make PAGE_OFFSET config option on x86

PATCH New Dave Hansen 1 participant 1 message Aug 19, 2002

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Dave Hansen

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2002-08-19 20:33 UTC #0 lore raw

PATCH 1/1 make PAGE_OFFSET config option on x86

Whether they're a user that is doing a scientific application that needs more than 3GB, or a large PAE machine that needs more ZONE_NORMAL, lots of people are applying patches to change PAGE_OFFSET. This patch lets you do it in a config option. It is a port from Andrea's 2.4 tree, and I believe that Ingo is the original author.

Andrea's patch didn't have a Config.help entry for this option, so I wrote one. I may not have all of the necessary context to explain it, so any comments there would be appreciated.

Signature · 2 lines

Dave Hansen
[email protected]

# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher. # This patch includes the following deltas:
# ChangeSet 1.489 -> 1.491
# include/asm-i386/processor.h 1.28 -> 1.29
# arch/i386/Config.help 1.12 -> 1.13
# include/asm-i386/page.h 1.15 -> 1.16
# arch/i386/vmlinux.lds 1.9 -> (deleted)

#	 arch/i386/config.in	1.46    -> 1.47   
#	  arch/i386/Makefile	1.16    -> 1.17   
#	          Rules.make	1.68    -> 1.69   
#	         mm/memory.c	1.83    -> 1.85   
#	               (new)	        -> 1.1     arch/i386/vmlinux.lds.S
#	               (new)	        -> 1.1     include/asm-i386/page_offset.h

#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/08/19 haveblue@elm3b96.(none) 1.490

# merge Andrea's PAGE_OFFSET configuration option
# --------------------------------------------
# 02/08/19	haveblue@elm3b96.(none)	1.491
# fix merge bug
# 
# add Config.help entry
# --------------------------------------------
#
diff -Nru a/Rules.make b/Rules.make
--- a/Rules.make	Mon Aug 19 13:28:19 2002
+++ b/Rules.make	Mon Aug 19 13:28:19 2002
@@ -149,12 +149,29 @@
 #
 # Added the SMP separator to stop module accidents between uniprocessor
 # and SMP Intel boxes - AC - from bits by Michael Chastain
+# Added separator for different PAGE_OFFSET memory models - Ingo.
 #

ifdef CONFIG_SMP
genksyms_smp_prefix := -p smp_
else
genksyms_smp_prefix :=
+endif
+
+ifdef CONFIG_2GB
+ifdef CONFIG_SMP
+ genksyms_smp_prefix := -p smp_2gig_
+else
+ genksyms_smp_prefix := -p 2gig_
+endif
+endif
+
+ifdef CONFIG_3GB
+ifdef CONFIG_SMP
+ genksyms_smp_prefix := -p smp_3gig_
+else
+ genksyms_smp_prefix := -p 3gig_
+endif
endif

# Don't include modversions.h, we're just about to generate it here.

arch/i386/Config.help +21 -0

diff -Nru a/arch/i386/Config.help b/arch/i386/Config.help
@@ -128,6 +128,27 @@
 
   If unsure, say "off".
 
+CONFIG_1GB
+  On i386, a process can only virtually address 4GB of memory.  This
+  lets you select how much of that virtual space you would like to 
+  devoted to userspace, and how much to the kernel.  
+  
+  Some userspace programs would like to address as much as possible and 
+  have few demands of the kernel other than it get out of the way.  These
+  users may opt to use the 3.5GB option to give their userspace program 
+  as much room as possible.  Due to alignment issues imposed by PAE, 
+  the "3.5GB" option is unavailable if "64GB" high memory support is 
+  enabled.
+
+  Other users (especially those who use PAE) may be running out of
+  ZONE_NORMAL memory.  Those users may benefit from increasing the
+  kernel's virtual address space size by taking it away from userspace, 
+  which may not need all of its space.  An indicator that this is 
+  happening is when /proc/Meminfo's "LowFree:" is a small percentage of
+  "LowTotal:" while "HighFree:" is very large.
+
+  If unsure, say "3GB"
+  
 CONFIG_HIGHPTE
   The VM uses one page table entry for each page of physical memory.
   For systems with a lot of RAM, this can be wasteful of precious

arch/i386/Makefile +4 -0

diff -Nru a/arch/i386/Makefile b/arch/i386/Makefile
@@ -104,6 +104,9 @@
 
 MAKEBOOT = +$(MAKE) -C arch/$(ARCH)/boot
 
+arch/i386/vmlinux.lds: arch/i386/vmlinux.lds.S FORCE
+	$(CPP) -C -P -I$(HPATH) -imacros $(HPATH)/asm-i386/page_offset.h -Ui386 arch/i386/vmlinux.lds.S >arch/i386/vmlinux.lds
+
 vmlinux: arch/i386/vmlinux.lds
 
 .PHONY: zImage bzImage compressed zlilo bzlilo zdisk bzdisk install \

@@ -141,3 +144,4 @@
 	@$(MAKEBOOT) clean
 
 archmrproper:
+	rm -f arch/i386/vmlinux.lds

arch/i386/config.in +12 -2

diff -Nru a/arch/i386/config.in b/arch/i386/config.in
@@ -186,14 +186,24 @@
 	 4GB           CONFIG_HIGHMEM4G \
 	 64GB          CONFIG_HIGHMEM64G" off
 
-if [ "$CONFIG_HIGHMEM4G" = "y" ]; then
+if [ "$CONFIG_HIGHMEM4G" = "y" -o "$CONFIG_HIGHMEM64G" = "y" ]; then
    define_bool CONFIG_HIGHMEM y
 fi
 
 if [ "$CONFIG_HIGHMEM64G" = "y" ]; then
-   define_bool CONFIG_HIGHMEM y
    define_bool CONFIG_X86_PAE y
+   choice 'User address space size' \
+	"3GB		CONFIG_1GB \
+	 2GB		CONFIG_2GB \
+	 1GB		CONFIG_3GB" 3GB
+else
+   choice 'User address space size' \
+	"3GB		CONFIG_1GB \
+ 	 2GB		CONFIG_2GB \
+	 1GB		CONFIG_3GB \
+	 3.5GB		CONFIG_05GB" 3GB
 fi
+	 
 
 bool 'Math emulation' CONFIG_MATH_EMULATION
 bool 'MTRR (Memory Type Range Register) support' CONFIG_MTRR

arch/i386/vmlinux.lds deleted +0 ~~-101~~

101 lines not on this page · raw message

arch/i386/vmlinux.lds.S new file +101 -0

101 lines not on this page · raw message

include/asm-i386/page.h +3 -1

diff -Nru a/include/asm-i386/page.h b/include/asm-i386/page.h
@@ -81,7 +81,9 @@
  * and CONFIG_HIGHMEM64G options in the kernel configuration.
  */
 
-#define __PAGE_OFFSET		(0xC0000000)
+#include <asm/page_offset.h>
+
+#define __PAGE_OFFSET		(PAGE_OFFSET_RAW)
 
 /*
  * This much address space is reserved for vmalloc() and iomap()

include/asm-i386/page_offset.h new file +10 -0

diff -Nru a/include/asm-i386/page_offset.h b/include/asm-i386/page_offset.h
@@ -0,0 +1,10 @@
+#include <linux/config.h>
+#ifdef CONFIG_05GB
+#define PAGE_OFFSET_RAW 0xE0000000
+#elif defined(CONFIG_1GB)
+#define PAGE_OFFSET_RAW 0xC0000000
+#elif defined(CONFIG_2GB)
+#define PAGE_OFFSET_RAW 0x80000000
+#elif defined(CONFIG_3GB)
+#define PAGE_OFFSET_RAW 0x40000000
+#endif

include/asm-i386/processor.h +4 -0

diff -Nru a/include/asm-i386/processor.h b/include/asm-i386/processor.h
@@ -270,7 +270,11 @@
 /* This decides where the kernel will search for a free chunk of vm
  * space during mmap's.
  */
+#ifndef CONFIG_05GB
 #define TASK_UNMAPPED_BASE	(TASK_SIZE / 3)
+#else
+#define TASK_UNMAPPED_BASE	(TASK_SIZE / 16)
+#endif
 
 /*
  * Size of io_bitmap in longwords: 32 is ports 0-0x3ff.

mm/memory.c +18 -5

diff -Nru a/mm/memory.c b/mm/memory.c
@@ -97,8 +97,7 @@
 
 static inline void free_one_pgd(mmu_gather_t *tlb, pgd_t * dir)
 {
-	int j;
-	pmd_t * pmd;
+	pmd_t * pmd, * md, * emd;
 
 	if (pgd_none(*dir))
 		return;

@@ -109,9 +108,23 @@
 	}
 	pmd = pmd_offset(dir, 0);
 	pgd_clear(dir);
-	for (j = 0; j < PTRS_PER_PMD ; j++) {
-		prefetchw(pmd+j+(PREFETCH_STRIDE/16));
-		free_one_pmd(tlb, pmd+j);
+
+	/*
+ 	 * Beware if changing the loop below.  It once used int j,
+	 *	for (j = 0; j < PTRS_PER_PMD; j++)
+	 *		free_one_pmd(pmd+j);
+	 * but some older i386 compilers (e.g. egcs-2.91.66, gcc-2.95.3)
+	 * terminated the loop with a _signed_ address comparison
+	 * using "jle", when configured for HIGHMEM64GB (X86_PAE).
+	 * If also configured for 3GB of kernel virtual address space,
+	 * if page at physical 0x3ffff000 virtual 0x7ffff000 is used as
+	 * a pmd, when that mm exits the loop goes on to free "entries"
+	 * found at 0x80000000 onwards.  The loop below compiles instead
+	 * to be terminated by unsigned address comparison using "jb".
+	 */
+	for (md = pmd, emd = pmd + PTRS_PER_PMD; md < emd; md++) {
+		prefetchw(md+(PREFETCH_STRIDE/16));
+		free_one_pmd(tlb,md);
 	}
 	pmd_free_tlb(tlb, pmd);
 }