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.Dd August 16, 2010
.Dt DSCHED 4
.Os
.Sh NAME
.Nm dsched
.Nd kernel disk scheduler framework
.Sh DESCRIPTION
The
.Nm
framework implements a disk scheduler framework that can be
used to switch disk scheduling policies at runtime for each
disk in the system.
The
.Nm
framework and the policies for each disk can be managed via
.Xr loader 8
tunables and via
.Xr sysctl 8
variables.
.Sh LOADER TUNABLES
Tunables can be set at the
.Xr loader 8
prompt before booting the kernel or stored in
.Xr loader.conf 5 .
.Bl -tag -width ".Va dsched.policy.default"
.It Va dsched.policy.default
This tunable sets the default policy used for every device that
has no policy specified via any of the other tunables.
.It Va dsched.policy.da0
This tunable sets the dsched policy for the disk da0.
The default value is 0.
.It Va dsched.policy.da
This tunable sets the dsched policy for all disks created by
the driver
.Xr da 4 .
.El
.Sh SYSCTL VARIABLES
.Bl -tag -width ".Va dsched.policy.SN39A39"
.It Va dsched.debug
set the debug-level, 0 means no debugging, 5 for maximum.
.It Va dsched.policy.default
shows and sets the current default dsched policy.
.It Va dsched.policy.da0
shows and sets the current policy for the disk da0.
.It Va dsched.policy.SN39A39
shows and sets the current policy for the disk with serial number
SN39A39.
.El
.Pp
The following are informative only:
.Bl -tag -width ".Va dsched.policy.SN39A39"
.It Va dsched.policies
shows all available dsched policies, separated by spaces.
.El
.Sh SEE ALSO
.Xr loader.conf 5 ,
.Xr sysctl.conf 5 ,
.Xr dsched 9
.Sh HISTORY
The
.Nm
framework first appeared in
.Dx 2.5 .
.Sh AUTHORS
The
.Nm
framework was written by
.An Alex Hornung .