.Va ks_name ,
and
.Va ks_unit .
.It Dv KSTATIOC_FIND_NAME Fa "struct kstat_req"
Request the kstat identified by
.Va ks_name ,
.Va ks_unit ,
.Va ks_provider ,
and
.Va ks_instance .
.It Dv KSTATIOC_NFIND_NAME Fa "struct kstat_req"
Request the kstat or next kstat from the set of kstats ordered by
.Va ks_name ,
.Va ks_unit ,
.Va ks_provider ,
and
.Va ks_instance .
.El
.Pp
Upon the successful request of a kstat, the
.Nm
driver will update the
.Vt kstat_req
structure with current information about that kstat.
Updated fields include:
.Bl -tag -width Ds
.It Va ks_version
The current version of the kstat subsystem.
.It Va ks_id
The 64bit unique identifier for the requested kstat.
A kstat can be requested using this identifier and the
.Dv KSTATIOC_FIND_ID
.Xr ioctl 2
call.
.It Va ks_provider , Va ks_instance , Va ks_name , Va ks_unit
The fully specified identifier of the kstat.
A kstat can be requested using these identifiers with the
.Dv KSTATIOC_FIND_NAME
and
.Dv KSTATIOC_FIND_PROVIDER
.Xr ioctl 2
calls.
Groups of kstats with the same identifier or name can be enumerated
or requested with the
.Dv KSTATIOC_NFIND_NAME
and
.Dv KSTATIOC_NFIND_PROVIDER
.Xr ioctl 2
calls without having to fetch the entire set of kstats and filtering
them.
.It Va ks_created
The system uptime when the kstat was created and added to the kstat
subsystem.
.It Va ks_updated
The system uptime at which the kstat data payload was last updated.
A kstat provider may update data when requested, or report when
data was last updated by some other process.
.Va ks_updated
can by used by a program to identify if data has been updated, or
for calculating rates of changes of values between updates.
.It Va ks_type
The type or structure of the data payload.
Currently supported types are documented in
.Xr kstat_create 9 .
.\" .It Va ks_state
.\" The state of the kstat. create or installed iirc
.It Va ks_datalen
The amount of data the kstat provides in bytes.
When requesting kstat data, the program specifies the amount of
space available at
.Va ks_data
by setting this variable.
.El
.Sh FILES
.Bl -tag -width Pa -compact
.It Pa /dev/kstat
.El
.Sh SEE ALSO
.\".Xr kstat 1 ,
.Xr kstat_create 9 ,
.Xr kstat_kv_init 9
.Sh HISTORY
The
.Nm
device appeared in
.Ox 6.8 .