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| /design/trunk/src/ch_arch_overview.xml |
|---|
| 1,150 → 1,156 |
| <?xml version="1.0" encoding="UTF-8"?> |
| <chapter id="architecture"> |
| <?dbhtml filename="arch.html"?> |
| <chapter id="architecture"><?dbhtml filename="arch.html"?> |
| <title>Architecture overview</title> |
| <section> |
| <title>Scheme</title> |
| <para> |
| <mediaobject id="arch1"> |
| <imageobject role="html"> |
| <imagedata format="PNG" fileref="images/arch1.png"/> |
| </imageobject> |
| <imageobject role="fop"> |
| <imagedata format="SVG" fileref="images.vector/arch1.svg" /> |
| </imageobject> |
| </mediaobject> |
| </para> |
| </section> |
| <title>Architecture overview</title> |
| <section> |
| <title>Kernel primitives</title> |
| <para> |
| <termdef><glossterm>Thread</glossterm> is the basic execution primitive.</termdef> |
| </para> |
| <section> |
| <title>Scheme</title> |
| <para> |
| <termdef><glossterm>Thread context</glossterm> represents state of the <emphasis>thread</emphasis>. |
| Thread context is built of the context registers contents, FPU state and the stack.</termdef> |
| </para> |
| <para><mediaobject id="arch1"> |
| <imageobject role="html"> |
| <imagedata fileref="images/arch1.png" format="PNG" /> |
| </imageobject> |
| <para> |
| <termdef> |
| <glossterm>Task</glossterm> is a multi-purpose entity, serving to |
| <itemizedlist> |
| <listitem>incorporate set if its threads</listitem> |
| <listitem>provide common address space to its threads</listitem> |
| <listitem>be an end-point in IPC</listitem> |
| </itemizedlist> |
| <imageobject role="fop"> |
| <imagedata fileref="images.vector/arch1.svg" format="SVG" /> |
| </imageobject> |
| </mediaobject></para> |
| </section> |
| </termdef> |
| </para> |
| <para> |
| <termdef> |
| <glossterm>Address space area</glossterm> is a mutually disjunctive range of memory with the code, stack and data. |
| </termdef> |
| </para> |
| <section> |
| <title>Kernel primitives</title> |
| <para> |
| <termdef> |
| <glossterm>Address space</glossterm> is a aggregating entity for address space areas, connecting them to the task. |
| </termdef> |
| </para> |
| </section> |
| <para><termdef><glossterm>Thread</glossterm> is the basic execution |
| primitive.</termdef></para> |
| <section> |
| <title>Monolithic microkernel</title> |
| <para> |
| Though HelenOS was initially planned as a microkernel, we were 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 subsystems, that are to be implemented as servers in classic microkernel design, were implemented |
| as a part of kernel, thus minimizing this overhead. |
| </para> |
| <para><termdef><glossterm>Thread context</glossterm> represents state of |
| the <emphasis>thread</emphasis>. Thread context is built of the context |
| registers contents, FPU state and the stack.</termdef></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> |
| <para><termdef> <glossterm>Task</glossterm> is a multi-purpose entity, |
| serving to <itemizedlist> |
| <listitem>incorporate set if its threads</listitem> |
| <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> |
| <listitem>provide common address space to its threads</listitem> |
| </para> |
| </formalpara> |
| <listitem>be an end-point in IPC</listitem> |
| </itemizedlist> </termdef></para> |
| </section> |
| <para><termdef> <glossterm>Address space area</glossterm> is a mutually |
| disjunctive range of memory with the code, stack and data. |
| </termdef></para> |
| <section> |
| <title>IPC</title> |
| <para><termdef> <glossterm>Address space</glossterm> is a aggregating |
| entity for address space areas, connecting them to the task. |
| </termdef></para> |
| </section> |
| <para>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. |
| </para> |
| <para>Communication |
| is possible after the connection is established, and can be either <emphasis>asynchronious</emphasis> or <emphasis>synchronious</emphasis>. |
| </para> |
| </section> |
| <section> |
| <title>Monolithic microkernel</title> |
| <section> |
| <title>Functionality model</title> |
| <para>Though HelenOS was initially planned as a microkernel, we were |
| 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 subsystems, that are to be implemented as servers in |
| classic microkernel design, were implemented as a part of kernel, thus |
| minimizing this overhead.</para> |
| <para> |
| As you know, microkernel design is very simple, just enough to provide communication facility for tasks. Most of the OS functionality |
| is performed by server tasks, that are running in userspace. |
| Thus most of the system calls in monolithic kernels, are the IPC calls on server tasks in microkernels. |
| </para> |
| <para> |
| Moreover, problems experience the device drivers. Running in the user space, device driver still needs to recieve interrupts |
| and access hardware directly. |
| </para> |
| <para> |
| This raises two major problems in microkernels: |
| <orderedlist numeration="loweralpha"> |
| <listitem>What is the recipient address of the server (e.g. "memory manager" or a specific device driver) ?</listitem> |
| <listitem>How this server task is going to access hardware or kernel while running in the user mode?</listitem> |
| </orderedlist> |
| </para> |
| <formalpara id="intro_ns"> |
| <title>Name server</title> |
| <para>As every microkernel, HelenOS has a "Name server" task with "well known" IPC address, that connects user task to any server |
| just by the string service indentification.</para> |
| </formalpara> |
| <formalpara id="intro_ddi"> |
| <title>Device driver interface</title> |
| <para>Device drivers use special syscalls to map physical memory areas into their address space, to map port regions (mostly ia32). |
| Interrupts are delivered to the device driver task by the standard IPC means. |
| </para> |
| </formalpara> |
| </section> |
| <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> |
| </chapter> |
| <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>IPC</title> |
| <para>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.</para> |
| <para>Communication is possible after the connection is established, and |
| can be either <emphasis>asynchronious</emphasis> or |
| <emphasis>synchronious</emphasis>.</para> |
| </section> |
| <section> |
| <title>Functionality model</title> |
| <para>As you know, microkernel design is very simple, just enough to |
| provide communication facility for tasks. Most of the OS functionality is |
| performed by server tasks, that are running in userspace. Thus most of the |
| system calls in monolithic kernels, are the IPC calls on server tasks in |
| microkernels.</para> |
| <para>Moreover, problems experience the device drivers. Running in the |
| user space, device driver still needs to recieve interrupts and access |
| hardware directly.</para> |
| <para>This raises two major problems in microkernels: <orderedlist |
| numeration="loweralpha"> |
| <listitem> |
| What is the recipient address of the server (e.g. "memory manager" or a specific device driver) ? |
| </listitem> |
| <listitem> |
| How this server task is going to access hardware or kernel while running in the user mode? |
| </listitem> |
| </orderedlist></para> |
| <formalpara id="intro_ns"> |
| <title>Name server</title> |
| <para>As every microkernel, HelenOS has a "Name server" task with "well |
| known" IPC address, that connects user task to any server just by the |
| string service indentification.</para> |
| </formalpara> |
| <formalpara id="intro_ddi"> |
| <title>Device driver interface</title> |
| <para>Device drivers use special syscalls to map physical memory areas |
| into their address space, to map port regions (mostly ia32). Interrupts |
| are delivered to the device driver task by the standard IPC |
| means.</para> |
| </formalpara> |
| </section> |
| </chapter> |
| /design/trunk/src/ch_memory_management.xml |
|---|
| 24,10 → 24,9 |
| Allowing, in general, to load and execute two programs that are linked on the same address without complicated relocations. |
| </listitem> |
| </itemizedlist></para> |
| <para><!-- |
| <para><!-- |
| 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 |
| 43,23 → 42,19 |
| </section> |
| <section> |
| <title>Paging</title> |
| <para>Virtual memory is usually using paged memory model, where virtual |
| memory address space is divided into the <emphasis>pages</emphasis> |
| (usually having size 4096 bytes) and physical memory is divided into the |
| frames (same sized as a page, of course). Each page may be mapped to some |
| frame and then, upon memory access to the virtual address, CPU performs |
| <emphasis>address translation</emphasis> during the instruction |
| frames (same sized as a page, of course). Each page may be mapped to |
| some frame and then, upon memory access to the virtual address, CPU |
| performs <emphasis>address translation</emphasis> during the instruction |
| execution. Non-existing mapping generates page fault exception, calling |
| kernel exception handler, thus allowing kernel to manipulate rules of |
| memory access. Information for pages mapping is stored by kernel in the |
| <link linkend="page_tables">page tables</link></para> |
| <para>The majority of the architectures use multi-level page tables, |
| which means need to access physical memory several times before getting |
| physical address. This fact would make serios performance overhead in |
| 66,11 → 61,11 |
| virtual memory management. To avoid this <link linkend="tlb">Traslation |
| Lookaside Buffer (TLB)</link> is used.</para> |
| <para>At the moment HelenOS does not support swapping.</para> |
| <para>- pouzivame vypadky stranky k alokaci ramcu on-demand v ramci as_area - na architekturach, ktere to podporuji, podporujeme non-exec stranky </para> |
| <para>- pouzivame vypadky stranky k alokaci ramcu on-demand v ramci |
| as_area - na architekturach, ktere to podporuji, podporujeme non-exec |
| stranky</para> |
| </section> |
| <section> |
| 79,15 → 74,11 |
| <section> |
| <title>Address spaces and areas</title> |
| <para> |
| - adresovy prostor se sklada z tzv. address space areas |
| <para>- adresovy prostor se sklada z tzv. address space areas |
| usporadanych v B+stromu; tyto areas popisuji vyuzivane casti |
| adresoveho prostoru patrici do user address space. Kazda cast je dana |
| svoji bazovou adresou, velikosti a flagy (rwx/dd). |
| svoji bazovou adresou, velikosti a flagy (rwx/dd).</para> |
| </para> |
| <para>- uzivatelske thready maji moznost manipulovat se svym adresovym |
| prostorem (vytvaret/resizovat/sdilet) as_areas pomoci syscallu</para> |
| </section> |
| 116,9 → 107,6 |
| a neni ani nijak osetrena. Tim padem plati, ze kazdy task ma vlastni |
| adresovy prostor</para> |
| </section> |
| </section> |
| <section> |
| 221,6 → 209,16 |
| <section id="frame_allocator"> |
| <title>Frame allocator</title> |
| <para><mediaobject id="frame_alloc"> |
| <imageobject role="html"> |
| <imagedata fileref="images/frame_alloc.png" format="PNG" /> |
| </imageobject> |
| <imageobject role="fop"> |
| <imagedata fileref="images.vector/frame_alloc.svg" format="SVG" /> |
| </imageobject> |
| </mediaobject></para> |
| <formalpara> |
| <title>Overview</title> |
| 262,6 → 260,16 |
| <section> |
| <title>Overview</title> |
| <para><mediaobject id="buddy_alloc"> |
| <imageobject role="html"> |
| <imagedata fileref="images/buddy_alloc.png" format="PNG" /> |
| </imageobject> |
| <imageobject role="fop"> |
| <imagedata fileref="images.vector/buddy_alloc.svg" format="SVG" /> |
| </imageobject> |
| </mediaobject></para> |
| <para>In buddy allocator, memory is broken down into power-of-two |
| sized naturally aligned blocks. These blocks are organized in an array |
| of lists in which list with index i contains all unallocated blocks of |
| 301,8 → 309,8 |
| implementation of this interface, the buddy allocator can use |
| specialized external functions to find buddy for a block, split and |
| coalesce blocks, manipulate block order and mark blocks busy or |
| available. For precize documentation of this interface, refer to <link |
| linkend="???">HelenOS Generic Kernel Reference Manual</link>.</para> |
| available. For precize documentation of this interface, refer to |
| <emphasis>"HelenOS Generic Kernel Reference Manual"</emphasis>.</para> |
| <formalpara> |
| <title>Data organization</title> |
| 394,6 → 402,16 |
| <section> |
| <title>Implementation</title> |
| <para><mediaobject id="slab_alloc"> |
| <imageobject role="html"> |
| <imagedata fileref="images/slab_alloc.png" format="PNG" /> |
| </imageobject> |
| <imageobject role="fop"> |
| <imagedata fileref="images.vector/slab_alloc.svg" format="SVG" /> |
| </imageobject> |
| </mediaobject></para> |
| <para>The SLAB allocator is closely modelled after <ulink |
| url="http://www.usenix.org/events/usenix01/full_papers/bonwick/bonwick_html/"> |
| OpenSolaris SLAB allocator by Jeff Bonwick and Jonathan Adams </ulink> |
