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<html>
<head>
<title>Moss | Scheduling Simulator | User Guide</title>
</head>
<body bgcolor="#ffffff">
<h1>
MOSS Scheduling Simulator
<br>User Guide</h1>
<h2>Purpose</h2>
<p>
This document is a user guide for the MOSS
Scheduling Simulator. It explains how to use the simulator
and describes the various input and output files used
by the simulator.
The MOSS software
is designed for use with
<a href="http://www.cs.vu.nl/~ast/">Andrew S. Tanenbaum</a>,
<a href="http://vig.prenhall.com/catalog/academic/product/1,4096,0130313580,00.html">Modern Operating Systems, 2nd Edition</a>
(<a href="http://www.prenhall.com/">Prentice Hall</a>, 2001).
The Scheduling Simulator was written by
<a href="http://www.cs.earlham.edu/~odo/">Alex Reeder</a>
(<a href="mailto:alexr@e-sa.org"><i>alexr@e-sa.org</i></a>).
This user guide was written by
<a href="http://www.ontko.com/~rayo/">Ray Ontko</a>
(<a href="mailto:rayo@ontko.com"><i>rayo@ontko.com</i></a>).
<p>
This user guide assumes that you have already installed and tested
the simulator. If you are looking for installation information,
please read the
<a href="install_unix.html">Installation Guide for
Unix/Linux/Solaris/HP-UX Systems</a> or the
<a href="install_windows.html">Installation Guide for
Win95/98/Me/NT/2000 Systems</a>.
</p>
<h2>Introduction</h2>
<p>
The scheduling simulator illustrates the behavior of scheduling
algorithms against a simulated mix of process loads. The user can
specify the number of processes, the mean and standard deviation
for compute time and I/O blocking time for each process, and the
duration of the simulation. At the end of the simulation a
statistical summary is presented. Students may also be asked to
write their own scheduling algorithms to be used with process
loads defined by the instructor.
<h2>Running the Simulator</h2>
<p>
The program reads
a configuration file (<tt>scheduling.conf</tt>)
and writes two output files (<tt>Summary-Results</tt>
and <tt>Summary-Processes</tt>).
<p>
To run the program, enter the following command line.
<blockquote><pre>
$ java Scheduling scheduling.conf
</pre></blockquote>
<p>
The program will display "Working..." while the simulation
is working, and "Completed." when the simulation is complete.
</p>
<blockquote><pre>
Working...
Completed.
</pre></blockquote>
<p>
The simulator reads parameters from the configuration file
("scheduling.conf").
It creates a
specified number of processes, each of which blocks for
input or output after a number of milliseconds that can be specified
for each process. Each process is allowed to run for a
randomly generated amount of time, with the amount of time
constrained by a specified average (mean) in milliseconds,
and standard deviations from that average. The simulation
may also be bounded in the total length of its run.
<p>
After reading the configuration file, the
scheduling algorithm then "runs" the processes, causing
each to block for input or output after the specified interval
until all processes have completed their randomly generated
amount of runtime, or until the maximum amount of runtime for
the simulation is exceeded.
<p>
As the simulation proceeds, a log file ("Summary-Processes")
is generated which shows the activity of the scheduling algorithm
as it considers each process in the process queue.
<p>
After the simulation halts, a summary report ("Summary-Results")
is generated which shows statistics for each process and for the
simulation as a whole.
</p>
<h2>The Configuration File</h2>
<p>
The configuration file (<tt>scheduling.conf</tt>)
is used to specify various parameters for the
simulation, including:
</p>
<ul>
<li>the number of processes,
<li>the mean runtime for a process,
<li>the standard deviation in runtime for a process,
<li>for each process, how long the process runs before it blocks for input or
output, and
<li>how long the simulation should run.
</ul>
<h3>Configuration File Options</h3>
<p>There are a number of options which can
be specified in the configuration file. These are
summarized in the table below.
</p>
<table border="1" cellspacing="0">
<tr>
<th>Keyword</th>
<th>Values</th>
<th>Description</th>
</tr>
<tr>
<td valign="top"><tt>numprocess</tt></td>
<td valign="top"><i>n</i></td>
<td valign="top">The number of processes to create for
the simulation.</td>
</tr>
<tr>
<td valign="top"><tt>meandev</tt></td>
<td valign="top"><i>n</i></td>
<td valign="top">The average length of time in milliseconds
that a process should execute before terminating.</td>
</tr>
<tr>
<td valign="top"><tt>standdev</tt></td>
<td valign="top"><i>n</i></td>
<td valign="top">The number of standard deviations from the
average length of time a process should execute before terminating.<td>
</tr>
<tr>
<td valign="top"><tt>process</tt></td>
<td valign="top"><i>n</i></td>
<td valign="top">The amount of time in milliseconds that
the process should execute before blocking for input or output.
There should be a separate <tt>process</tt> directive for
each process specified by the <tt>numprocess</tt> directive.</td>
</tr>
<tr>
<td valign="top"><tt>runtime</tt></td>
<td valign="top"><i>n</i></td>
<td valign="top">The maximum amount of time the simulation should run
in milliseconds.</td>
</tr>
</table>
<h3>Sample Configuration File</h3>
<p>
The "scheduling.conf" configuration file looks like this:
<blockquote><pre>
// # of Process
numprocess 3
// mean deivation
meandev 1100
// standard deviation
standdev 510
// process # I/O blocking
process 100
process 500
process 30
// duration of the simulation in milliseconds
runtime 5000
</pre></blockquote>
<h2>The Summary-Results File</h2>
<p>
The Summary-Results file contains a summary report describing
the simulation and includes one line of summary information
for each process. The fields and columns in the report
are described in the following table.
</p>
<table border="1">
<tr>
<th>Field</th>
<th>Description</th>
</tr>
<tr>
<td valign="top">Scheduling Type:</td>
<td valign="top">The type of the scheduling algorithm used.
The value displayed is "hard coded" in the SchedulingAlgorithm.java
file.</td>
</tr>
<tr>
<td valign="top">Scheduling Name:</td>
<td valign="top">The name of the scheduling algorithm used.
The value displayed is "hard coded" in the SchedulingAlgorithm.java
file.</td>
</tr>
<tr>
<td valign="top">Simulation Run Time:</td>
<td valign="top">The number of milliseconds that the simulation
ran. This may be less than or equal to the total amount of
time specified by the "runtime" configuration parameter.</td>
</tr>
<tr>
<td valign="top">Mean:</td>
<td valign="top">The average amount of runtime for the processes
as specified by the "meandev" configuration parameter.</td>
</tr>
<tr>
<td valign="top">Standard Deviation:</td>
<td valign="top">The standard deviation from the average
amount of runtime for the processes as specified by the
"standdev" configuration parameter.</td>
</tr>
<tr>
<td valign="top">Process #</td>
<td valign="top">The process number assigned to the process
by the simulator. The process number is between 0 and n-1,
where n is the number specified by the "numprocess" configuration
parameter.</td>
</tr>
<tr>
<td valign="top">CPU Time</td>
<td valign="top">The randomly generated total runtime for the
process in milliseconds. This is determined by the
"meandev" and "standdev" parameters in the configuration
file.</td>
</tr>
<tr>
<td valign="top">IO Blocking</td>
<td valign="top">The amount of time the process runs before it
blocks for input or output. This is specified for each process
by a "process" directive in the configuration file.</td>
</tr>
<tr>
<td valign="top">CPU Completed</td>
<td valign="top">The amount of runtime in milliseconds completed for
the process. Note that this may be less than the CPU Time
for the process if the simulator runs out of time as specified
by the "runtime" configuration parameter.</td>
</tr>
<tr>
<td valign="top">CPU Blocked</td>
<td valign="top">The number of times the process blocked for
input or output during the simulation.</td>
</tr>
</table>
<h3>Sample Summary-Results File</h3>
<p>
The output "Summary-Results" file looks something like this:
</p>
<blockquote><pre>
Scheduling Type: Batch (Nonpreemptive)
Scheduling Name: First-Come First-Served
Simulation Run Time: 2750
Mean: 1100
Standard Deviation: 510
Process # CPU Time IO Blocking CPU Completed CPU Blocked
0 1372 (ms) 100 (ms) 1372 (ms) 13 times
1 689 (ms) 500 (ms) 689 (ms) 1 times
2 689 (ms) 30 (ms) 689 (ms) 22 times
</pre></blockquote>
<h2>The Summary-Processes File</h2>
<p>
The Summary-Processes file contains a log of the actions
taken by the scheduling algorithm as it considers each
process in the scheduling queue.
</p>
<p>
Each line in the log file is of the following form:
<blockquote><pre>
Process: <i>process-number</i> <i>process-status</i>... (<i>cpu-time</i> <i>block-time</i> <i>accumulated-time</i> <i>accumulated-time</i>)
</pre></blockquote>
<p>
The fields in the line are described in the table below.
</p>
<table border="1">
<tr>
<th>Field</th>
<th>Description</th>
</tr>
<tr>
<td valign="top"><i>process-number</i></td>
<td valign="top">The process number assigned to the process by the simulator.
This is a number between 0 and n-1, where n is the
value specified for the "numprocess" configuration parameter.</td>
</tr>
<tr>
<td valign="top"><i>process-status</i></td>
<td valign="top">The status of the process at this point
in time. If "registered" then the process is under consideration
by the scheduling algorithm. If "I/O blocked", then the
scheduling algorithm has noticed that the process is blocked
for input or output.
If "completed", then the scheduling algorithm has noticed
that the process has met or exceeded its allocated execution
time.</td>
</tr>
<tr>
<td valign="top"><i>cpu-time</i></td>
<td valign="top">The total amount of run time allowed for this
process. This number is randomly generated for the process
based on the
"meandev" and "standdev" values specified in the configuration
file.</td>
</tr>
<tr>
<td valign="top"><i>block-time</i></td>
<td valign="top">The amount of time in milliseconds to execute
before blocking process. This number is specified for the process
by the "process" directive in the configuration file.</td>
</tr>
<tr>
<td valign="top"><i>accumulated-time</i></td>
<td valign="top">The total amount of time process has executed in
milliseconds. (This number appears twice in the log file; one
should be removed).
</tr>
</table>
<h3>Sample Summary-Processes File</h3>
<p>
The output "Summary-Processes" file looks something like this:
</p>
<blockquote><pre>
Process: 0 registered... (1372 100 0 0)
Process: 0 I/O blocked... (1372 100 100 100)
Process: 1 registered... (689 500 0 0)
Process: 1 I/O blocked... (689 500 500 500)
Process: 0 registered... (1372 100 100 100)
Process: 0 I/O blocked... (1372 100 200 200)
Process: 1 registered... (689 500 500 500)
Process: 1 completed... (689 500 689 689)
Process: 0 registered... (1372 100 200 200)
Process: 0 I/O blocked... (1372 100 300 300)
Process: 2 registered... (689 30 0 0)
Process: 2 I/O blocked... (689 30 30 30)
Process: 0 registered... (1372 100 300 300)
Process: 0 I/O blocked... (1372 100 400 400)
Process: 2 registered... (689 30 30 30)
Process: 2 I/O blocked... (689 30 60 60)
Process: 0 registered... (1372 100 400 400)
Process: 0 I/O blocked... (1372 100 500 500)
Process: 2 registered... (689 30 60 60)
Process: 2 I/O blocked... (689 30 90 90)
Process: 0 registered... (1372 100 500 500)
Process: 0 I/O blocked... (1372 100 600 600)
Process: 2 registered... (689 30 90 90)
Process: 2 I/O blocked... (689 30 120 120)
Process: 0 registered... (1372 100 600 600)
Process: 0 I/O blocked... (1372 100 700 700)
Process: 2 registered... (689 30 120 120)
Process: 2 I/O blocked... (689 30 150 150)
Process: 0 registered... (1372 100 700 700)
Process: 0 I/O blocked... (1372 100 800 800)
Process: 2 registered... (689 30 150 150)
Process: 2 I/O blocked... (689 30 180 180)
Process: 0 registered... (1372 100 800 800)
Process: 0 I/O blocked... (1372 100 900 900)
Process: 2 registered... (689 30 180 180)
Process: 2 I/O blocked... (689 30 210 210)
Process: 0 registered... (1372 100 900 900)
Process: 0 I/O blocked... (1372 100 1000 1000)
Process: 2 registered... (689 30 210 210)
Process: 2 I/O blocked... (689 30 240 240)
Process: 0 registered... (1372 100 1000 1000)
Process: 0 I/O blocked... (1372 100 1100 1100)
Process: 2 registered... (689 30 240 240)
Process: 2 I/O blocked... (689 30 270 270)
Process: 0 registered... (1372 100 1100 1100)
Process: 0 I/O blocked... (1372 100 1200 1200)
Process: 2 registered... (689 30 270 270)
Process: 2 I/O blocked... (689 30 300 300)
Process: 0 registered... (1372 100 1200 1200)
Process: 0 I/O blocked... (1372 100 1300 1300)
Process: 2 registered... (689 30 300 300)
Process: 2 I/O blocked... (689 30 330 330)
Process: 0 registered... (1372 100 1300 1300)
Process: 0 completed... (1372 100 1372 1372)
Process: 2 registered... (689 30 330 330)
Process: 2 I/O blocked... (689 30 360 360)
Process: 2 registered... (689 30 360 360)
Process: 2 I/O blocked... (689 30 390 390)
Process: 2 registered... (689 30 390 390)
Process: 2 I/O blocked... (689 30 420 420)
Process: 2 registered... (689 30 420 420)
Process: 2 I/O blocked... (689 30 450 450)
Process: 2 registered... (689 30 450 450)
Process: 2 I/O blocked... (689 30 480 480)
Process: 2 registered... (689 30 480 480)
Process: 2 I/O blocked... (689 30 510 510)
Process: 2 registered... (689 30 510 510)
Process: 2 I/O blocked... (689 30 540 540)
Process: 2 registered... (689 30 540 540)
Process: 2 I/O blocked... (689 30 570 570)
Process: 2 registered... (689 30 570 570)
Process: 2 I/O blocked... (689 30 600 600)
Process: 2 registered... (689 30 600 600)
Process: 2 I/O blocked... (689 30 630 630)
Process: 2 registered... (689 30 630 630)
Process: 2 I/O blocked... (689 30 660 660)
Process: 2 registered... (689 30 660 660)
Process: 2 completed... (689 30 689 689)
</pre></blockquote>
<h2>Suggested Exercises</h2>
<ol>
<li>Create a configuration file in which all processes run
an average of 2000 milliseconds with a standard deviation of
zero, and which are blocked for input or output every 500 milliseconds.
Run the simulation for 10000 milliseconds with 2 processes.
Examine the two output files. Try again for 5 processes. Try again for
10 processes. Explain what's happening.
<p><!-- --></p>
<li>Implement a round-robin scheduling algorithm. (Hint:
see the Run() method in SchedulingAlgorithm.java).
<p><!-- --></p>
</ol>
<h2>To Do</h2>
<ol>
<li>Consider changing the configuration parameter "meandev"
to "run_time_average". The word "dev"
doesn't belong here. It would be nice if this were
the average amount of time a process runs before
blocking for input or output instead of the total runtime.
<p><!-- --></p>
<li>Consider changing the configuration parameter "standdev"
to "run_time_stddev".
It would be nice if this were the
number of standard deviations from the average time a
process runs before blocking for input or output instead
of the total runtime.
<p><!-- --></p>
<li>Consider renaming the "Run()" method in SchedulingAlgorithm
to "run()". By convention in java, method names begin with
a lowercase letter. Also, add some internal documentation
to SchedulingAlgorithm to facilitate understanding by students
and instructors, and add external documentation regarding
the implementation of new scheduling algorithms to this user guide.
<p><!-- --></p>
<li>Consider adding a configuration parameter for "block_time_average"
which would be the average amount of time in milliseconds that a process
remains blocked for input or output before resuming execution.
This would help eliminate the need for the "process" directive.
<p><!-- --></p>
<li>Consider adding a configuration parameter for "block_time_stddev"
which would be the number of standard deviations from the average
time a process remains blocked for input out output before
resuming execution. This would help eliminate the need for the
"process" directive.
<p><!-- --></p>
<li>Consider adding a configuration parameter for "quantum" which
specifies the number of milliseconds that a process is allowed to
execute before being re-considered by the scheduling algorithm.
<p><!-- --></p>
<li>Consider modifying the format of the Summary-Processes log file.
The total cpu time for the process is repeated in the last column
and should be eliminated. It would be nice if the total elapsed
milliseconds (system clock) were present at the beginning of the line
so that we can see when things happened exactly during the simulation.
If we switch to the meanings of the various parameters as suggested
above, we may want to rethink the overall format of the lines as
well.
<p><!-- --></p>
<li>Consider adding a configuration parameter for "summary_file" so that
the name for the Summary-Results file can be specified
in the configuration file.
<p><!-- --></p>
<li>Consider adding a configuration parameter for "log_file" so
that the name for the Summary-Processes file can be
specified in the configuration file.
<p><!-- --></p>
<li>Consider adding a graphical user
interface that allowed the user to view the simulation
as it proceeded. This might show a summary of the
number of blocked processes and executable processes,
the percentage of idle time, and even the current status
of each process. This might be enabled by a configuration
parameter "show_graphics true". A "step" button might
allow the simulation to proceed 1000 milliseconds at a
time, or a "run" button might allow it to update every
1000 milliseconds until the simulation completes. A
"reset" button might restart the simulation to its original
values, and there might be menu options to allow the user
to override the parameter values given in the configuration file.
<p><!-- --></p>
</ol>
<h2>Copyright</h2>
&copy; Copyright 2001, Prentice-Hall, Inc.
<p>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
<p>
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
<p>
You should have received a copy of the GNU General Public License
along with this program (see <a href="COPYING.TXT">COPYING.TXT</a>);
if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
<p>
Please send suggestions, corrections, and comments to
<a href="http://www.ontko.com/~rayo/">Ray Ontko</a>
(<a href="mailto:rayo@ontko.com"><i>rayo@ontko.com</i></a>).
<p>
<i>Last updated: May 23, 2001</i>
</body>
</html>
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