Enable automatic CPU frequency selection

To enable automatic CPU Frequency selection, there are three requirements, after completing the configuration:

  1. A global (cluster-level) performance threshold configuration file (lsb.threshold) is required, to control the minimize energy or running time policy.
  3. Coefficient data must be generated and saved in database.

The threshold file (lsb.threshold) is available at the location specified by the parameter PERFORMANCE_THRESHOLD_FILE in lsb.params. The default location is $LSF_ENVDIR/lsbatch/cluster_name/configdir/lsb.threshold.

There are two parts in the threshold file:

  • minimize energy policy: The purpose of this policy is to save energy. With this policy, LSF will select a frequency that is equal to or less than the default CPU frequency and the time variation is equal to or less than the threshold value, which can save the most energy. The value should be a positive value (or 0). The default threshold value is 0.
  • minimize time policy: The purpose of this policy is to improve performance. The value must be a negative value. This policy will allow the job to run in a frequency that is higher than the default frequency and is only available when the default frequency is less than the nominal frequency. LSF will only consider the frequency range that is higher than the default frequency. When a job runs with this policy, LSF checks the time variation from the nominal to the default frequency. The frequency is used for the job when the time variation is less than or equal to the corresponding threshold value (the absolute value of time variation is large than or equal to corresponding threshold’s absolute value), otherwise, LSF checks the next frequency. The job will run in the default frequency when there is no frequency that matches the specified threshold value. You must specify at least one frequency value that is larger than the default CPU frequency and less than or equal to the maximum available frequency. The available frequency list is available at (/sys/devices/system/cpu/cpu*/cpufreq/scaling_available_frequencies. If it is not in the available frequency list, the frequency will be ignored. For other frequencies larger than the default CPU frequency, LSF will automatically calculate the value based on the difference of these two values and (default frequency and defined frequency). LSF will calculate the increase between each frequency and use that to get all frequencies that are larger than the default CPU frequency.

The lsb.threshold file may appear as follows:

# Copyright International Business Machines Corp,1993-2006, 2013
# Minimize energy policy
Begin Min_Energy
End  Min_Energy
# Minimize run time policy
Begin Min_Time
2100000KHz     -2      
2200000KHz     -4
2300000KHz     -9
2400000KHz     -12
2500000KHz     -15
2700000KHz     -20
End Min_Time

The following rules must be followed when defining the lsb.threshold file:

  • Example definitions are commented with a pound sign (#) in the sample lsb.threshold file. Remove the # to enter your own values for the example definitions. If no lines are uncommented, default values will be used for all definitions.