From: Michael Frank <mhf@linuxmail.org>
Enclosed is a patch for x86 to make highmem= option easier to use.
- Automates alignment of highmem zone
- Fixes invalid highmem settings whether too small or to large
- Adds entry in kernel-parameters.txt
- Permits highmem emulation, so people with less than 896MB of memory can
test CONFIG_HIGHMEM. Highmem emulation can be used on any machine with at
least 72MB RAM.
The patch does not add to bloat as it is part of __init code.
---
Documentation/kernel-parameters.txt | 8 +++
arch/i386/kernel/setup.c | 91 +++++++++++++++++++++++++++---------
2 files changed, 77 insertions(+), 22 deletions(-)
diff -puN arch/i386/kernel/setup.c~highmem-equals-user-friendliness arch/i386/kernel/setup.c
--- 25/arch/i386/kernel/setup.c~highmem-equals-user-friendliness 2004-02-09 00:14:08.000000000 -0800
+++ 25-akpm/arch/i386/kernel/setup.c 2004-02-09 00:14:08.000000000 -0800
@@ -588,9 +588,12 @@ static void __init parse_cmdline_early (
#endif /* CONFIG_ACPI_BOOT */
/*
- * highmem=size forces highmem to be exactly 'size' bytes.
+ * highmem=size forces highmem to be at most 'size' bytes.
* This works even on boxes that have no highmem otherwise.
* This also works to reduce highmem size on bigger boxes.
+ *
+ * Note: highmem sise is adjusted downward for proper zone
+ * alignment of the highmem physical start address.
*/
if (c == ' ' && !memcmp(from, "highmem=", 8))
highmem_pages = memparse(from+8, &from) >> PAGE_SHIFT;
@@ -657,6 +660,11 @@ void __init find_max_pfn(void)
/*
* Determine low and high memory ranges:
*/
+
+#define ZONE_REQUIRED_PAGE_ALIGNMENT (1UL << (MAX_ORDER-1))
+#define ZONE_REQUIRED_PAGE_ALIGNMENT_MASK (ZONE_REQUIRED_PAGE_ALIGNMENT-1)
+#define PAGES_FOR_64MB (64*1024*1024/PAGE_SIZE)
+
unsigned long __init find_max_low_pfn(void)
{
unsigned long max_low_pfn;
@@ -668,14 +676,16 @@ unsigned long __init find_max_low_pfn(vo
if (highmem_pages + MAXMEM_PFN < max_pfn)
max_pfn = MAXMEM_PFN + highmem_pages;
if (highmem_pages + MAXMEM_PFN > max_pfn) {
- printk("only %luMB highmem pages available, ignoring highmem size of %uMB.\n", pages_to_mb(max_pfn - MAXMEM_PFN), pages_to_mb(highmem_pages));
- highmem_pages = 0;
+ printk("Warning reducing highmem=%uMB to: %luMB.\n",
+ pages_to_mb(highmem_pages),
+ pages_to_mb((max_pfn - MAXMEM_PFN)));
+ highmem_pages = max_pfn - MAXMEM_PFN;
}
max_low_pfn = MAXMEM_PFN;
#ifndef CONFIG_HIGHMEM
/* Maximum memory usable is what is directly addressable */
- printk(KERN_WARNING "Warning only %ldMB will be used.\n",
- MAXMEM>>20);
+ printk(KERN_WARNING "Warning only %luMB will be used.\n",
+ MAXMEM >> 20);
if (max_pfn > MAX_NONPAE_PFN)
printk(KERN_WARNING "Use a PAE enabled kernel.\n");
else
@@ -690,26 +700,63 @@ unsigned long __init find_max_low_pfn(vo
}
#endif /* !CONFIG_X86_PAE */
#endif /* !CONFIG_HIGHMEM */
- } else {
- if (highmem_pages == -1)
- highmem_pages = 0;
+ } else if (highmem_pages == -1)
+ highmem_pages = 0;
#ifdef CONFIG_HIGHMEM
- if (highmem_pages >= max_pfn) {
- printk(KERN_ERR "highmem size specified (%uMB) is bigger than pages available (%luMB)!.\n", pages_to_mb(highmem_pages), pages_to_mb(max_pfn));
- highmem_pages = 0;
- }
- if (highmem_pages) {
- if (max_low_pfn-highmem_pages < 64*1024*1024/PAGE_SIZE){
- printk(KERN_ERR "highmem size %uMB results in smaller than 64MB lowmem, ignoring it.\n", pages_to_mb(highmem_pages));
- highmem_pages = 0;
- }
- max_low_pfn -= highmem_pages;
- }
+ if (!highmem_pages)
+ goto out;
+ if (max_pfn < PAGES_FOR_64MB + ZONE_REQUIRED_PAGE_ALIGNMENT * 2) {
+ printk(KERN_ERR "Error highmem support requires at least %luMB "
+ "but only %luMB are available.\n",
+ pages_to_mb(PAGES_FOR_64MB +
+ ZONE_REQUIRED_PAGE_ALIGNMENT * 2),
+ pages_to_mb(max_pfn));
+ highmem_pages = 0;
+ goto out;
+ }
+ if (highmem_pages > max_pfn) {
+ printk(KERN_WARNING "Warning highmem=%uMB is bigger than "
+ "available %luMB and will be adjusted.\n",
+ pages_to_mb(highmem_pages), pages_to_mb(max_pfn));
+ }
+ if (highmem_pages <= ZONE_REQUIRED_PAGE_ALIGNMENT) {
+ printk(KERN_WARNING "Warning highmem=%uMB is too small and has "
+ "been adjusted to: %luMB.\n",
+ pages_to_mb(highmem_pages),
+ pages_to_mb(ZONE_REQUIRED_PAGE_ALIGNMENT * 2));
+ highmem_pages = ZONE_REQUIRED_PAGE_ALIGNMENT * 2;
+ }
+ if (max_low_pfn < highmem_pages ||
+ max_low_pfn-highmem_pages < PAGES_FOR_64MB){
+ highmem_pages = max_low_pfn - PAGES_FOR_64MB;
+ printk(KERN_WARNING "Warning highmem size adjusted for a "
+ "minimum of 64MB lowmem to: %uMB.\n",
+ pages_to_mb(highmem_pages));
+ }
+ max_low_pfn -= highmem_pages;
+
+ if (max_low_pfn & ZONE_REQUIRED_PAGE_ALIGNMENT_MASK) {
+ printk(KERN_WARNING "Warning bad highmem zone alignment 0x%lx, "
+ "highmem size will be adjusted.\n",
+ (max_low_pfn & ZONE_REQUIRED_PAGE_ALIGNMENT_MASK) <<
+ PAGE_SHIFT);
+ highmem_pages -= ZONE_REQUIRED_PAGE_ALIGNMENT -
+ (max_low_pfn & ZONE_REQUIRED_PAGE_ALIGNMENT_MASK);
+ max_low_pfn &= ~ZONE_REQUIRED_PAGE_ALIGNMENT_MASK;
+ max_low_pfn += ZONE_REQUIRED_PAGE_ALIGNMENT;
+ printk(KERN_WARNING "Warning lowmem size adjusted for zone "
+ "alignment to: %luMB.\n",
+ pages_to_mb(max_low_pfn));
+ printk(KERN_WARNING "Warning highmem size adjusted for zone "
+ "alignment to: %uMB.\n",
+ pages_to_mb(highmem_pages));
+ }
+out:
#else
- if (highmem_pages)
- printk(KERN_ERR "ignoring highmem size on non-highmem kernel!\n");
+ if (highmem_pages)
+ printk(KERN_ERR "ignoring highmem size on non-highmem "
+ "kernel!\n");
#endif
- }
return max_low_pfn;
}
diff -puN Documentation/kernel-parameters.txt~highmem-equals-user-friendliness Documentation/kernel-parameters.txt
--- 25/Documentation/kernel-parameters.txt~highmem-equals-user-friendliness 2004-02-09 00:14:08.000000000 -0800
+++ 25-akpm/Documentation/kernel-parameters.txt 2004-02-09 00:14:08.000000000 -0800
@@ -394,6 +394,14 @@ running once the system is up.
hd?= [HW] (E)IDE subsystem
hd?lun= See Documentation/ide.txt.
+ highmem=size[KMG] [IA32,KNL,BOOT] forces highmem to be at most 'size' bytes.
+ This works even on boxes with at least 72MB RAM that have no
+ highmem otherwise. This also works to reduce highmem size on
+ bigger boxes.
+
+ Note: highmem is adjusted downward for proper zone alignment
+ of the highmem physical start address
+
hisax= [HW,ISDN]
See Documentation/isdn/README.HiSax.
_