[PATCH] 2.4.25-rc1: Add user friendliness to highmem= option

[PATCH] 2.4.25-rc1: Add user friendliness to highmem= option

[Michael Frank]

Marcelo,

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

Highmem emulation can be used on any machine with at least 68MB RAM.

The patch does not add to bloat as it part of __init code.

Please consider applying it as it makes this option quite usable

Regards
Michael

Examples on a machine with 495MB available RAM:

highmem=1m

Warning highmem=1MB is too small and has been adjusted to: 4MB.
Warning bad highmem zone alignment 0x1f0000, highmem size will be adjusted.
Warning lowmem size adjusted  for zone alignment to: 492MB.
Warning highmem size adjusted for zone alignment to: 3MB.
3MB HIGHMEM available.
492MB LOWMEM available.

highmem=300m

Warning bad highmem zone alignment 0x1f0000, highmem size will be adjusted.
Warning lowmem size adjusted  for zone alignment to: 196MB.
Warning highmem size adjusted for zone alignment to: 299MB.
299MB HIGHMEM available.
196MB LOWMEM available.

highmem=450m

Warning highmem size adjusted for a minimum of 64MB lowmem to: 431MB.
431MB HIGHMEM available.
64MB LOWMEM available.

highmem=5000m

Warning highmem=5000MB is bigger than available 495MB and will be adjusted.
Warning highmem size adjusted for a minimum of 64MB lowmem to: 431MB.
431MB HIGHMEM available.
64MB LOWMEM available.

mem=70m highmem=300m

user-defined physical RAM map:
 user: 0000000000000000 - 000000000009fc00 (usable)
 user: 000000000009fc00 - 00000000000a0000 (reserved)
 user: 00000000000f0000 - 0000000000100000 (reserved)
 user: 0000000000100000 - 0000000004600000 (usable)
Warning highmem=300MB is bigger than available 70MB and will be adjusted.
Warning highmem size adjusted for a minimum of 64MB lowmem to: 6MB.
6MB HIGHMEM available.
64MB LOWMEM available.

mem=66m highmem=1m

user-defined physical RAM map:
 user: 0000000000000000 - 000000000009fc00 (usable)
 user: 000000000009fc00 - 00000000000a0000 (reserved)
 user: 00000000000f0000 - 0000000000100000 (reserved)
 user: 0000000000100000 - 0000000004200000 (usable)
Error highmem support requires at least 68MB but only 66MB are available.
0MB HIGHMEM available.
66MB LOWMEM available.

mem=68m highmem=10m

user-defined physical RAM map:
 user: 0000000000000000 - 000000000009fc00 (usable)
 user: 000000000009fc00 - 00000000000a0000 (reserved)
 user: 00000000000f0000 - 0000000000100000 (reserved)
 user: 0000000000100000 - 0000000004400000 (usable)
Warning highmem size adjusted for a minimum of 64MB lowmem to: 4MB.
4MB HIGHMEM available.
64MB LOWMEM available.

diff -uN -r -X /home/mhf/sys/dont/dontdiff linux-2.4.25-rc1-Vanilla/arch/i386/kernel/setup.c linux-2.4.25-rc1-mhf176/arch/i386/kernel/setup.c
--- linux-2.4.25-rc1-Vanilla/arch/i386/kernel/setup.c	2004-02-07 02:52:37.000000000 +0800
+++ linux-2.4.25-rc1-mhf176/arch/i386/kernel/setup.c	2004-02-07 18:53:47.000000000 +0800
@@ -861,9 +861,12 @@
                         disable_ioapic_setup();
 #endif
 		/*
-		 * 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.
 		 */
 		else if (!memcmp(from, "highmem=", 8))
 			highmem_pages = memparse(from+8, &from) >> PAGE_SHIFT;
@@ -918,25 +921,31 @@
 /*
  * 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)
+
 static unsigned long __init find_max_low_pfn(void)
 {
 	unsigned long max_low_pfn;
 
 	max_low_pfn = max_pfn;
+
 	if (max_low_pfn > MAXMEM_PFN) {
 		if (highmem_pages == -1)
 			highmem_pages = max_pfn - MAXMEM_PFN;
 		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=%luMB 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 %ldMB will be used.\n",MAXMEM>>20);
 		if (max_pfn > MAX_NONPAE_PFN)
 			printk(KERN_WARNING "Use a PAE enabled kernel.\n");
 		else
@@ -950,27 +959,53 @@
 		}
 #endif /* !CONFIG_X86_PAE */
 #endif /* !CONFIG_HIGHMEM */
-	} else {
-		if (highmem_pages == -1)
-			highmem_pages = 0;
+	} else if (highmem_pages == -1)
+		highmem_pages = 0;
 #if 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 %uMB but only %uMB 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: %uMB.\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("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: %uMB.\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));
+	}
 #else
-		if (highmem_pages)
-			printk(KERN_ERR "ignoring highmem size on non-highmem kernel!\n");
+	if (highmem_pages)
+		printk(KERN_ERR "Error highmem size on non-highmem kernel ignored\n");
 #endif
-	}
-
+out:
 	return max_low_pfn;
 }
 
diff -uN -r -X /home/mhf/sys/dont/dontdiff linux-2.4.25-rc1-Vanilla/Documentation/kernel-parameters.txt linux-2.4.25-rc1-mhf176/Documentation/kernel-parameters.txt
--- linux-2.4.25-rc1-Vanilla/Documentation/kernel-parameters.txt	2004-02-06 17:06:14.000000000 +0800
+++ linux-2.4.25-rc1-mhf176/Documentation/kernel-parameters.txt	2004-02-07 19:10:39.000000000 +0800
@@ -241,6 +241,12 @@
 
 	hfmodem=	[HW,AX25]
 
+	highmem=size[KMG]	[IA32,KNL,BOOT] forces highmem to be at most 'size' bytes.
+	This works even on boxes with at least 68MB 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]
 
 	i810=		[HW,DRM]

Re: [PATCH] 2.4.25-rc1: Add user friendliness to highmem= option

[Rik van Riel]

On Sat, 7 Feb 2004, Michael Frank wrote:

> 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

This is awesome!  Thanks.

Marcelo, could you please apply this ? ;)

-- 
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan

Re: [PATCH] 2.4.25-rc1: Add user friendliness to highmem= option

[Michael Frank]

On Saturday 07 February 2004 23:08, Rik van Riel wrote:
> On Sat, 7 Feb 2004, Michael Frank wrote:
> 
> > 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
> 
> This is awesome!  Thanks.
> 
> Marcelo, could you please apply this ? ;)
> 

Thank you very much for your encouraging response ;)

What is your opinion on shutting down the kernel on
zone alignment errors (applies to all arches) and
the force_bug method it uses to do so?

Regards
Michael

> -- 
> "Debugging is twice as hard as writing the code in the first place.
> Therefore, if you write the code as cleverly as possible, you are,
> by definition, not smart enough to debug it." - Brian W. Kernighan
> 
> 
> 

Re: [PATCH] 2.4.25-rc1: Add user friendliness to highmem= option

[Rik van Riel]

On Sat, 7 Feb 2004, Michael Frank wrote:

> Thank you very much for your encouraging response ;)
> 
> What is your opinion on shutting down the kernel on
> zone alignment errors (applies to all arches) and
> the force_bug method it uses to do so?

I think the init code should be smart enough to avoid the
zone alignment errors in the first place.

Still, we should have a fallback in page_alloc.c to check
the arch init code, otherwise problems related to zone
alignment become nearly impossible to debug.

-- 
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan