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<chapter id="architecture"><?dbhtml filename="arch.html"?>
<title>Architecture overview</title>
<section>
<title>Task</title>
<para>Task ID - unique 64 bit number. Used for syscalls.</para>
<para>Contains threads</para>
<para>Address space is created per task</para>
<para>Memory mapping is per task</para>
<para>Context per thread. (Note 2 stacks on IA64).</para>
<para>IPC answer box associated per task</para>
</section>
<section>
<title>Memory management</title>
<para>
Zones - linked list (not many zones, so we can afford it. Can be replaced with B-tree in the future)
Number of zones depends on HW tables. Describe zone allocation/deallocation algoritm
</para>
<para>Page tables. 4 level hierarchical and hash directly supported. B+ Tree can be implemented.
<para>For paging there is an abstract layer</para>
<para>TLB shootdown implementation (update TLB upon mapping update/remove).
TLB shootdown ASID/ASID:PAGE/ALL.
TLB shootdown requests can come in asynchroniously
so there is a cache of TLB shootdown requests. Upon cache overflow TLB shootdown ALL is executed</para>
<para>
Address spaces. Address space area (B+ tree). Only for uspace. Set of syscalls (shrink/extend etc).
Special address space area type - device - prohibits shrink/extend syscalls to call on it.
Address space has link to mapping tables (hierarchical - per Address space, hash - global tables).
</para>
</chapter>