mm: fix-up zone present pages

PATCH In review wujianguo 2 participants 3 messages Aug 20, 2012 – Aug 24, 2012

Subsystems (4)

Memory management MM core Page allocator Memory hot(un)plug

lore

Share & tools

lore

wujianguo

author

2012-08-20 06:38 UTC #0 lore raw

PATCH 1/1 mm: fix-up zone present pages

From: Jianguo Wu <[email protected]>

Hi all,

	I think zone->present_pages indicates pages that buddy system can management,
it should be:
	zone->present_pages = spanned pages - absent pages - bootmem pages,
but now:
	zone->present_pages = spanned pages - absent pages - memmap pages.

spanned pagesï¼štotal size, including holes.
absent pages: holes.
bootmem pages: pages used in system boot, managed by bootmem allocator. memmap pages: pages used by page structs.

This may cause zone->present_pages less than it should be.
For example, numa node 1 has ZONE_NORMAL and ZONE_MOVABLE,
it's memmap and other bootmem will be allocated from ZONE_MOVABLE,
so ZONE_NORMAL's present_pages should be spanned pages - absent pages,
but now it also minus memmap pages(free_area_init_core), which are actually allocated from ZONE_MOVABLE. When offline all memory of a zone, This will cause zone->present_pages less than 0, because present_pages is unsigned long type, it is actually
a very large integer, it indirectly caused zone->watermark[WMARK_MIN] become a large integer(setup_per_zone_wmarks()), than cause totalreserve_pages become a large integer(calculate_totalreserve_pages()), and finally cause memory allocating failure when fork process(__vm_enough_memory()).

[root@localhost ~]# dmesg
-bash: fork: Cannot allocate memory

I think bug described in http://marc.info/?l=linux-mm&m4502182714186&w=2 is also caused by wrong zone present pages.

This patch intends to fix-up zone->present_pages when memory are freed to buddy system in x86_64 and IA64 platform.

Thanks.

Signed-off-by Jianguo Wu <[email protected]>

Signed-off-by Jiang Liu <[email protected]>

---
 arch/ia64/mm/init.c |    1 +
 include/linux/mm.h  |    4 ++++
 mm/bootmem.c        |    9 ++++++++-
 mm/memory_hotplug.c |    7 +++++++
 mm/nobootmem.c      |    3 +++
 mm/page_alloc.c     |   34 ++++++++++++++++++++++++++++++++++
 6 files changed, 57 insertions(+), 1 deletions(-)

arch/ia64/mm/init.c +1 -0

index b960ba0..c78e3fd 100644
@@ -640,6 +640,7 @@ mem_init (void)
 	free_floating_node_bootmem();
 #endif
 
+	reset_zone_present_pages();
 	for_each_online_pgdat(pgdat)
 		if (pgdat->bdata->node_bootmem_map)
 			totalram_pages += free_all_bootmem_node(pgdat);

include/linux/mm.h +4 -0

index 311be90..a1bd8ea 100644
@@ -1662,5 +1662,9 @@ static inline unsigned int debug_guardpage_minorder(void) { return 0; }
 static inline bool page_is_guard(struct page *page) { return false; }
 #endif /* CONFIG_DEBUG_PAGEALLOC */
 
+extern void reset_zone_present_pages(void);
+extern void fixup_zone_present_pages(int nid, unsigned long start_pfn,
+				unsigned long end_pfn);
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */

mm/bootmem.c +8 -1

index bcb63ac..e00b491 100644
@@ -198,6 +198,8 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 			int order = ilog2(BITS_PER_LONG);
 
 			__free_pages_bootmem(pfn_to_page(start), order);
+			fixup_zone_present_pages(page_to_nid(pfn_to_page(start)),
+					start, start + BITS_PER_LONG);
 			count += BITS_PER_LONG;
 			start += BITS_PER_LONG;
 		} else {

@@ -208,6 +210,8 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 				if (vec & 1) {
 					page = pfn_to_page(start + off);
 					__free_pages_bootmem(page, 0);
+					fixup_zone_present_pages(page_to_nid(page),
+							start + off, start + off + 1);
 					count++;
 				}
 				vec >>= 1;

@@ -221,8 +225,11 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 	pages = bdata->node_low_pfn - bdata->node_min_pfn;
 	pages = bootmem_bootmap_pages(pages);
 	count += pages;
-	while (pages--)
+	while (pages--) {
+		fixup_zone_present_pages(page_to_nid(page),
+				page_to_pfn(page), page_to_pfn(page) + 1);
 		__free_pages_bootmem(page++, 0);
+	}
 
 	bdebug("nid=%td released=%lx\n", bdata - bootmem_node_data, count);

mm/memory_hotplug.c +7 -0

index 3ad25f9..bc7e7a2 100644
@@ -106,6 +106,7 @@ static void get_page_bootmem(unsigned long info,  struct page *page,
 void __ref put_page_bootmem(struct page *page)
 {
 	unsigned long type;
+	struct zone *zone;
 
 	type = (unsigned long) page->lru.next;
 	BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||

@@ -116,6 +117,12 @@ void __ref put_page_bootmem(struct page *page)
 		set_page_private(page, 0);
 		INIT_LIST_HEAD(&page->lru);
 		__free_pages_bootmem(page, 0);
+
+		zone = page_zone(page);
+		zone_span_writelock(zone);
+		zone->present_pages++;
+		zone_span_writeunlock(zone);
+		totalram_pages++;
 	}
 
 }

mm/nobootmem.c +3 -0

index 4055730..8027861 100644
@@ -116,6 +116,8 @@ static unsigned long __init __free_memory_core(phys_addr_t start,
 		return 0;
 
 	__free_pages_memory(start_pfn, end_pfn);
+	fixup_zone_present_pages(pfn_to_nid(start >> PAGE_SHIFT),
+			start_pfn, end_pfn);
 
 	return end_pfn - start_pfn;
 }

@@ -126,6 +128,7 @@ unsigned long __init free_low_memory_core_early(int nodeid)
 	phys_addr_t start, end, size;
 	u64 i;
 
+	reset_zone_present_pages();
 	for_each_free_mem_range(i, MAX_NUMNODES, &start, &end, NULL)
 		count += __free_memory_core(start, end);

mm/page_alloc.c +34 -0

index fcb0932..36c35bb 100644
@@ -6074,3 +6074,37 @@ void dump_page(struct page *page)
 	dump_page_flags(page->flags);
 	mem_cgroup_print_bad_page(page);
 }
+
+/* reset zone->present_pages */
+void reset_zone_present_pages(void)
+{
+	struct zone *z;
+	int i, nid;
+
+	for_each_node_state(nid, N_HIGH_MEMORY) {
+		for (i = 0; i < MAX_NR_ZONES; i++) {
+			z = NODE_DATA(nid)->node_zones + i;
+			z->present_pages = 0;
+		}
+	}
+}
+
+/* calculate zone's present pages in buddy system */
+void fixup_zone_present_pages(int nid, unsigned long start_pfn,
+				unsigned long end_pfn)
+{
+	struct zone *z;
+	unsigned long zone_start_pfn, zone_end_pfn;
+	int i;
+
+	for (i = 0; i < MAX_NR_ZONES; i++) {
+		z = NODE_DATA(nid)->node_zones + i;
+		zone_start_pfn = z->zone_start_pfn;
+		zone_end_pfn = zone_start_pfn + z->spanned_pages;
+
+		/* if the two regions intersect */
+		if (!(zone_start_pfn >= end_pfn	|| zone_end_pfn <= start_pfn))
+			z->present_pages += min(end_pfn, zone_end_pfn) -
+								max(start_pfn, zone_start_pfn);
+	}
+}

Signature · 5 lines

1.7.6.1



.

Petr Tesarik

2012-08-21 03:55 UTC #1 lore raw

Dne Po 20. srpna 2012 08:38:10 wujianguo napsal(a):

Quoted 8 lines

From: Jianguo Wu <[email protected]>

Hi all,

	I think zone->present_pages indicates pages that buddy system can
management, it should be:
	zone->present_pages = spanned pages - absent pages - bootmem pages,
but now:
	zone->present_pages = spanned pages - absent pages - memmap pages.

Quoted 4 lines

spanned pagesï¼štotal size, including holes.
absent pages: holes.
bootmem pages: pages used in system boot, managed by bootmem allocator. memmap pages: pages used by page structs.

Absolutely. The memory allocated to page structs should be counted in.

Quoted 13 lines

This may cause zone->present_pages less than it should be.
For example, numa node 1 has ZONE_NORMAL and ZONE_MOVABLE,
it's memmap and other bootmem will be allocated from ZONE_MOVABLE, so ZONE_NORMAL's present_pages should be spanned pages - absent pages, but now it also minus memmap pages(free_area_init_core), which are actually allocated from ZONE_MOVABLE. When offline all memory of a zone, This will cause zone->present_pages less than 0, because present_pages is unsigned long type, it is actually a very large integer, it indirectly caused zone->watermark[WMARK_MIN] become a large integer(setup_per_zone_wmarks()), than cause totalreserve_pages become a large integer(calculate_totalreserve_pages()), and finally cause memory allocating failure when fork process(__vm_enough_memory()).

Quoted 5 lines

[root@localhost ~]# dmesg
-bash: fork: Cannot allocate memory
I think bug described in http://marc.info/?l=linux-mm&m4502182714186&w=2
is also caused by wrong zone present pages.

And yes, I can confirm that the bug I reported is caused by a too low number for the present pages counter. Your patch does fix the bug for me.

Thanks!
Petr Tesarik

wujianguo

author

2012-08-24 02:31 UTC #2 lore raw

Quoted 14 lines · Petr Tesarik

Dne Po 20. srpna 2012 08:38:10 wujianguo napsal(a):
Quoted 8 lines
From: Jianguo Wu <[email protected]>
Hi all,
	I think zone->present_pages indicates pages that buddy system can
management, it should be:
	zone->present_pages = spanned pages - absent pages - bootmem pages,
but now:
	zone->present_pages = spanned pages - absent pages - memmap pages.
Quoted 4 lines
spanned pagesï¼štotal size, including holes.
absent pages: holes.
bootmem pages: pages used in system boot, managed by bootmem allocator. memmap pages: pages used by page structs.

Quoted 2 lines

Absolutely. The memory allocated to page structs should be counted in.

Hi Petr,
Bootmem pages include the memory allocated to page structs.

Thanks!
Jianguo Wu

Quoted 25 lines

Quoted 13 lines
This may cause zone->present_pages less than it should be.
For example, numa node 1 has ZONE_NORMAL and ZONE_MOVABLE,
it's memmap and other bootmem will be allocated from ZONE_MOVABLE, so ZONE_NORMAL's present_pages should be spanned pages - absent pages, but now it also minus memmap pages(free_area_init_core), which are actually allocated from ZONE_MOVABLE. When offline all memory of a zone, This will cause zone->present_pages less than 0, because present_pages is unsigned long type, it is actually a very large integer, it indirectly caused zone->watermark[WMARK_MIN] become a large integer(setup_per_zone_wmarks()), than cause totalreserve_pages become a large integer(calculate_totalreserve_pages()), and finally cause memory allocating failure when fork process(__vm_enough_memory()).
Quoted 5 lines
[root@localhost ~]# dmesg
-bash: fork: Cannot allocate memory
I think bug described in http://marc.info/?l=linux-mm&m4502182714186&w=2
is also caused by wrong zone present pages.
And yes, I can confirm that the bug I reported is caused by a too low number for the present pages counter. Your patch does fix the bug for me.
Thanks!
Petr Tesarik