microkernel/mach/gnumach/memory_management: New.

2 files changed, 41 insertions, 4 deletions

diff --git a/microkernel/mach/gnumach.mdwn b/microkernel/mach/gnumach.mdwn
index f3d6d5f9..b385ca09 100644
--- a/microkernel/mach/gnumach.mdwn
+++ b/microkernel/mach/gnumach.mdwn
@@ -1,13 +1,13 @@
-[[!meta copyright="Copyright © 2001, 2002, 2007, 2008 Free Software Foundation,
-Inc."]]
+[[!meta copyright="Copyright © 2001, 2002, 2007, 2008, 2011 Free Software
+Foundation, Inc."]]
 
 [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
 id="license" text="Permission is granted to copy, distribute and/or modify this
 document under the terms of the GNU Free Documentation License, Version 1.2 or
 any later version published by the Free Software Foundation; with no Invariant
 Sections, no Front-Cover Texts, and no Back-Cover Texts.  A copy of the license
-is included in the section entitled
-[[GNU Free Documentation License|/fdl]]."]]"""]]
+is included in the section entitled [[GNU Free Documentation
+License|/fdl]]."]]"""]]
 
 GNU Mach is the microkernel that the [[GNU_Hurd|hurd]] system is based on.
 
@@ -75,6 +75,7 @@ GNU/Hurd.
   * [[Building]]
   * [[Debugging]]
   * [[Boot_Trace]]
+  * [[Memory_Management]]
   * [[Projects]]
       * [[Rules]]
       * [[Open Issues|tag/open_issue_gnumach]]
diff --git a/microkernel/mach/gnumach/memory_management.mdwn b/microkernel/mach/gnumach/memory_management.mdwn
new file mode 100644
index 00000000..49a082e9
--- /dev/null
+++ b/microkernel/mach/gnumach/memory_management.mdwn
@@ -0,0 +1,36 @@
+[[!meta copyright="Copyright © 2011 Free Software Foundation, Inc."]]
+
+[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
+id="license" text="Permission is granted to copy, distribute and/or modify this
+document under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no Invariant
+Sections, no Front-Cover Texts, and no Back-Cover Texts.  A copy of the license
+is included in the section entitled [[GNU Free Documentation
+License|/fdl]]."]]"""]]
+
+IRC, freenode, #hurd, 2011-02-15
+
+    <braunr> etenil: originally, mach had its own virtual space (the kernel
+      space)
+    <braunr> etenil: in order to use linux 2.0 drivers, it now directly maps
+      physical memory, as linux does
+    <braunr> etenil: but there is nothing similar to kmap() or vmalloc() in
+      mach, so the kernel is limited to its 1 GiB
+    <braunr> (3 GiB userspace / 1 GiB kernelspace)
+    <braunr> that's the short version, there is a vmalloc() in mach, but this
+      trick made it behave almost like a kmalloc()
+    <antrik> braunr: the direct mapping is *only* for the benefit of Linux
+      drivers?...
+    <braunr> also, the configuration of segments limits the kernel space
+    <braunr> antrik: i'm not sure, as i said, this is the short version
+    <braunr> antrik: but there is a paper which describes the integration of
+      those drivers in mach
+    <etenil> you mean the linux 2.0 drivers?
+    <antrik> braunr: I read it once, but I don't remember anything about the
+      physical mapping in there...
+    <antrik> etenil: well, originally it was 1.3, but essentially that's the
+      same...
+    <braunr> i don't see any other reason why there would be a direct mapping
+    <braunr> except for performance (because you can use larger - even very
+      lage - pages without resetting the mmu often thanks to global pages, but
+      that didn't exist at the time)