Running the Hot Restart Demonstration Program

The Sun Embedded Workshop software includes a graphical demonstration of the hot restart feature. The demonstration is based on a well-known program, Xmaze, which has been slightly modified to make it hot restartable. Some of the program's data is stored in persistent memory, which means that when the program is restarted, it starts at a point close to the point it had reached prior to the restart. The resulting application is a ChorusOS process called xdemo.

To run the hot restart demonstration program, do the following:

1. Ensure that your system features are correctly set for hot restart (see "Features".

2. Adjust the following system parameters to suit the memory requirements of the Xmaze demonstration program using Ews or the configurator(1CC) command line utility, as shown in the following table:

   Tunable parameter	Description	Required Value
   pmm.rambankSize	Size of persistent memory bank (in bytes)	0x400000
   kern.exec.dflSysStackSize	Default system stack size (in bytes)	0x8000

3. Configure your system image build to include the X11 library and ChorusOS examples directory (if this is not already the case):

   % make reconfigure NEWCONF '_s <src_dir>/opt/X11'

4. If you have made changes to the system image since the previous build, rebuild the system and copy the system image to the appropriate location (for example, the boot directory if you are using tftp-based boot). Reboot the target machine.

5. Ensure that a copy of the xdemo process is present in a directory mounted on the target machine. If you use the make root command, a copy of the process is already stored in build_dir/root/bin/examples. If this directory is not mounted, or to use a different mounted directory, do the following:

   $ cp build_dir/BUILD_EXAMPLES/restartDemo/xdemo example_directory

6. Set the target machine's DISPLAY environment variable to the host machine:

   $ rsh target setenv DISPLAY host_IP_address:0.0

7. Run the restartable process:

   $ rsh target arun -g 0 example_directory/xdemo

   The process will be run as a member of the restart group with a group ID 0.

The Xmaze demonstration appears on the screen. As the demonstration runs, it periodically stores its state as data in persistent memory. Allow the demonstration to run for a short time, then restart the process by typing the following command on the host console:

$ rsh target akill pid

The process identifier (PID) is printed on the host console when the process starts.

The process is restarted, and the Xmaze demonstration continues from a point close to where it left off before the restart.

The akill command provoked the restart because it was not called with the restart-specific option -g. To kill the Xmaze demonstration process without restarting it, type:

$ rsh target akill -g 0

Because the xdemo process runs from the command line it is a direct process, and will be started automatically by the system when the site is restarted. To confirm this, rerun the process, and provoke a site restart by typing the following:

$ rsh target restart

After the system has been re-initialized, the demonstration will be restarted.

This is a basic illustration of the use of the hot restart feature. The site restart is provoked manually from the command line. As an alternative, try restarting the process using akill -g sufficiently frequently to trigger an automatic site restart. To do this, set the system's restart policy to be more sensitive to process failure. The following example configuration will invoke a site restart if the process is restarted twice within four seconds: