Computing preferences, version 2

Static and dynamic parameters

"Dynamic" parameters limit BOINC activity and change in response to various factors external to BOINC. Examples include limits on #CPUs, RAM usage, network usage, etc.

Prefs dictionary

The "prefs dictionary" is a name -> value map, containing values that can affect dynamic params. Examples:

• "idle_time": # seconds since last user input
• "time": time of day
• "on_batteries": whether system is running on batteries
• "exclusive_app_running": whether an exclusive app is running
• "non_boinc_cpu_usage": fraction of CPU used for non-BOINC apps recently

These values are updated by the client. In addition, external programs can add items to the dictionary, and update their values, via GUI RPCs. Hence the prefs system is extensible without modifying the client.

Values are doubles; Booleans are encoded as 0/1.

Preference terms

Preferences are expressed in terms of "conditions" that are the conjunction of a set of "terms".

Each term is an assertion about a dictionary item. There are three types of terms:

• "greater than": the value of the item is greater than a number X.
• "nonzero": the value of the item is nonzero (i.e. Boolean true)
• "time range": the value of the item (usually "time") lies in a set of day/week intervals.

A term can also have a "negate" flag, which if set reverses its sense.

The XML representation of a term is

<term>
   <item>item-name</item>
   <type>x</type>                  // 0 = greater than, 1 = nonzero, 2 = time range
   [<negate/>]
   [<thresh>x</thresh>]            // if greater than
   [<time_range>...</time_range>]  // if time range
</term>

and the representation of a time range is

<time_range>
   <start_hour>x</start_hour>
   <end_hour>y</end_hour>
   [
   <day>
      <day_of_week>x</day_of_week>    // 0 .. 6
      <start_hour>x</start_hour>
      <end_hour>y</end_hour>
   <day>
</time_range>

Conditions

A "condition" is the conjunction ("and") of a set of terms, possibly negated. XML format:

<condition>
   [<negate/>]
   <term> ... </term>
   ...
</condition>

If the set if empty, the condition is always true.

Clauses

A "clause" is the combination of a condition and a set of dynamic parameters. XML format:

<clause>
   <condition> ... </condition>
   <dynamic_params> ... </dynamic_params>
<clause>

Preference sets

A "preference set" is a list of clauses. XML format:

<computing_prefs>
   <clause> ... </clause>
   ...
</computing_prefs>

The semantics are as follows. X is a set of dynamic parameters, initially empty. The clauses are processed in order. For each clause C, we evaluate its condition. If the condition is true, we overwrite X with C's dynamic parameters. At the conclusion, X is the dynamic parameters to be enforced by the client.

Example

The following says to use all the CPUs and 90% of the RAM if there has been no user input in 3 minutes, and to use 50% of the CPUs and 50% of the RAM otherwise:

<computing_prefs>
   <clause>
      <condition></condition>
      <dynamic_params>
         <max_ncpus_pct>50</max_ncpus_pct>
         <ram_max_used_frac>.5</ram_max_used_frac>
      </dynamic_params>
   </clause>
   <clause>
      <condition>
         <term>
            <type>gt</type>
            <item>idle_time</time>
            <value>180</value>
         </term>
      </condition>
      <dynamic_params>
         <max_ncpus_pct>100</max_ncpus_pct>
         <ram_max_used_frac>.9</ram_max_used_frac>
      </dynamic_params>
   </clause>
</computing_prefs>