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Date: Wed, 4 Apr 2007 16:06:24 -0700 (PDT)
From: Christoph Lameter <clameter@....com>
To: akpm@...ux-foundation.org
Cc: linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org,
Martin Bligh <mbligh@...gle.com>, linux-mm@...ck.org,
Andi Kleen <ak@...e.de>, Christoph Lameter <clameter@....com>,
Dave Hansen <hansendc@...ibm.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: [PATCH 2/4] x86_64: SPARSE_VIRTUAL 2M page size support
x86_64 implement SPARSE_VIRTUAL
x86_64 is using 2M page table entries to map its 1-1 kernel space.
We implement the virtual memmap also using 2M page table entries.
So there is no difference at all to FLATMEM. Both schemes require
a page table and a TLB for each 2MB. FLATMEM still references memory
since the mem_map pointer itself a variable. SPARSE_VIRTUAL uses a
constant for vmemmap. Thus no memory reference. SPARSE_VIRTUAL should
be superior to even FLATMEM.
With this SPARSEMEM becomes the most efficient way of handling
virt_to_page, pfn_to_page and friends for UP, SMP and NUMA on
x86_64.
Signed-off-by: Christoph Lameter <clameter@....com>
Index: linux-2.6.21-rc5-mm4/include/asm-x86_64/page.h
===================================================================
--- linux-2.6.21-rc5-mm4.orig/include/asm-x86_64/page.h 2007-04-03 18:41:06.000000000 -0700
+++ linux-2.6.21-rc5-mm4/include/asm-x86_64/page.h 2007-04-03 18:41:59.000000000 -0700
@@ -128,6 +128,7 @@ extern unsigned long phys_base;
VM_READ | VM_WRITE | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
#define __HAVE_ARCH_GATE_AREA 1
+#define vmemmap ((struct page *)0xffffe20000000000UL)
#include <asm-generic/memory_model.h>
#include <asm-generic/page.h>
Index: linux-2.6.21-rc5-mm4/Documentation/x86_64/mm.txt
===================================================================
--- linux-2.6.21-rc5-mm4.orig/Documentation/x86_64/mm.txt 2007-04-03 18:41:06.000000000 -0700
+++ linux-2.6.21-rc5-mm4/Documentation/x86_64/mm.txt 2007-04-03 18:41:59.000000000 -0700
@@ -9,6 +9,7 @@ ffff800000000000 - ffff80ffffffffff (=40
ffff810000000000 - ffffc0ffffffffff (=46 bits) direct mapping of all phys. memory
ffffc10000000000 - ffffc1ffffffffff (=40 bits) hole
ffffc20000000000 - ffffe1ffffffffff (=45 bits) vmalloc/ioremap space
+ffffe20000000000 - ffffe2ffffffffff (=40 bits) virtual memory map
... unused hole ...
ffffffff80000000 - ffffffff82800000 (=40 MB) kernel text mapping, from phys 0
... unused hole ...
Index: linux-2.6.21-rc5-mm4/arch/x86_64/Kconfig
===================================================================
--- linux-2.6.21-rc5-mm4.orig/arch/x86_64/Kconfig 2007-04-03 18:41:06.000000000 -0700
+++ linux-2.6.21-rc5-mm4/arch/x86_64/Kconfig 2007-04-03 18:41:59.000000000 -0700
@@ -392,6 +392,12 @@ config ARCH_SPARSEMEM_ENABLE
def_bool y
depends on (NUMA || EXPERIMENTAL)
+config SPARSE_VIRTUAL
+ def_bool y
+
+config ARCH_SUPPORTS_PMD_MAPPING
+ def_bool y
+
config ARCH_MEMORY_PROBE
def_bool y
depends on MEMORY_HOTPLUG
-
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