16,87 → 16,8 |
</mediaobject> |
</para> |
</section> |
|
<section> |
<title>Monolithic microkernel</title> |
<para> |
Though HelenOS was initially planned as a microkernel, we where trying to avoid several issues, connected |
with microkernels, such as much higher overhead during memory management and hardware operations. For this reason |
some of the subsytems, that are to be implmented as servers in classic microkernel design, where implemented |
as a part of kernel, thus minimizing this overhead. |
</para> |
|
<formalpara> |
<title>Memory management</title> |
<para> |
Unlike the classic microkernel, HelenOS has all its memory management functionality in the kernel, available to the memory |
management server via the set of syscalls. |
</para> |
</formalpara> |
|
<formalpara> |
<title>Kernel device drivers</title> |
<para> |
HelenOS kernel has some of the very basic device drivers |
<itemizedlist> |
<listitem>ACPI</listitem> |
<listitem>APIC</listitem> |
<listitem>SMP configuration</listitem> |
<listitem>System clock</listitem> |
<listitem>Interrupt controllers</listitem> |
<listitem>Console</listitem> |
<listitem>VESA & frame buffer</listitem> |
</itemizedlist> |
|
</para> |
</formalpara> |
|
</section> |
|
<section> |
<title>Kernel primitives</title> |
<para> |
<termdef><glossterm>Thread</glossterm> is the basic execution primitive.</termdef> |
</para> |
|
<para> |
<termdef><glossterm>Thread context</glossterm> represents state of the <emphasis>thread</emphasis>. Contains registers state, FPU state, stack(s).</termdef> |
</para> |
|
<para> |
<termdef><glossterm>Task</glossterm> </termdef> |
</para> |
|
|
<para> |
<termdef> |
<glossterm>Address space area</glossterm> is a mutually disjunctive range of memory with the code, stack and data. |
</termdef> |
</para> |
|
<para> |
<termdef> |
<glossterm>Address space</glossterm> is a aggregating entity for address space areas, connecting them to the task. |
</termdef> |
</para> 1 |
</section> |
|
|
|
<section> |
<title>IPC</title> |
|
<para> |
Due to the high intertask communication traffic, IPC becomes critical subsystem for microkernels, putting high demands on the |
speed, latency and reliability of IPC model and implementation. HelenOS IPC is designed in analogy with telephone communication. |
Each task has an <emphasis>answerbox</emphasis> and a set of <emphasis>phones</emphasis> to call another tasks' answerboxes. Communication |
is possible after the link establishment, and can be either <emphasis>asynchronious</emphasis> or <emphasis>synchronious</emphasis>. |
</para> |
|
</section> |
|
|
<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> |
103,8 → 24,8 |
<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) |