freebsd-dev/lib/libgeom/libgeom.3

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.Dd February 8, 2003
.Dt LIBGEOM 3
.Os
.Sh NAME
.Nm geom_stats_open ,
.Nm geom_stats_close ,
.Nm geom_stats_resync ,
.Nm geom_stats_snapshot_get ,
.Nm geom_stats_snapshot_free ,
.Nm geom_stats_snapshot_timestamp ,
.Nm geom_stats_snapshot_reset ,
.Nm geom_stats_snapshot_next
.Nd userland API library for kernel GEOM subsystem
.Sh LIBRARY
.Lb libgeom
.Sh SYNOPSIS
.In libgeom.h
.Ss "Statistics Functions"
.Ft void
.Fn geom_stats_close void
.Ft int
.Fn geom_stats_open void
.Ft void
.Fn geom_stats_resync void
.Ft "void *"
.Fn geom_stats_snapshot_get void
.Ft void
.Fn geom_stats_snapshot_free "void *arg"
.Ft void
.Fn geom_stats_snapshot_timestamp "void *arg" "struct timespec *tp"
.Ft void
.Fn geom_stats_snapshot_reset "void *arg"
.Ft "struct g_stat *"
.Fn geom_stats_snapshot_next "void *arg"
.Sh DESCRIPTION
The
.Nm geom
library contains the official and publicized API for
interacting with the GEOM subsystem in the kernel.
.Ss "Statistics Functions"
GEOM collects statistics data for all consumers and providers, but does
not perform any normalization or presentation on the raw data, this is
left as an excercize for user-land presentation utilities.
.Pp
The
.Fn geom_stats_open
and
.Fn geom_stats_close
functions open and close the necessary pathways to access the raw
statistics information in the kernel.
These functions are likely to
open one or more files and cache the file descriptors locally.
.Fn geom_stats_open
returns zero on success, and sets
.Va errno
if not.
.Pp
The
.Fn geom_stats_resync
function will check if more statistics collection points have been
added in the kernel since
.Fn geom_stats_open
or the previous call to
.Fn geom_stats_resync .
.Pp
The
.Fn geom_stats_snapshot_get
function
will acquire a snapshot of the raw data from the kernel, and while a
reasonable effort is made to make this snapshot as atomic and consistent
as possible, no guarantee is given that it will actually be so.
The snapshot must be freed again using the
.Fn geom_stats_snapshot_free
function.
.Fn geom_stats_snapshot_get
returns
.Dv NULL
on failure.
.Pp
The
.Fn geom_stats_snapshot_timestamp
function
provides access to the timestamp acquired in the snapshot.
.Pp
The
.Fn geom_stats_snapshot_reset
and
.Fn geom_stats_snapshot_next
functions
provide an iterator over the statistics slots in the snapshot.
The
.Fn geom_stats_snapshot_reset
function
forces the internal pointer in the snapshot back to before the first item.
The
.Fn geom_stats_snapshot_next
function
returns the next item, and
.Dv NULL
if there are no more items in the snapshot.
.Sh AUTHORS
.An Poul-Henning Kamp Aq phk@FreeBSD.org
.Sh HISTORY
The
.Nm geom
library appeared in
.Fx 5.1 .