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| 1 | <?xml version="1.0" encoding="UTF-8"?> |
1 | <?xml version="1.0" encoding="UTF-8"?> |
| 2 | 2 | ||
| 3 | <chapter id="architecture"><?dbhtml filename="arch.html"?> |
3 | <chapter id="architecture"><?dbhtml filename="arch.html"?> |
| 4 | <title>Architecture overview</title> |
4 | <title>Architecture overview</title> |
| 5 | <section> |
5 | <section> |
| 6 | <title>Scheme</title> |
6 | <title>Scheme</title> |
| 7 | <para> |
7 | <para> |
| 8 | <mediaobject id="arch1"> |
8 | <mediaobject id="arch1"> |
| 9 | <imageobject role="html"> |
9 | <imageobject role="html"> |
| 10 | <imagedata format="PNG" fileref="images/arch1.png"/> |
10 | <imagedata format="PNG" fileref="images/arch1.png"/> |
| 11 | </imageobject> |
11 | </imageobject> |
| 12 | 12 | ||
| 13 | <imageobject role="fop"> |
13 | <imageobject role="fop"> |
| 14 | <imagedata format="SVG" fileref="images.vector/arch1.svg" /> |
14 | <imagedata format="SVG" fileref="images.vector/arch1.svg" /> |
| 15 | </imageobject> |
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| 16 | </mediaobject> |
16 | </mediaobject> |
| 17 | </para> |
17 | </para> |
| 18 | </section> |
18 | </section> |
| - | 19 | ||
| - | 20 | <section> |
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| - | 21 | <title>Monolithic microkernel</title> |
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| - | 22 | <para> |
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| - | 23 | Though HelenOS was initially planned as a microkernel, we where trying to avoid several issues, connected |
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| - | 24 | with microkernels, such as much higher overhead during memory management and hardware operations. For this reason |
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| - | 25 | some of the subsytems, that are to be implmented as servers in classic microkernel design, where implemented |
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| - | 26 | as a part of kernel, thus minimizing this overhead. |
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| - | 27 | </para> |
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| - | 28 | ||
| - | 29 | <formalpara> |
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| - | 30 | <title>Memory management</title> |
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| - | 31 | <para> |
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| - | 32 | Unlike the classic microkernel, HelenOS has all its memory management functionality in the kernel, available to the memory |
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| - | 33 | management server via the set of syscalls. |
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| - | 34 | </para> |
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| - | 35 | </formalpara> |
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| - | 36 | ||
| - | 37 | <formalpara> |
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| - | 38 | <title>Kernel device drivers</title> |
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| - | 39 | <para> |
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| - | 40 | HelenOS kernel has some of the very basic device drivers |
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| - | 41 | <itemizedlist> |
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| - | 42 | <listitem>ACPI</listitem> |
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| - | 43 | <listitem>APIC</listitem> |
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| - | 44 | <listitem>SMP configuration</listitem> |
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| - | 45 | <listitem>System clock</listitem> |
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| - | 46 | <listitem>Interrupt controllers</listitem> |
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| - | 47 | <listitem>Console</listitem> |
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| - | 48 | <listitem>VESA & frame buffer</listitem> |
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| - | 49 | </itemizedlist> |
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| - | 50 | ||
| - | 51 | </para> |
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| - | 52 | </formalpara> |
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| - | 53 | ||
| - | 54 | </section> |
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| - | 55 | ||
| - | 56 | <section> |
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| - | 57 | <title>Kernel primitives</title> |
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| - | 58 | <para> |
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| - | 59 | <termdef><glossterm>Thread</glossterm> is the basic execution primitive.</termdef> |
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| - | 60 | </para> |
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| - | 61 | ||
| - | 62 | <para> |
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| - | 63 | <termdef><glossterm>Thread context</glossterm> represents state of the <emphasis>thread</emphasis>. Contains registers state, FPU state, stack(s).</termdef> |
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| - | 64 | </para> |
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| - | 65 | ||
| - | 66 | <para> |
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| - | 67 | <termdef><glossterm>Task</glossterm> </termdef> |
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| - | 68 | </para> |
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| - | 69 | ||
| - | 70 | ||
| - | 71 | <para> |
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| - | 72 | <termdef> |
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| - | 73 | <glossterm>Address space area</glossterm> is a mutually disjunctive range of memory with the code, stack and data. |
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| - | 74 | </termdef> |
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| - | 75 | </para> |
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| - | 76 | ||
| - | 77 | <para> |
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| - | 78 | <termdef> |
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| - | 79 | <glossterm>Address space</glossterm> is a aggregating entity for address space areas, connecting them to the task. |
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| - | 80 | </termdef> |
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| - | 81 | </para> 1 |
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| - | 82 | </section> |
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| - | 83 | ||
| - | 84 | ||
| - | 85 | ||
| - | 86 | <section> |
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| - | 87 | <title>IPC</title> |
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| - | 88 | ||
| - | 89 | <para> |
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| - | 90 | Due to the high intertask communication traffic, IPC becomes critical subsystem for microkernels, putting high demands on the |
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| - | 91 | speed, latency and reliability of IPC model and implementation. HelenOS IPC is designed in analogy with telephone communication. |
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| - | 92 | Each task has an <emphasis>answerbox</emphasis> and a set of <emphasis>phones</emphasis> to call another tasks' answerboxes. Communication |
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| - | 93 | is possible after the link establishment, and can be either <emphasis>asynchronious</emphasis> or <emphasis>synchronious</emphasis>. |
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| - | 94 | </para> |
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| - | 95 | ||
| - | 96 | </section> |
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| - | 97 | ||
| - | 98 | ||
| 19 | <section> |
99 | <section> |
| 20 | <title>Task</title> |
- | |
| 21 | <para>Task ID - unique 64 bit number. Used for syscalls.</para> |
100 | <para>Task ID - unique 64 bit number. Used for syscalls.</para> |
| 22 | <para>Contains threads</para> |
101 | <para>Contains threads</para> |
| 23 | <para>Address space is created per task</para> |
102 | <para>Address space is created per task</para> |
| 24 | <para>Memory mapping is per task</para> |
103 | <para>Memory mapping is per task</para> |
| 25 | <para>Context per thread. (Note 2 stacks on IA64).</para> |
104 | <para>Context per thread. (Note 2 stacks on IA64).</para> |
| 26 | <para>IPC answer box associated per task</para> |
105 | <para>IPC answer box associated per task</para> |
| 27 | </section> |
106 | |
| 28 | <section> |
107 | |
| 29 | <title>Memory management</title> |
108 | <title>Memory management</title> |
| 30 | <para> |
109 | <para> |
| 31 | Zones - linked list (not many zones, so we can afford it. Can be replaced with B-tree in the future) |
110 | Zones - linked list (not many zones, so we can afford it. Can be replaced with B-tree in the future) |
| 32 | Number of zones depends on HW tables. Describe zone allocation/deallocation algoritm |
111 | Number of zones depends on HW tables. Describe zone allocation/deallocation algoritm |
| 33 | </para> |
112 | </para> |
| 34 | <para>Page tables. 4 level hierarchical and hash directly supported. B+ Tree can be implemented.</para> |
113 | <para>Page tables. 4 level hierarchical and hash directly supported. B+ Tree can be implemented.</para> |
| 35 | <para>For paging there is an abstract layer</para> |
114 | <para>For paging there is an abstract layer</para> |
| 36 | <para>TLB shootdown implementation (update TLB upon mapping update/remove). |
115 | <para>TLB shootdown implementation (update TLB upon mapping update/remove). |
| 37 | TLB shootdown ASID/ASID:PAGE/ALL. |
116 | TLB shootdown ASID/ASID:PAGE/ALL. |
| 38 | TLB shootdown requests can come in asynchroniously |
117 | TLB shootdown requests can come in asynchroniously |
| 39 | so there is a cache of TLB shootdown requests. Upon cache overflow TLB shootdown ALL is executed</para> |
118 | so there is a cache of TLB shootdown requests. Upon cache overflow TLB shootdown ALL is executed</para> |
| 40 | 119 | |
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| 41 | <para> |
120 | <para> |
| 42 | Address spaces. Address space area (B+ tree). Only for uspace. Set of syscalls (shrink/extend etc). |
121 | Address spaces. Address space area (B+ tree). Only for uspace. Set of syscalls (shrink/extend etc). |
| 43 | Special address space area type - device - prohibits shrink/extend syscalls to call on it. |
122 | Special address space area type - device - prohibits shrink/extend syscalls to call on it. |
| 44 | Address space has link to mapping tables (hierarchical - per Address space, hash - global tables). |
123 | Address space has link to mapping tables (hierarchical - per Address space, hash - global tables). |
| 45 | </para> |
124 | </para> |
| 46 | </section> |
125 | </section> |
| 47 | </chapter> |
126 | </chapter> |
| 48 | 127 | ||
| 49 | 128 | ||