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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-0AFF5666-6BF9-5022-ADBC-5EFFA743B288" xml:lang="en"><title>ROM |
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13 Paging Guide</title><shortdesc>Describes demand paging when applied to ROM demand paging. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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14 <section id="GUID-D67AB531-76C8-50AE-BBA2-48FC7F47DCDD"><title>Introduction</title> <p>Demand |
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15 paging using ROM demand paging is used when the files to be paged are in the |
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16 core ROM image and not using another file system such as ROFS. </p> </section> |
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17 <section id="GUID-338FBBC7-2B90-4483-B055-2AEA23DAB479"><title>Background information</title><p> The following are useful |
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18 background information for Demand Paging using ROM demand paging:</p><ul> |
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19 <li><p>Demand Paging</p></li> |
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20 <li><p>ROM paging</p></li> |
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21 </ul> </section> |
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22 <section id="GUID-143C5BFF-AC9A-4A83-B20A-79E0A8E9B36E"><title>ROM Demand Paging features</title><p>Demand paging (using |
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23 ROM demand paging) provides the following features compared to <xref href="GUID-CE9EA167-0594-5E61-9640-6B2B63A92EA7.dita">code |
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24 paging</xref> and <xref href="GUID-2B7D04D9-98DE-5284-836D-01DB4FA8949D.dita">writable |
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25 data paging</xref> : </p><ul> |
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26 <li><p>Lower RAM overhead</p></li> |
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27 <li><p>Lower performance overhead.</p></li> |
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28 </ul> </section> |
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29 <section id="GUID-5391A3D1-A6CE-4C1A-8D42-B74A7E77E709"><title>ROM Demand Paging limitations</title><p>The following are |
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30 known limitations for Demand Paging (using ROM demand paging) compared to |
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31 the other types of code paging: </p><ul> |
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32 <li><p>If the executable has static dependencies, then it is best to place |
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33 these dependencies in ROFS. This is a limitation of ROFS and not ROM demand |
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34 paging.</p></li> |
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35 <li><p>This paging system can only be used with files that are stored using |
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36 the ROM filing system. This is because ROM images using the ROM filing system |
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37 are designed to be executed in place. </p></li> |
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38 </ul> </section> |
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39 </conbody><related-links> |
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40 <link href="GUID-D6C2202C-778C-558A-97AA-649CD6DB5E87.dita"><linktext>ROFS File |
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41 System</linktext></link> |
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42 <link href="GUID-5A71755A-E67F-5007-8C55-5B8FA65B3C04.dita"><linktext>ROM File |
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43 System</linktext></link> |
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44 <link href="GUID-D666F9A0-8BFE-5067-BC76-C3AD73587195.dita"><linktext>Composite |
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45 File System</linktext></link> |
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46 <link href="GUID-903A9956-87E2-5191-87A3-6D40797EB820.dita"><linktext>Configuring |
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47 and building a ROM</linktext></link> |
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48 </related-links></concept> |