From b91f1d19f234c6da2ad4795db625030be855c992 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <thomas@schwinge.name>
Date: Wed, 16 Feb 2011 10:11:16 +0100
Subject: microkernel/mach/gnumach/memory_management: New.

---
 microkernel/mach/gnumach/memory_management.mdwn | 36 +++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 microkernel/mach/gnumach/memory_management.mdwn

(limited to 'microkernel/mach/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)
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