dscrctl Command

Purpose

Sets the default prefetch characteristics of an operating system.

Syntax

To query the characteristics of the hardware streams on the computer:

dscrctl -q

To set the default prefetch depth of the operating system on the computer, temporarily (for the current session) or permanently (after each restart operation):

dscrctl [-n] [-b] -s dscr_value

To cancel a permanent setting of the default prefetch depth of the operating system at start time:

dscrctl -c

Description

The dscrctl -q subcommand displays the number of hardware streams, and default prefetch depth of the platform and the operating system. Any user can run this subcommand.

The dscrctl -s subcommand sets the default prefetch depth of the operating system. You must have root authority to run this subcommand. This default value can be changed either for the current session by using -n flag, at start time by using -b flag, or for both current session and at start time by using -n -b flags together with the dscrctl command.

The dscrctl -c option cancels the default prefetch depth setting of the operating system at start time. This option removes the dscrctl command from the /etc/inittab file, and therefore takes effect after the next restart operation.

Flags

-q: Displays the number of hardware streams that are supported by the platform and also displays the values of the default prefetch depth of the firmware and the operating system.
-c: Cancels a permanent setting of the default prefetch depth at start time by removing the dscrctl command from the /etc/inittab file.
-n: Changes the run time value of the default prefetch depth of the operating system. This flag is used in conjunction with the -s flag. The change is not persistent from one boot operation to the next.
-b: Makes the change persistent across boot operations by adding the dscrctl command to the /etc/inittab file. This flag is used in conjunction with the -s flag.
-s dscr_value: Defines the value for the new default prefetch depth of the operating system. The value is treated as a decimal number, unless it starts with 0x in which case it is treated as a hexadecimal number.

Examples

To set the value of the default prefetch depth of the operating system to 13 for the current session, enter:
```
# dscrctl -n -s 13
```

To show the current settings of the hardware stream mechanism, enter:

# dscrctl -q

The following output is displayed:

Current DSCR settings:
Data Streams Version = V2.06
number_of_streams = 16
platform_default_pd = 0x5 (DPFD_DEEP)
os_default_pd = 0xd (DSCR_SSE | DPFD_DEEP)