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<?xml version="1.0" encoding="UTF-8"?>
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<chapter id="mm">
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  <?dbhtml filename="mm.html"?>
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  <title>Memory management</title>
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  <section>
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    <title>Virtual memory management</title>
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    <section>
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      <title>Address spaces</title>
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      <para></para>
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    </section>
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    <section>
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      <title>Virtual address translation</title>
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      <para></para>
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    </section>
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  </section>
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  <section>
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    <title>Physical memory management</title>
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    <section id="zones_and_frames">
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      <title>Zones and frames</title>
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      <para>Physical memory is divided into zones. Each zone represents
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      continuous area of physical memory frames. Allocation of frames is
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      handled by the <link linkend="buddy_allocator">buddy allocator</link>
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      associated with the zone. Zone also contains information about free and
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      occupied frames and its base addresss in the memory. Some of the
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      architectures (Mips, PPC) have only one zone, that covers whole physical
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      memory. Other architectures (IA32) have multiple zones.</para>
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    </section>
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    <section id="buddy_allocator">
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      <title>Buddy allocator</title>
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      <para>Physical memory allocation inside one <link
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      linkend="zones_and_frames">memory zone</link> is being handled by buddy
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      allocation system. This approach greatly reduces possibility of memory
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      fragmentation and helps in allocating bigger continious blocks of
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      physical memory aligned to their size.</para>
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      <graphic fileref="images/mm1.png" />
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      <para>Frames are grouped into bigger blocks and blocks of the size i ^ 2
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      are stored in the list indexed with <varname>i</varname> (so called
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      order index). If list contains 2 ajacent blocks (of a same size of
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      cause) they can be merged into the bigger one and moved into the list
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      with higher order index, thus making possible allocation of a bigger
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      block.</para>
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    </section>
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    <section>
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      <title>Slab allocator</title>
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      <para>Kernel memory allocation is handled by slab.</para>
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    </section>
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  </section>
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  <section>
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    <title>Memory sharing</title>
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    <para>Not implemented yet(?)</para>
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  </section>
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</chapter>