descriptionMuen scheduling plan generator
ownerReto Buerki
last changeThu, 2 Feb 2017 10:29:50 +0000 (11:29 +0100)
readme

Mugenschedcfg

Overview

The mugenschedcfg tool generates scheduling plans for the Muen Separation Kernel (SK) based on a given scheduling configuration. See the tool's usage information (mugenschedcfg -h) for details about how to invoke it. An introduction to the scheduling concept of the Muen SK in general is given in section 3.4.7 of the project report.

The configuration allows the user to specify the following scheduling properties:

Mode of Operation

Each plan specifies multiple levels in CPU tick units. The tick count must increase from one level to the next and also be a multiple of the previous, lower level:

<levels>
 <level ticks="10"/>    <!-- 1 -->
 <level ticks="40"/>    <!-- 2 -->
 <level ticks="160"/>   <!-- 3 -->
 <level ticks="1920"/>  <!-- 4 -->
</levels>

The last level defines the total ticks in this plan (1920 here).

A plan defines which subjects it contains, either by explicit reference:

<subjects>
 <subject ref="s26" minLength="30"/>
 ...
</subjects>

Or by selecting all defined subjects:

<subjects>
 <selectAll>
  <subject ref="s26" minLength="30"/>
 </selectAll>
</subjects>

The above statement selects all defined subjects and adjusts the minLength property of subject s26 for this specific plan. This allows for the flexible definition of subject properties at global and plan-local scope.

Each subject in a given plan specifies at which level it is intended to be scheduled, which basically defines the frequency of the subject in a concrete plan. For example if a subject is scheduled at level 2 in the above example, it would repeat every 40 ticks (if feasible). The tool will plan at least one execution slot of this subject in the given plan depending on the overall configuration and inter-plan dependencies.

Score functions and chains are used to quantify the increase of throughput relative to the assigned scheduling ticks of a single subject or a subject group. It enables the tool to grant more ticks to subjects which benefit the most. Score functions are piecewise linear functions which can be defined at the desired accuracy by specifying x,y coordinates of points on the function graph:

<function name="identity">
 <point x="0.0" y="0.0"/>
 <point x="1.0" y="1.0"/>
</function>

A value y is calculated from a given input value x using linear approximation.

Chains defined at plan scope assign a score function to one or more subjects in the plan.

Performance Properties

Subject performance requirements can be described by the following configuration properties:

Security Properties

Subjects which must not be executed simultaneously can be assigned to exclusive simultaneous domains. The tool enforces that such subjects never run simultaneously on different CPU cores. This mechanism can be used as a potential countermeasure against memory-based side channel attacks.

Subjects which must run on different CPUs can be members of exclusive CPU domains. The tool then schedules the subjects so they are not executed in the same CPU. This mechanism can be used as a potential countermeasure against cache-based side channel attacks (after carefully analyzing the CPU topology of the target platform).

Build & Usage

The tool is part of the Muen project and relies on Muen libraries to compile. It is therefore built as an integral part of the Muen toolchain as described in the main Muen README file.

Visualization

The mugenschedcfg tool provides a Gnuplot script to visualize generated scheduling plan data. This is not only useful to get a quick overview of the generated plans, but it also enables the intuitive verification of specified performance and security properties.

Examples

The PDF depicts a visualization of the complex example scheduling plan specified in the plans/complex.xml file. The configuration declares 12 plans to be generated, with a total of 47 subjects and 4 CPU cores. Each CPU is represented by a different colors in the graph.

The first 3 plans are intended for use during system startup where only a few subjects are active to perform initialization. Plans 4-12 use chains and score functions to prioritize certain subjects depending on the workload.

The following security properties are active in this configuration:

Status and Limitations

The tool has started as a student project during an internship and has since been stabilized by the Muen team. It is still in beta status, so please report bugs you might encounter to the muen-dev mailing list (see below).

The Muen demo system successfully uses the tool to generate scheduling plans automatically during integration. Checkout the policy/Makefile targets in the Muen source tree for details on how this is achieved.

The tool assumes certain properties of the input data which cannot be ensured by XSD 1.1 schema validation. The respective validators to enforce these properties are not yet implemented (see the TODO file).

Contact

If you have any questions regarding the tool or suggestions on how to improve it, please write an email to the Muen development team's mailing list at

muen-dev@googlegroups.com
shortlog
2017-02-02 Reto BuerkiSet exit non-zero on heuristic failure master
2017-02-02 Reto BuerkiMinor correction in README
2017-01-24 Christiane... Initial import of the Mugenschedcfg tool
heads
6 months ago devel
6 months ago master