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GSCHED(8)               FreeBSD System Manager's Manual              GSCHED(8)

NAME
     gsched - control utility for disk scheduler GEOM class

SYNOPSIS
     gsched create [-v] [-a algorithm] provider ...
     gsched insert [-v] [-a algorithm] provider ...
     gsched configure [-v] [-a algorithm] node ...
     gsched destroy [-fv] node ...
     gsched reset [-v] node ...
     gsched { list | status | load | unload }

DESCRIPTION
     The gsched utility (also callable as geom sched ...) changes the
     scheduling policy of the requests going to a provider.

     The first argument to gsched indicates an action to be performed:

     create         Create a new provider and geom node using the specified
                    scheduling algorithm.  algorithm is the name of the
                    scheduling algorithm used for the provider.  Available
                    algorithms include: rr, which implements anticipatory
                    scheduling with round robin service among clients; as,
                    which implements a simple form of anticipatory scheduling
                    with no per-client queue.

                    If the operation succeeds, the new provider should appear
                    with name /dev/<dev>.sched..  The kernel module
                    geom_sched.ko will be loaded if it is not loaded already.

     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.

                    A subsequent 'destroy' will remove the newly created geom
                    and hook the provider back to the original geom.
                    algorithm

     configure      Configure existing scheduling provider.  It supports the
                    same options as the create command.

     destroy        Destroy the geom specified in the parameter.

     reset          Do nothing.

     list | status | load | unload
                    See geom(8).

     Additional options:

     -f     Force the removal of the specified provider.

     -v     Be more verbose.

SYSCTL VARIABLES
     The following sysctl(8) variables can be used to control the behavior of
     the SCHED GEOM class.  The default value is shown next to each variable.

     kern.geom.sched.debug: 0
             Debug level of the 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.

EXIT STATUS
     Exit status is 0 on success, and 1 if the command fails.

EXAMPLES
     The following example shows how to create a scheduling provider for disk
     /dev/da0 , and how to destroy it.

           # 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.

SEE ALSO
     geom(4), geom(8)

HISTORY
     The gsched utility appeared in April 2010.

AUTHORS
     Fabio Checconi <fabio@FreeBSD.org>
     Luigi Rizzo <luigi@FreeBSD.org>

FreeBSD 11.0-PRERELEASE         April 12, 2010         FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | SYSCTL VARIABLES | EXIT STATUS | EXAMPLES | SEE ALSO | HISTORY | AUTHORS

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