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+.\" Copyright (c) 2009-2010 Fabio Checconi
+.\" Copyright (c) 2009-2010 Luigi Rizzo, Universita` di Pisa
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd April 12, 2010
+.Dt GSCHED 8
+.Os
+.Sh NAME
+.Nm gsched
+.Nd "control utility for disk scheduler GEOM class"
+.Sh SYNOPSIS
+.Nm
+.Cm create
+.Op Fl v
+.Op Fl a Ar algorithm
+.Ar provider ...
+.Nm
+.Cm insert
+.Op Fl v
+.Op Fl a Ar algorithm
+.Ar provider ...
+.Nm
+.Cm configure
+.Op Fl v
+.Op Fl a Ar algorithm
+.Ar node ...
+.Nm
+.Cm destroy
+.Op Fl fv
+.Ar node ...
+.Nm
+.Cm reset
+.Op Fl v
+.Ar node ...
+.Nm
+.Cm { list | status | load | unload }
+.Sh DESCRIPTION
+The
+.Nm
+utility (also callable as
+.Nm geom sched ... )
+changes the scheduling policy of the requests going to a provider.
+.Pp
+The first argument to
+.Nm
+indicates an action to be performed:
+.Bl -tag -width ".Cm configure"
+.It Cm create
+Create a new provider and geom node using the specified scheduling algorithm.
+.Ar algorithm
+is the name of the scheduling algorithm used for the provider.
+Available algorithms include:
+.Ar rr ,
+which implements anticipatory scheduling with round robin service
+among clients;
+.Ar as ,
+which implements a simple form of anticipatory scheduling with
+no per-client queue.
+.Pp
+If the operation succeeds, the new provider should appear with name
+.Pa /dev/ Ns Ao Ar dev Ac Ns Pa .sched. .
+The kernel module
+.Pa geom_sched.ko
+will be loaded if it is not loaded already.
+.It Cm insert
+Operates as "create", but the insertion is "transparent",
+i.e. the existing provider is rerouted to the newly created geom,
+which in turn forwards requests to the existing geom.
+This operation allows one to start/stop a scheduling service
+on an already existing provider.
+.Pp
+A subsequent 'destroy' will remove the newly created geom and
+hook the provider back to the original geom.
+.Ar algorithm
+.It Cm configure
+Configure existing scheduling provider. It supports the same options
+as the
+.Nm create
+command.
+.It Cm destroy
+Destroy the geom specified in the parameter.
+.It Cm reset
+Do nothing.
+.It Cm list | status | load | unload
+See
+.Xr geom 8 .
+.El
+.Pp
+Additional options:
+.Bl -tag -width ".Fl f"
+.It Fl f
+Force the removal of the specified provider.
+.It Fl v
+Be more verbose.
+.El
+.Sh SYSCTL VARIABLES
+The following
+.Xr sysctl 8
+variables can be used to control the behavior of the
+.Nm SCHED
+GEOM class.
+The default value is shown next to each variable.
+.Bl -tag -width indent
+.It Va kern.geom.sched.debug : No 0
+Debug level of the
+.Nm SCHED
+GEOM class.
+This can be set to a number between 0 and 2 inclusive.
+If set to 0 minimal debug information is printed, and if set to 2 the
+maximum amount of debug information is printed.
+.El
+.Sh EXIT STATUS
+Exit status is 0 on success, and 1 if the command fails.
+.Sh EXAMPLES
+The following example shows how to create a scheduling provider for disk
+.Pa /dev/da0
+, and how to destroy it.
+.Bd -literal -offset indent
+# Load the geom_sched module:
+kldload geom_sched
+# Load some scheduler classes used by geom_sched:
+kldload gsched_rr gsched_as
+# Configure device ad0 to use scheduler 'rr':
+geom sched insert -s rr ad0
+# Now provider ad0 uses the 'rr' algorithm;
+# the new geom is ad0.sched.
+# Remove the scheduler on the device:
+geom sched destroy -v ad0.sched.
+.Ed
+.Pp
+.Sh SEE ALSO
+.Xr geom 4 ,
+.Xr geom 8
+.Sh HISTORY
+The
+.Nm
+utility appeared in April 2010.
+.Sh AUTHORS
+.An Fabio Checconi Aq fabio@FreeBSD.org
+.An Luigi Rizzo Aq luigi@FreeBSD.org
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