| 1,48 → 1,69 |
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| <?xml version="1.0" encoding="UTF-8"?> |
| <chapter id="mm"> |
| <?dbhtml filename="mm.html"?> |
| |
| <title>Memory management</title> |
| |
| <chapter> |
| <title>Memory management</title> |
| <section> |
| <title>Virtual memory management</title> |
| |
| <section> |
| <title>Virtual memory management</title> |
| <title>Address spaces</title> |
| |
| <para></para> |
| </section> |
| |
| <section> |
| <title>Physical memory management</title> |
| <title>Virtual address translation</title> |
| |
| <para></para> |
| </section> |
| </section> |
| |
| <section> |
| <title>Kernel allocators</title> |
| <section> |
| <title>Physical memory management</title> |
| |
| <section id="zones_and_frames"> |
| <title>Zones and frames</title> |
| |
| <para>Physical memory is divided into zones. Each zone represents |
| continuous area of physical memory frames. Allocation of frames is |
| handled by the <link linkend="buddy_allocator">buddy allocator</link> |
| associated with the zone. Zone also contains information about free and |
| occupied frames and its base addresss in the memory. Some of the |
| architectures (Mips, PPC) have only one zone, that covers whole physical |
| memory. Other architectures (IA32) have multiple zones.</para> |
| </section> |
| |
| <section> |
| <title>Buddy allocator</title> |
| <section id="buddy_allocator"> |
| <title>Buddy allocator</title> |
| |
| <para>Physical memory allocation is handled by buddy allocator.</para> |
| </section> |
| <para>Physical memory allocation inside one <link |
| linkend="zones_and_frames">memory zone</link> is being handled by buddy |
| allocation system. This approach greatly reduces possibility of memory |
| fragmentation and helps in allocating bigger continious blocks of |
| physical memory aligned to their size.</para> |
| |
| <section> |
| <title>Slab allocator</title> |
| </section> |
| <graphic fileref="images/mm1.png" /> |
| |
| <para>Frames are grouped into bigger blocks and blocks of the size i ^ 2 |
| are stored in the list indexed with <varname>i</varname> (so called |
| order index). If list contains 2 ajacent blocks (of a same size of |
| cause) they can be merged into the bigger one and moved into the list |
| with higher order index, thus making possible allocation of a bigger |
| block.</para> |
| </section> |
| |
| |
| <section> |
| <title>Memory sharing</title> |
| <title>Slab allocator</title> |
| |
| <para></para> |
| <para>Kernel memory allocation is handled by slab.</para> |
| </section> |
| </section> |
| |
| <section> |
| <title>Memory sharing</title> |
| |
| |
| |
| </chapter> |
| |
| |
| |
| <para>Not implemented yet(?)</para> |
| </section> |
| </chapter> |