GSCHED(8)		  BSD 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 schedul‐
     ing 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 sched‐
		uling 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 sim‐
		ple 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.

     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 informa‐
	     tion 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/ada0, and how to destroy it.

	   # Load the geom_sched module:
	   kldload geom_sched
	   # Load some scheduler classes used by geom_sched:
	   kldload gsched_rr
	   # Configure device ada0 to use scheduler "rr":
	   geom sched insert -a rr ada0
	   # Now provider ada0 uses the "rr" algorithm;
	   # the new geom is ada0.sched.
	   # Remove the scheduler on the device:
	   geom sched destroy -v ada0.sched.

SEE ALSO
     geom(4), geom(8)

HISTORY
     The gsched utility first appeared in FreeBSD 8.1.

AUTHORS
     Fabio Checconi ⟨fabio@FreeBSD.org⟩
     Luigi Rizzo ⟨luigi@FreeBSD.org⟩

BSD				 July 26, 2012				   BSD