x86_64: Make sparsemem/vmemmap the default memory model

x86_64: Make sparsemem/vmemmap the default memory model

[Christoph Lameter]

Use sparsemem as the only memory model for UP, SMP and NUMA.

Measurements indicate that DISCONTIGMEM has a higher
overhead than sparsemem. And FLATMEMs benefits are minimal. So I think its
best to simply standardize on sparsemem.

Results of page allocator tests (test can be had via git from the slab git
tree on git.kernel.org. See the branch tests)

Measurements in cycle counts. 1000 allocations were performed and then the
average cycle count was calculated.

Order	FlatMem	Discontig	SparseMem
0	  639	  665		  641
1	  567	  647		  593
2	  679	  774		  692
3	  763	  967		  781
4	  961	 1501		  962
5	 1356	 2344		 1392
6	 2224	 3982		 2336
7	 4869	 7225		 5074
8	12500	14048		12732
9	27926	28223		28165
10	58578	58714		58682

If this patch is accepted then we can remove the code for discontig and
flatmem support from x86_64.

(Not sure if I got all the config settings right. Andy?)

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 arch/x86/Kconfig.x86_64 |   13 +------------
 1 file changed, 1 insertion(+), 12 deletions(-)

Index: linux-2.6/arch/x86/Kconfig.x86_64
===================================================================
--- linux-2.6.orig/arch/x86/Kconfig.x86_64	2007-11-12 15:17:50.721767735 -0800
+++ linux-2.6/arch/x86/Kconfig.x86_64	2007-11-12 15:21:16.659017509 -0800
@@ -390,28 +390,17 @@ config NUMA_EMU
 	  into virtual nodes when booted with "numa=fake=N", where N is the
 	  number of nodes. This is only useful for debugging.
 
-config ARCH_DISCONTIGMEM_ENABLE
-       bool
-       depends on NUMA
-       default y
-
-config ARCH_DISCONTIGMEM_DEFAULT
+config ARCH_SPARSEMEM_DEFAULT
 	def_bool y
-	depends on NUMA
 
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
-	depends on (NUMA || EXPERIMENTAL)
 	select SPARSEMEM_VMEMMAP_ENABLE
 
 config ARCH_MEMORY_PROBE
 	def_bool y
 	depends on MEMORY_HOTPLUG
 
-config ARCH_FLATMEM_ENABLE
-	def_bool y
-	depends on !NUMA
-
 source "mm/Kconfig"
 
 config MEMORY_HOTPLUG_RESERVE

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Re: x86_64: Make sparsemem/vmemmap the default memory model

[Andi Kleen]

On Tuesday 13 November 2007 00:52:14 Christoph Lameter wrote:
> Use sparsemem as the only memory model for UP, SMP and NUMA.
> 
> Measurements indicate that DISCONTIGMEM has a higher
> overhead than sparsemem. And FLATMEMs benefits are minimal. So I think its
> best to simply standardize on sparsemem.

How about the memory overhead? Is it the same too?
And code size vs flatmem?

-Andi

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Re: x86_64: Make sparsemem/vmemmap the default memory model

[Christoph Lameter]

On Tue, 13 Nov 2007, Andi Kleen wrote:

> On Tuesday 13 November 2007 00:52:14 Christoph Lameter wrote:
> > Use sparsemem as the only memory model for UP, SMP and NUMA.
> > 
> > Measurements indicate that DISCONTIGMEM has a higher
> > overhead than sparsemem. And FLATMEMs benefits are minimal. So I think its
> > best to simply standardize on sparsemem.
> 
> How about the memory overhead? Is it the same too?
> And code size vs flatmem?

SMP Sparsemem
-------------

Kernel size:

   text    data     bss     dec     hex filename
3849268  397739 1264856 5511863  541ab7 vmlinux

             total       used       free     shared    buffers     cached
Mem:       8242252      41164    8201088          0        352      11512
-/+ buffers/cache:      29300    8212952
Swap:      9775512          0    9775512

SMP Flatmem
-----------

Kernel size:

   text    data     bss     dec     hex filename
3844612  397739 1264536 5506887  540747 vmlinux

So 4.5k growth in text size vs. FLATMEM.

             total       used       free     shared    buffers     cached
Mem:       8244052      40544    8203508          0        352      11484
-/+ buffers/cache:      28708    8215344

2k growth in overall memory use after boot.



NUMA discontig:

   text    data     bss     dec     hex filename
3888124  470659 1276504 5635287  55fcd7 vmlinux

             total       used       free     shared    buffers     cached
Mem:       8256256      56908    8199348          0        352      11496
-/+ buffers/cache:      45060    8211196
Swap:      9775512          0    9775512

NUMA sparse:

   text    data     bss     dec     hex filename
3896428  470659 1276824 5643911  561e87 vmlinux


8k text growth. Given that we fully inline virt_to_page and friends now 
that is rather good.

             total       used       free     shared    buffers     cached
Mem:       8264720      57240    8207480          0        352      11516
-/+ buffers/cache:      45372    8219348
Swap:      9775512          0    9775512

Hmmm... More memory free? How did that happen? More pages cached for some 
reason. The total available memory is increased by 8k.

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Re: x86_64: Make sparsemem/vmemmap the default memory model

[Andi Kleen]

> Hmmm... More memory free? How did that happen? More pages cached for some
> reason. The total available memory is increased by 8k.

Nice. Looks all reasonable. Thanks for the numbers.

-Andi

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Re: x86_64: Make sparsemem/vmemmap the default memory model

[Christoph Lameter]

On Tue, 13 Nov 2007, Andi Kleen wrote:

> 
> > Hmmm... More memory free? How did that happen? More pages cached for some
> > reason. The total available memory is increased by 8k.
> 
> Nice. Looks all reasonable. Thanks for the numbers.


Ok here is the patch to remove DISCONTIG and FLATMEM




x86_64: Make sparsemem/vmemmap the default memory model

Use sparsemem as the only memory model for UP, SMP and NUMA.
Measurements indicate that DISCONTIGMEM has a higher overhead
than sparsemem. And FLATMEMs benefits are minimal. So I think its
best to simply standardize on sparsemem.

Results of page allocator tests (test can be had via git from slab git
tree branch tests)

Measurements in cycle counts. 1000 allocations were performed and then the
average cycle count was calculated.

Order	FlatMem	Discontig	SparseMem
0	  639	  665		  641
1	  567	  647		  593
2	  679	  774		  692
3	  763	  967		  781
4	  961	 1501		  962
5	 1356	 2344		 1392
6	 2224	 3982		 2336
7	 4869	 7225		 5074
8	12500	14048		12732
9	27926	28223		28165
10	58578	58714		58682

Memory use:

SMP Sparsemem
-------------

Kernel size:

   text    data     bss     dec     hex filename
3849268  397739 1264856 5511863  541ab7 vmlinux

             total       used       free     shared    buffers     cached
Mem:       8242252      41164    8201088          0        352      11512
-/+ buffers/cache:      29300    8212952
Swap:      9775512          0    9775512

SMP Flatmem
-----------

Kernel size:

   text    data     bss     dec     hex filename
3844612  397739 1264536 5506887  540747 vmlinux

So 4.5k growth in text size vs. FLATMEM.

             total       used       free     shared    buffers     cached
Mem:       8244052      40544    8203508          0        352      11484
-/+ buffers/cache:      28708    8215344

2k growth in overall memory use after boot.



NUMA discontig:

   text    data     bss     dec     hex filename
3888124  470659 1276504 5635287  55fcd7 vmlinux

             total       used       free     shared    buffers     cached
Mem:       8256256      56908    8199348          0        352      11496
-/+ buffers/cache:      45060    8211196
Swap:      9775512          0    9775512

NUMA sparse:

   text    data     bss     dec     hex filename
3896428  470659 1276824 5643911  561e87 vmlinux


8k text growth. Given that we fully inline virt_to_page and friends now
that is rather good.

             total       used       free     shared    buffers     cached
Mem:       8264720      57240    8207480          0        352      11516
-/+ buffers/cache:      45372    8219348
Swap:      9775512          0    9775512

The total available memory is increased by 8k.


This patch makes sparsemem the default and removes discontig and
flatmem support from x86.

Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 arch/x86/Kconfig.x86_64            |   21 -------------
 arch/x86/configs/x86_64_defconfig  |    9 -----
 arch/x86/kernel/machine_kexec_64.c |    5 ---
 arch/x86/mm/init_64.c              |   30 -------------------
 arch/x86/mm/ioremap_64.c           |   17 -----------
 arch/x86/mm/numa_64.c              |   21 -------------
 arch/x86/mm/srat_64.c              |   57 -------------------------------------
 include/asm-x86/mmzone_64.h        |    6 ---
 include/asm-x86/page_64.h          |    3 -
 9 files changed, 1 insertion(+), 168 deletions(-)

Index: linux-2.6/arch/x86/Kconfig.x86_64
===================================================================
--- linux-2.6.orig/arch/x86/Kconfig.x86_64	2007-11-12 19:10:56.697664127 -0800
+++ linux-2.6/arch/x86/Kconfig.x86_64	2007-11-12 19:14:02.437902563 -0800
@@ -411,42 +411,23 @@ config NUMA_EMU
 	  into virtual nodes when booted with "numa=fake=N", where N is the
 	  number of nodes. This is only useful for debugging.
 
-config ARCH_DISCONTIGMEM_ENABLE
-       bool
-       depends on NUMA
-       default y
-
-config ARCH_DISCONTIGMEM_DEFAULT
+config ARCH_SPARSEMEM_DEFAULT
 	def_bool y
-	depends on NUMA
 
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
-	depends on (NUMA || EXPERIMENTAL)
 	select SPARSEMEM_VMEMMAP_ENABLE
 
 config ARCH_MEMORY_PROBE
 	def_bool y
 	depends on MEMORY_HOTPLUG
 
-config ARCH_FLATMEM_ENABLE
-	def_bool y
-	depends on !NUMA
-
 source "mm/Kconfig"
 
-config MEMORY_HOTPLUG_RESERVE
-	def_bool y
-	depends on (MEMORY_HOTPLUG && DISCONTIGMEM)
-
 config HAVE_ARCH_EARLY_PFN_TO_NID
 	def_bool y
 	depends on NUMA
 
-config OUT_OF_LINE_PFN_TO_PAGE
-	def_bool y
-	depends on DISCONTIGMEM
-
 config NR_CPUS
 	int "Maximum number of CPUs (2-255)"
 	range 2 255
Index: linux-2.6/arch/x86/configs/x86_64_defconfig
===================================================================
--- linux-2.6.orig/arch/x86/configs/x86_64_defconfig	2007-11-12 18:27:12.516523443 -0800
+++ linux-2.6/arch/x86/configs/x86_64_defconfig	2007-11-12 19:14:02.441902438 -0800
@@ -145,15 +145,6 @@ CONFIG_K8_NUMA=y
 CONFIG_NODES_SHIFT=6
 CONFIG_X86_64_ACPI_NUMA=y
 CONFIG_NUMA_EMU=y
-CONFIG_ARCH_DISCONTIGMEM_ENABLE=y
-CONFIG_ARCH_DISCONTIGMEM_DEFAULT=y
-CONFIG_ARCH_SPARSEMEM_ENABLE=y
-CONFIG_SELECT_MEMORY_MODEL=y
-# CONFIG_FLATMEM_MANUAL is not set
-CONFIG_DISCONTIGMEM_MANUAL=y
-# CONFIG_SPARSEMEM_MANUAL is not set
-CONFIG_DISCONTIGMEM=y
-CONFIG_FLAT_NODE_MEM_MAP=y
 CONFIG_NEED_MULTIPLE_NODES=y
 # CONFIG_SPARSEMEM_STATIC is not set
 CONFIG_SPLIT_PTLOCK_CPUS=4
Index: linux-2.6/arch/x86/kernel/machine_kexec_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/machine_kexec_64.c	2007-11-12 18:27:12.524523631 -0800
+++ linux-2.6/arch/x86/kernel/machine_kexec_64.c	2007-11-12 19:14:02.453902454 -0800
@@ -234,10 +234,5 @@ NORET_TYPE void machine_kexec(struct kim
 void arch_crash_save_vmcoreinfo(void)
 {
 	VMCOREINFO_SYMBOL(init_level4_pgt);
-
-#ifdef CONFIG_ARCH_DISCONTIGMEM_ENABLE
-	VMCOREINFO_SYMBOL(node_data);
-	VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
-#endif
 }
 
Index: linux-2.6/arch/x86/mm/ioremap_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/ioremap_64.c	2007-11-12 18:27:12.552523359 -0800
+++ linux-2.6/arch/x86/mm/ioremap_64.c	2007-11-12 19:14:02.461902441 -0800
@@ -86,23 +86,6 @@ void __iomem * __ioremap(unsigned long p
 	if (phys_addr >= ISA_START_ADDRESS && last_addr < ISA_END_ADDRESS)
 		return (__force void __iomem *)phys_to_virt(phys_addr);
 
-#ifdef CONFIG_FLATMEM
-	/*
-	 * Don't allow anybody to remap normal RAM that we're using..
-	 */
-	if (last_addr < virt_to_phys(high_memory)) {
-		char *t_addr, *t_end;
- 		struct page *page;
-
-		t_addr = __va(phys_addr);
-		t_end = t_addr + (size - 1);
-	   
-		for(page = virt_to_page(t_addr); page <= virt_to_page(t_end); page++)
-			if(!PageReserved(page))
-				return NULL;
-	}
-#endif
-
 	pgprot = __pgprot(_PAGE_PRESENT | _PAGE_RW | _PAGE_GLOBAL
 			  | _PAGE_DIRTY | _PAGE_ACCESSED | flags);
 	/*
Index: linux-2.6/arch/x86/mm/numa_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/numa_64.c	2007-11-12 18:27:12.528523345 -0800
+++ linux-2.6/arch/x86/mm/numa_64.c	2007-11-12 19:24:34.601056905 -0800
@@ -149,12 +149,10 @@ int __init compute_hash_shift(struct boo
 	return shift;
 }
 
-#ifdef CONFIG_SPARSEMEM
 int early_pfn_to_nid(unsigned long pfn)
 {
 	return phys_to_nid(pfn << PAGE_SHIFT);
 }
-#endif
 
 static void * __init
 early_node_mem(int nodeid, unsigned long start, unsigned long end,
@@ -626,23 +624,4 @@ EXPORT_SYMBOL(node_to_cpumask);
 EXPORT_SYMBOL(memnode);
 EXPORT_SYMBOL(node_data);
 
-#ifdef CONFIG_DISCONTIGMEM
-/*
- * Functions to convert PFNs from/to per node page addresses.
- * These are out of line because they are quite big.
- * They could be all tuned by pre caching more state.
- * Should do that.
- */
 
-int pfn_valid(unsigned long pfn)
-{
-	unsigned nid;
-	if (pfn >= num_physpages)
-		return 0;
-	nid = pfn_to_nid(pfn);
-	if (nid == 0xff)
-		return 0;
-	return pfn >= node_start_pfn(nid) && (pfn) < node_end_pfn(nid);
-}
-EXPORT_SYMBOL(pfn_valid);
-#endif
Index: linux-2.6/include/asm-x86/mmzone_64.h
===================================================================
--- linux-2.6.orig/include/asm-x86/mmzone_64.h	2007-11-12 18:27:12.560523466 -0800
+++ linux-2.6/include/asm-x86/mmzone_64.h	2007-11-12 19:14:02.485902361 -0800
@@ -41,12 +41,6 @@ static inline __attribute__((pure)) int 
 #define node_end_pfn(nid)       (NODE_DATA(nid)->node_start_pfn + \
 				 NODE_DATA(nid)->node_spanned_pages)
 
-#ifdef CONFIG_DISCONTIGMEM
-#define pfn_to_nid(pfn) phys_to_nid((unsigned long)(pfn) << PAGE_SHIFT)
-
-extern int pfn_valid(unsigned long pfn);
-#endif
-
 #ifdef CONFIG_NUMA_EMU
 #define FAKE_NODE_MIN_SIZE	(64*1024*1024)
 #define FAKE_NODE_MIN_HASH_MASK	(~(FAKE_NODE_MIN_SIZE - 1uL))
Index: linux-2.6/include/asm-x86/page_64.h
===================================================================
--- linux-2.6.orig/include/asm-x86/page_64.h	2007-11-12 18:27:12.568523834 -0800
+++ linux-2.6/include/asm-x86/page_64.h	2007-11-12 19:14:02.497902025 -0800
@@ -121,9 +121,6 @@ extern unsigned long __phys_addr(unsigne
 #define __va(x)			((void *)((unsigned long)(x)+PAGE_OFFSET))
 #define __boot_va(x)		__va(x)
 #define __boot_pa(x)		__pa(x)
-#ifdef CONFIG_FLATMEM
-#define pfn_valid(pfn)		((pfn) < end_pfn)
-#endif
 
 #define virt_to_page(kaddr)	pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
 #define virt_addr_valid(kaddr)	pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
Index: linux-2.6/arch/x86/mm/init_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/init_64.c	2007-11-12 19:24:08.016577199 -0800
+++ linux-2.6/arch/x86/mm/init_64.c	2007-11-12 19:29:48.689827052 -0800
@@ -485,34 +485,6 @@ EXPORT_SYMBOL_GPL(memory_add_physaddr_to
 
 #endif /* CONFIG_MEMORY_HOTPLUG */
 
-#ifdef CONFIG_MEMORY_HOTPLUG_RESERVE
-/*
- * Memory Hotadd without sparsemem. The mem_maps have been allocated in advance,
- * just online the pages.
- */
-int __add_pages(struct zone *z, unsigned long start_pfn, unsigned long nr_pages)
-{
-	int err = -EIO;
-	unsigned long pfn;
-	unsigned long total = 0, mem = 0;
-	for (pfn = start_pfn; pfn < start_pfn + nr_pages; pfn++) {
-		if (pfn_valid(pfn)) {
-			online_page(pfn_to_page(pfn));
-			err = 0;
-			mem++;
-		}
-		total++;
-	}
-	if (!err) {
-		z->spanned_pages += total;
-		z->present_pages += mem;
-		z->zone_pgdat->node_spanned_pages += total;
-		z->zone_pgdat->node_present_pages += mem;
-	}
-	return err;
-}
-#endif
-
 static struct kcore_list kcore_mem, kcore_vmalloc, kcore_kernel, kcore_modules,
 			 kcore_vsyscall;
 
@@ -738,7 +710,6 @@ const char *arch_vma_name(struct vm_area
 	return NULL;
 }
 
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
 /*
  * Initialise the sparsemem vmemmap using huge-pages at the PMD level.
  */
@@ -781,7 +752,6 @@ int __meminit vmemmap_populate(struct pa
 
 	return 0;
 }
-#endif
 
 #ifdef CONFIG_NUMA
 int __meminit cpu_area_populate(void *start, unsigned long size,
Index: linux-2.6/arch/x86/mm/srat_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/srat_64.c	2007-11-12 19:24:54.344327144 -0800
+++ linux-2.6/arch/x86/mm/srat_64.c	2007-11-12 19:25:36.108577445 -0800
@@ -151,62 +151,6 @@ acpi_numa_processor_affinity_init(struct
 	       pxm, pa->apic_id, node);
 }
 
-#ifdef CONFIG_MEMORY_HOTPLUG_RESERVE
-/*
- * Protect against too large hotadd areas that would fill up memory.
- */
-static int hotadd_enough_memory(struct bootnode *nd)
-{
-	static unsigned long allocated;
-	static unsigned long last_area_end;
-	unsigned long pages = (nd->end - nd->start) >> PAGE_SHIFT;
-	long mem = pages * sizeof(struct page);
-	unsigned long addr;
-	unsigned long allowed;
-	unsigned long oldpages = pages;
-
-	if (mem < 0)
-		return 0;
-	allowed = (end_pfn - absent_pages_in_range(0, end_pfn)) * PAGE_SIZE;
-	allowed = (allowed / 100) * hotadd_percent;
-	if (allocated + mem > allowed) {
-		unsigned long range;
-		/* Give them at least part of their hotadd memory upto hotadd_percent
-		   It would be better to spread the limit out
-		   over multiple hotplug areas, but that is too complicated
-		   right now */
-		if (allocated >= allowed)
-			return 0;
-		range = allowed - allocated;
-		pages = (range / PAGE_SIZE);
-		mem = pages * sizeof(struct page);
-		nd->end = nd->start + range;
-	}
-	/* Not completely fool proof, but a good sanity check */
-	addr = find_e820_area(last_area_end, end_pfn<<PAGE_SHIFT, mem);
-	if (addr == -1UL)
-		return 0;
-	if (pages != oldpages)
-		printk(KERN_NOTICE "SRAT: Hotadd area limited to %lu bytes\n",
-			pages << PAGE_SHIFT);
-	last_area_end = addr + mem;
-	allocated += mem;
-	return 1;
-}
-
-static int update_end_of_memory(unsigned long end)
-{
-	found_add_area = 1;
-	if ((end >> PAGE_SHIFT) > end_pfn)
-		end_pfn = end >> PAGE_SHIFT;
-	return 1;
-}
-
-static inline int save_add_info(void)
-{
-	return hotadd_percent > 0;
-}
-#else
 int update_end_of_memory(unsigned long end) {return -1;}
 static int hotadd_enough_memory(struct bootnode *nd) {return 1;}
 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
@@ -214,7 +158,6 @@ static inline int save_add_info(void) {r
 #else
 static inline int save_add_info(void) {return 0;}
 #endif
-#endif
 /*
  * Update nodes_add and decide if to include add are in the zone.
  * Both SPARSE and RESERVE need nodes_add infomation.

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Re: x86_64: Make sparsemem/vmemmap the default memory model

[Ray Lee]

On Nov 12, 2007 7:42 PM, Christoph Lameter <clameter@sgi.com> wrote:
> Ok here is the patch to remove DISCONTIG and FLATMEM
>
> x86_64: Make sparsemem/vmemmap the default memory model
>
> Use sparsemem as the only memory model for UP, SMP and NUMA.
> Measurements indicate that DISCONTIGMEM has a higher overhead
> than sparsemem. And FLATMEMs benefits are minimal. So I think its
> best to simply standardize on sparsemem.
>
> Results of page allocator tests (test can be had via git from slab git
> tree branch tests)
>
> Measurements in cycle counts. 1000 allocations were performed and then the
> average cycle count was calculated.
>
> Order   FlatMem Discontig       SparseMem
> 0         639     665             641
> 1         567     647             593
> 2         679     774             692
> 3         763     967             781
> 4         961    1501             962
> 5        1356    2344            1392
> 6        2224    3982            2336
> 7        4869    7225            5074
> 8       12500   14048           12732
> 9       27926   28223           28165
> 10      58578   58714           58682

Discontig obviously needs to die. However, FlatMem is consistently
faster, averaging about 2.1% better overall for your numbers above. Is
the page allocator not, erm, a fast path, where that matters?

Order	Flat	Sparse	% diff
0	639	641	0.3
1	567	593	4.4
2	679	692	1.9
3	763	781	2.3
4	961	962	0.1
5	1356	1392	2.6
6	2224	2336	4.8
7	4869	5074	4.0
8	12500	12732	1.8
9	27926	28165	0.8
10	58578	58682	0.2

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Re: x86_64: Make sparsemem/vmemmap the default memory model

[Christoph Lameter]

On Mon, 12 Nov 2007, Ray Lee wrote:

> Discontig obviously needs to die. However, FlatMem is consistently
> faster, averaging about 2.1% better overall for your numbers above. Is
> the page allocator not, erm, a fast path, where that matters?
> 
> Order	Flat	Sparse	% diff
> 0	639	641	0.3

IMHO Order 0 currently matters most and the difference is negligible 
there.

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Re: x86_64: Make sparsemem/vmemmap the default memory model

[Jörn Engel]

On Mon, 12 November 2007 20:41:10 -0800, Christoph Lameter wrote:
> On Mon, 12 Nov 2007, Ray Lee wrote:
> 
> > Discontig obviously needs to die. However, FlatMem is consistently
> > faster, averaging about 2.1% better overall for your numbers above. Is
> > the page allocator not, erm, a fast path, where that matters?
> > 
> > Order	Flat	Sparse	% diff
> > 0	639	641	0.3
> 
> IMHO Order 0 currently matters most and the difference is negligible 
> there.

Is it?  I am a bit concerned about the non-monotonic distribution.
Difference starts a near-0, grows to 4.4, drops to near-0, grows to 4.9,
drops to near-0.

Order   Flat    Sparse  % diff
0       639     641     0.3
1       567     593     4.4
2       679     692     1.9
3       763     781     2.3
4       961     962     0.1
5       1356    1392    2.6
6       2224    2336    4.8
7       4869    5074    4.0
8       12500   12732   1.8
9       27926   28165   0.8
10      58578   58682   0.2

Is there an explanation for this behaviour?  More to the point, could
repeated runs also return 4% difference for order-0?

JA?rn

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Re: x86_64: Make sparsemem/vmemmap the default memory model

[Christoph Lameter]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 1480 bytes --]

On Tue, 13 Nov 2007, Jörn Engel wrote:

> On Mon, 12 November 2007 20:41:10 -0800, Christoph Lameter wrote:
> > On Mon, 12 Nov 2007, Ray Lee wrote:
> > 
> > > Discontig obviously needs to die. However, FlatMem is consistently
> > > faster, averaging about 2.1% better overall for your numbers above. Is
> > > the page allocator not, erm, a fast path, where that matters?
> > > 
> > > Order	Flat	Sparse	% diff
> > > 0	639	641	0.3
> > 
> > IMHO Order 0 currently matters most and the difference is negligible 
> > there.
> 
> Is it?  I am a bit concerned about the non-monotonic distribution.
> Difference starts a near-0, grows to 4.4, drops to near-0, grows to 4.9,
> drops to near-0.

The problem also is that the comparison here is between a SMP config for 
flatmem vs a NUMA config for sparsemem. There is additional overhead in 
the NUMA config. 

The effect may also be due to the system being able to place 
some pages in the same 2MB section as the memmap with flatmem. However, 
that is only feasable immeidately after bootup. In regular operations this 
should vanish.

Could you run your own test to verify?

> Is there an explanation for this behaviour?  More to the point, could
> repeated runs also return 4% difference for order-0?

I hope I have given some above. The number of the page allocator suggests 
that we have far too much fat in the allocation paths. IMHO reasonable 
numbers for an order-0 alloc should be ~100 cycles.

Re: x86_64: Make sparsemem/vmemmap the default memory model

[Jörn Engel]

On Tue, 13 November 2007 13:52:17 -0800, Christoph Lameter wrote:
> 
> Could you run your own test to verify?

You bastard!  You know I'm too lazy to do that. ;)

As long as the order-0 number is stable across multiple runs I don't
mind.  The numbers just looked suspiciously as if they were not stable.
That's all.

JA?rn

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They do it because life wouldn't have any meaning for them if they didn't.
That's why I draw cartoons.  It's my life.
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Re: x86_64: Make sparsemem/vmemmap the default memory model

[Andrew Morton]

On Mon, 12 Nov 2007 19:42:31 -0800 (PST)
Christoph Lameter <clameter@sgi.com> wrote:

> x86_64: Make sparsemem/vmemmap the default memory model
> 
> Use sparsemem as the only memory model for UP, SMP and NUMA.
> Measurements indicate that DISCONTIGMEM has a higher overhead
> than sparsemem. And FLATMEMs benefits are minimal. So I think its
> best to simply standardize on sparsemem.

Unfortunately some loon has gone and merged the i386 and x86_64 Kconfig
files.  I was fixing that up but I worry what effects these Kconfig changes
might have on, for example, i386 NUMA setups.

So I'll duck this version, sorry.

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Re: x86_64: Make sparsemem/vmemmap the default memory model

[Christoph Lameter]

On Thu, 15 Nov 2007, Andrew Morton wrote:

> Unfortunately some loon has gone and merged the i386 and x86_64 Kconfig
> files.  I was fixing that up but I worry what effects these Kconfig changes
> might have on, for example, i386 NUMA setups.
> 
> So I'll duck this version, sorry.

Is there a tree that I can rediff the patch against?

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Re: x86_64: Make sparsemem/vmemmap the default memory model

[Andrew Morton]

On Thu, 15 Nov 2007 18:24:54 -0800 (PST) Christoph Lameter <clameter@sgi.com> wrote:

> On Thu, 15 Nov 2007, Andrew Morton wrote:
> 
> > Unfortunately some loon has gone and merged the i386 and x86_64 Kconfig
> > files.  I was fixing that up but I worry what effects these Kconfig changes
> > might have on, for example, i386 NUMA setups.
> > 
> > So I'll duck this version, sorry.
> 
> Is there a tree that I can rediff the patch against?

Mainline.

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x86_64: Make sparsemem/vmemmap the default memory model V2

[Christoph Lameter]

Updated version against mainline. Looks even a bit cleaner.



x86_64: Make sparsemem/vmemmap the default memory model V2

V1->V2:
- Rediff against new upstream x86 code that unifies the Kconfig files.

Use sparsemem as the only memory model for UP, SMP and NUMA.
Measurements indicate that DISCONTIGMEM has a higher overhead
than sparsemem. And FLATMEMs benefits are minimal. So I think its
best to simply standardize on sparsemem.

Results of page allocator tests (test can be had via git from slab git
tree branch tests)

Measurements in cycle counts. 1000 allocations were performed and then the
average cycle count was calculated.

Order	FlatMem	Discontig	SparseMem
0	  639	  665		  641
1	  567	  647		  593
2	  679	  774		  692
3	  763	  967		  781
4	  961	 1501		  962
5	 1356	 2344		 1392
6	 2224	 3982		 2336
7	 4869	 7225		 5074
8	12500	14048		12732
9	27926	28223		28165
10	58578	58714		58682

(Note that FlatMem is an SMP config and the rest NUMA configurations)

Memory use:

SMP Sparsemem
-------------

Kernel size:

   text    data     bss     dec     hex filename
3849268  397739 1264856 5511863  541ab7 vmlinux

             total       used       free     shared    buffers     cached
Mem:       8242252      41164    8201088          0        352      11512
-/+ buffers/cache:      29300    8212952
Swap:      9775512          0    9775512

SMP Flatmem
-----------

Kernel size:

   text    data     bss     dec     hex filename
3844612  397739 1264536 5506887  540747 vmlinux

So 4.5k growth in text size vs. FLATMEM.

             total       used       free     shared    buffers     cached
Mem:       8244052      40544    8203508          0        352      11484
-/+ buffers/cache:      28708    8215344

2k growth in overall memory use after boot.



NUMA discontig:

   text    data     bss     dec     hex filename
3888124  470659 1276504 5635287  55fcd7 vmlinux

             total       used       free     shared    buffers     cached
Mem:       8256256      56908    8199348          0        352      11496
-/+ buffers/cache:      45060    8211196
Swap:      9775512          0    9775512

NUMA sparse:

   text    data     bss     dec     hex filename
3896428  470659 1276824 5643911  561e87 vmlinux


8k text growth. Given that we fully inline virt_to_page and friends now
that is rather good.

             total       used       free     shared    buffers     cached
Mem:       8264720      57240    8207480          0        352      11516
-/+ buffers/cache:      45372    8219348
Swap:      9775512          0    9775512

The total available memory is increased by 8k.


This patch makes sparsemem the default and removes discontig and
flatmem support from x86.

Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 arch/x86/Kconfig                   |   20 +++++-------
 arch/x86/configs/x86_64_defconfig  |    9 -----
 arch/x86/kernel/machine_kexec_64.c |    5 ---
 arch/x86/mm/init_64.c              |   30 -------------------
 arch/x86/mm/ioremap_64.c           |   17 -----------
 arch/x86/mm/numa_64.c              |   21 -------------
 arch/x86/mm/srat_64.c              |   57 -------------------------------------
 include/asm-x86/mmzone_64.h        |    6 ---
 include/asm-x86/page_64.h          |    3 -
 include/asm-x86/sparsemem_64.h     |    4 --
 10 files changed, 8 insertions(+), 164 deletions(-)

Index: linux-2.6/arch/x86/configs/x86_64_defconfig
===================================================================
--- linux-2.6.orig/arch/x86/configs/x86_64_defconfig	2007-11-13 11:52:34.785633363 -0800
+++ linux-2.6/arch/x86/configs/x86_64_defconfig	2007-11-15 19:39:59.073745644 -0800
@@ -145,15 +145,6 @@ CONFIG_K8_NUMA=y
 CONFIG_NODES_SHIFT=6
 CONFIG_X86_64_ACPI_NUMA=y
 CONFIG_NUMA_EMU=y
-CONFIG_ARCH_DISCONTIGMEM_ENABLE=y
-CONFIG_ARCH_DISCONTIGMEM_DEFAULT=y
-CONFIG_ARCH_SPARSEMEM_ENABLE=y
-CONFIG_SELECT_MEMORY_MODEL=y
-# CONFIG_FLATMEM_MANUAL is not set
-CONFIG_DISCONTIGMEM_MANUAL=y
-# CONFIG_SPARSEMEM_MANUAL is not set
-CONFIG_DISCONTIGMEM=y
-CONFIG_FLAT_NODE_MEM_MAP=y
 CONFIG_NEED_MULTIPLE_NODES=y
 # CONFIG_SPARSEMEM_STATIC is not set
 CONFIG_SPLIT_PTLOCK_CPUS=4
Index: linux-2.6/arch/x86/kernel/machine_kexec_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/machine_kexec_64.c	2007-11-13 11:52:34.793633597 -0800
+++ linux-2.6/arch/x86/kernel/machine_kexec_64.c	2007-11-15 19:39:59.126128308 -0800
@@ -234,10 +234,5 @@ NORET_TYPE void machine_kexec(struct kim
 void arch_crash_save_vmcoreinfo(void)
 {
 	VMCOREINFO_SYMBOL(init_level4_pgt);
-
-#ifdef CONFIG_ARCH_DISCONTIGMEM_ENABLE
-	VMCOREINFO_SYMBOL(node_data);
-	VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
-#endif
 }
 
Index: linux-2.6/arch/x86/mm/ioremap_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/ioremap_64.c	2007-11-13 11:52:34.801633088 -0800
+++ linux-2.6/arch/x86/mm/ioremap_64.c	2007-11-15 19:39:59.149995698 -0800
@@ -86,23 +86,6 @@ void __iomem * __ioremap(unsigned long p
 	if (phys_addr >= ISA_START_ADDRESS && last_addr < ISA_END_ADDRESS)
 		return (__force void __iomem *)phys_to_virt(phys_addr);
 
-#ifdef CONFIG_FLATMEM
-	/*
-	 * Don't allow anybody to remap normal RAM that we're using..
-	 */
-	if (last_addr < virt_to_phys(high_memory)) {
-		char *t_addr, *t_end;
- 		struct page *page;
-
-		t_addr = __va(phys_addr);
-		t_end = t_addr + (size - 1);
-	   
-		for(page = virt_to_page(t_addr); page <= virt_to_page(t_end); page++)
-			if(!PageReserved(page))
-				return NULL;
-	}
-#endif
-
 	pgprot = __pgprot(_PAGE_PRESENT | _PAGE_RW | _PAGE_GLOBAL
 			  | _PAGE_DIRTY | _PAGE_ACCESSED | flags);
 	/*
Index: linux-2.6/arch/x86/mm/numa_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/numa_64.c	2007-11-13 11:52:34.805632772 -0800
+++ linux-2.6/arch/x86/mm/numa_64.c	2007-11-15 19:39:59.157245106 -0800
@@ -149,12 +149,10 @@ int __init compute_hash_shift(struct boo
 	return shift;
 }
 
-#ifdef CONFIG_SPARSEMEM
 int early_pfn_to_nid(unsigned long pfn)
 {
 	return phys_to_nid(pfn << PAGE_SHIFT);
 }
-#endif
 
 static void * __init
 early_node_mem(int nodeid, unsigned long start, unsigned long end,
@@ -626,23 +624,4 @@ EXPORT_SYMBOL(node_to_cpumask);
 EXPORT_SYMBOL(memnode);
 EXPORT_SYMBOL(node_data);
 
-#ifdef CONFIG_DISCONTIGMEM
-/*
- * Functions to convert PFNs from/to per node page addresses.
- * These are out of line because they are quite big.
- * They could be all tuned by pre caching more state.
- * Should do that.
- */
 
-int pfn_valid(unsigned long pfn)
-{
-	unsigned nid;
-	if (pfn >= num_physpages)
-		return 0;
-	nid = pfn_to_nid(pfn);
-	if (nid == 0xff)
-		return 0;
-	return pfn >= node_start_pfn(nid) && (pfn) < node_end_pfn(nid);
-}
-EXPORT_SYMBOL(pfn_valid);
-#endif
Index: linux-2.6/include/asm-x86/mmzone_64.h
===================================================================
--- linux-2.6.orig/include/asm-x86/mmzone_64.h	2007-11-13 11:52:34.825632852 -0800
+++ linux-2.6/include/asm-x86/mmzone_64.h	2007-11-15 19:39:59.173245524 -0800
@@ -41,12 +41,6 @@ static inline __attribute__((pure)) int 
 #define node_end_pfn(nid)       (NODE_DATA(nid)->node_start_pfn + \
 				 NODE_DATA(nid)->node_spanned_pages)
 
-#ifdef CONFIG_DISCONTIGMEM
-#define pfn_to_nid(pfn) phys_to_nid((unsigned long)(pfn) << PAGE_SHIFT)
-
-extern int pfn_valid(unsigned long pfn);
-#endif
-
 #ifdef CONFIG_NUMA_EMU
 #define FAKE_NODE_MIN_SIZE	(64*1024*1024)
 #define FAKE_NODE_MIN_HASH_MASK	(~(FAKE_NODE_MIN_SIZE - 1uL))
Index: linux-2.6/include/asm-x86/page_64.h
===================================================================
--- linux-2.6.orig/include/asm-x86/page_64.h	2007-11-13 11:52:34.833632806 -0800
+++ linux-2.6/include/asm-x86/page_64.h	2007-11-15 19:39:59.216745079 -0800
@@ -121,9 +121,6 @@ extern unsigned long __phys_addr(unsigne
 #define __va(x)			((void *)((unsigned long)(x)+PAGE_OFFSET))
 #define __boot_va(x)		__va(x)
 #define __boot_pa(x)		__pa(x)
-#ifdef CONFIG_FLATMEM
-#define pfn_valid(pfn)		((pfn) < end_pfn)
-#endif
 
 #define virt_to_page(kaddr)	pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
 #define virt_addr_valid(kaddr)	pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
Index: linux-2.6/arch/x86/mm/init_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/init_64.c	2007-11-15 12:19:14.820392365 -0800
+++ linux-2.6/arch/x86/mm/init_64.c	2007-11-15 19:39:59.228495304 -0800
@@ -484,34 +484,6 @@ EXPORT_SYMBOL_GPL(memory_add_physaddr_to
 
 #endif /* CONFIG_MEMORY_HOTPLUG */
 
-#ifdef CONFIG_MEMORY_HOTPLUG_RESERVE
-/*
- * Memory Hotadd without sparsemem. The mem_maps have been allocated in advance,
- * just online the pages.
- */
-int __add_pages(struct zone *z, unsigned long start_pfn, unsigned long nr_pages)
-{
-	int err = -EIO;
-	unsigned long pfn;
-	unsigned long total = 0, mem = 0;
-	for (pfn = start_pfn; pfn < start_pfn + nr_pages; pfn++) {
-		if (pfn_valid(pfn)) {
-			online_page(pfn_to_page(pfn));
-			err = 0;
-			mem++;
-		}
-		total++;
-	}
-	if (!err) {
-		z->spanned_pages += total;
-		z->present_pages += mem;
-		z->zone_pgdat->node_spanned_pages += total;
-		z->zone_pgdat->node_present_pages += mem;
-	}
-	return err;
-}
-#endif
-
 static struct kcore_list kcore_mem, kcore_vmalloc, kcore_kernel, kcore_modules,
 			 kcore_vsyscall;
 
@@ -737,7 +709,6 @@ const char *arch_vma_name(struct vm_area
 	return NULL;
 }
 
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
 /*
  * Initialise the sparsemem vmemmap using huge-pages at the PMD level.
  */
@@ -780,4 +751,3 @@ int __meminit vmemmap_populate(struct pa
 
 	return 0;
 }
-#endif
Index: linux-2.6/arch/x86/mm/srat_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/srat_64.c	2007-11-13 11:52:34.821633366 -0800
+++ linux-2.6/arch/x86/mm/srat_64.c	2007-11-15 19:39:59.228495304 -0800
@@ -151,62 +151,6 @@ acpi_numa_processor_affinity_init(struct
 	       pxm, pa->apic_id, node);
 }
 
-#ifdef CONFIG_MEMORY_HOTPLUG_RESERVE
-/*
- * Protect against too large hotadd areas that would fill up memory.
- */
-static int hotadd_enough_memory(struct bootnode *nd)
-{
-	static unsigned long allocated;
-	static unsigned long last_area_end;
-	unsigned long pages = (nd->end - nd->start) >> PAGE_SHIFT;
-	long mem = pages * sizeof(struct page);
-	unsigned long addr;
-	unsigned long allowed;
-	unsigned long oldpages = pages;
-
-	if (mem < 0)
-		return 0;
-	allowed = (end_pfn - absent_pages_in_range(0, end_pfn)) * PAGE_SIZE;
-	allowed = (allowed / 100) * hotadd_percent;
-	if (allocated + mem > allowed) {
-		unsigned long range;
-		/* Give them at least part of their hotadd memory upto hotadd_percent
-		   It would be better to spread the limit out
-		   over multiple hotplug areas, but that is too complicated
-		   right now */
-		if (allocated >= allowed)
-			return 0;
-		range = allowed - allocated;
-		pages = (range / PAGE_SIZE);
-		mem = pages * sizeof(struct page);
-		nd->end = nd->start + range;
-	}
-	/* Not completely fool proof, but a good sanity check */
-	addr = find_e820_area(last_area_end, end_pfn<<PAGE_SHIFT, mem);
-	if (addr == -1UL)
-		return 0;
-	if (pages != oldpages)
-		printk(KERN_NOTICE "SRAT: Hotadd area limited to %lu bytes\n",
-			pages << PAGE_SHIFT);
-	last_area_end = addr + mem;
-	allocated += mem;
-	return 1;
-}
-
-static int update_end_of_memory(unsigned long end)
-{
-	found_add_area = 1;
-	if ((end >> PAGE_SHIFT) > end_pfn)
-		end_pfn = end >> PAGE_SHIFT;
-	return 1;
-}
-
-static inline int save_add_info(void)
-{
-	return hotadd_percent > 0;
-}
-#else
 int update_end_of_memory(unsigned long end) {return -1;}
 static int hotadd_enough_memory(struct bootnode *nd) {return 1;}
 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
@@ -214,7 +158,6 @@ static inline int save_add_info(void) {r
 #else
 static inline int save_add_info(void) {return 0;}
 #endif
-#endif
 /*
  * Update nodes_add and decide if to include add are in the zone.
  * Both SPARSE and RESERVE need nodes_add infomation.
Index: linux-2.6/arch/x86/Kconfig
===================================================================
--- linux-2.6.orig/arch/x86/Kconfig	2007-11-15 12:19:41.950157617 -0800
+++ linux-2.6/arch/x86/Kconfig	2007-11-15 19:39:59.240495606 -0800
@@ -889,19 +889,23 @@ config HAVE_ARCH_ALLOC_REMAP
 
 config ARCH_FLATMEM_ENABLE
 	def_bool y
-	depends on (X86_32 && ARCH_SELECT_MEMORY_MODEL && X86_PC) || (X86_64 && !NUMA)
+	depends on X86_32 && ARCH_SELECT_MEMORY_MODEL && X86_PC
 
 config ARCH_DISCONTIGMEM_ENABLE
 	def_bool y
-	depends on NUMA
+	depends on NUMA && X86_32
 
 config ARCH_DISCONTIGMEM_DEFAULT
 	def_bool y
-	depends on NUMA
+	depends on NUMA && X86_32
+
+config ARCH_SPARSEMEM_DEFAULT
+	def_bool y
+	depends on X86_64
 
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
-	depends on NUMA || (EXPERIMENTAL && (X86_PC || X86_64))
+	depends on X86_64 || NUMA || (EXPERIMENTAL && X86_PC)
 	select SPARSEMEM_STATIC if X86_32
 	select SPARSEMEM_VMEMMAP_ENABLE if X86_64
 
@@ -1205,18 +1209,10 @@ config ARCH_ENABLE_MEMORY_HOTPLUG
 	def_bool y
 	depends on X86_64 || (X86_32 && HIGHMEM)
 
-config MEMORY_HOTPLUG_RESERVE
-	def_bool X86_64
-	depends on (MEMORY_HOTPLUG && DISCONTIGMEM)
-
 config HAVE_ARCH_EARLY_PFN_TO_NID
 	def_bool X86_64
 	depends on NUMA
 
-config OUT_OF_LINE_PFN_TO_PAGE
-	def_bool X86_64
-	depends on DISCONTIGMEM
-
 menu "Power management options"
 	depends on !X86_VOYAGER
 
Index: linux-2.6/include/asm-x86/sparsemem_64.h
===================================================================
--- linux-2.6.orig/include/asm-x86/sparsemem_64.h	2007-11-15 19:50:25.169427205 -0800
+++ linux-2.6/include/asm-x86/sparsemem_64.h	2007-11-15 19:50:32.165046504 -0800
@@ -1,8 +1,6 @@
 #ifndef _ASM_X86_64_SPARSEMEM_H
 #define _ASM_X86_64_SPARSEMEM_H 1
 
-#ifdef CONFIG_SPARSEMEM
-
 /*
  * generic non-linear memory support:
  *
@@ -21,6 +19,4 @@
 
 extern int early_pfn_to_nid(unsigned long pfn);
 
-#endif /* CONFIG_SPARSEMEM */
-
 #endif /* _ASM_X86_64_SPARSEMEM_H */

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