Frequently Asked Questions and Troubleshooting Tips

This section provides recommendations to obtain the maximum performance from Accelerator Plus.

Use the Latest Release

The performance of the Accelerator Plus scheduler is frequently updated. Using the most current version is recommended.

Use the vwn Wrapper

The wrapper vwn (alias for vw -N) avoids communication with vovserver. An example is shown below:
% wx run -wrapper vwn sleep 0

The benefit is of using vwn is speed.

The disadvantage is that jobs that require the -wl option cannot be run. However, this disadvantage may be not be significant, as -wl adds a relatively high load for what it does: -wl requires an extra notify client to handle the event generated when the job terminates.

Disable Wait Reasons

If analyzing what causes wait time in the workload, the wait reason analysis can be disabled as shown below:
# In policy.tcl
set config(enableWaitReasons) 0
Wait time analysis can then be re-enable as needed as shown below:
% wx cmd vovsh -x 'vtk_server_config enableWaitReasons 1'

### collect some data for a few minutes, then

% wx cmd vovsh -x 'vtk_server_config enableWaitReasons 0'

Disable File Access

Disabling file access is mostly a high-reliability option. By disabling file access, the vovserver never looks at any of the files in the user workspaces, which avoids the risk of disk slowness or disk unavailability. An example is shown below:
% wx cmd vovsh -x 'vtk_server_config disablefileaccess 2'

Reduce Update Rate of Notify Clients

Notify clients, clients that are tapping the event stream from vovserver (such as wx gui, voveventmon or wx run -wl), are updated immediately in the inner loop of the scheduler. If the environment includes hundreds of such clients, it may be beneficial to slow down the update rate by setting the parameter notifySkip. The default value is 0: no skip. Typically, the more events that take place, the more events that can be skipped without notice. For example, if several events are taking place, setting notifySkip to 100, fewer updates may not be noticed. If the number of events is small, a one-second delay may be noticed in some updates of the GUI. skipped without notice.
Note: Regardless of the setting, the maximum time between updates is one second.
# In policy.tcl
set config(notifySkip) 100