Commit ed2f2400 authored by Zhang Zhen's avatar Zhang Zhen Committed by Linus Torvalds
Browse files

memory-hotplug: add sysfs valid_zones attribute

Currently memory-hotplug has two limits:

1. If the memory block is in ZONE_NORMAL, you can change it to
   ZONE_MOVABLE, but this memory block must be adjacent to ZONE_MOVABLE.

2. If the memory block is in ZONE_MOVABLE, you can change it to
   ZONE_NORMAL, but this memory block must be adjacent to ZONE_NORMAL.

With this patch, we can easy to know a memory block can be onlined to
which zone, and don't need to know the above two limits.

Updated the related Documentation.

[ use conventional comment layout]
[ fix build with CONFIG_MEMORY_HOTREMOVE=n]
[ remove unused local zone_prev]
Signed-off-by: default avatarZhang Zhen <>
Cc: Dave Hansen <>
Cc: David Rientjes <>
Cc: Toshi Kani <>
Cc: Yasuaki Ishimatsu <>
Cc: Naoya Horiguchi <>
Cc: Wang Nan <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent cc71aba3
......@@ -61,6 +61,14 @@ Users: hotplug memory remove tools
What: /sys/devices/system/memory/memoryX/valid_zones
Date: July 2014
Contact: Zhang Zhen <>
The file /sys/devices/system/memory/memoryX/valid_zones is
read-only and is designed to show which zone this memory
block can be onlined to.
What: /sys/devices/system/memoryX/nodeY
Date: October 2009
Contact: Linux Memory Management list <>
......@@ -155,6 +155,7 @@ Under each memory block, you can see 4 files:
'phys_index' : read-only and contains memory block id, same as XXX.
'state' : read-write
......@@ -170,6 +171,15 @@ Under each memory block, you can see 4 files:
block is removable and a value of 0 indicates that
it is not removable. A memory block is removable only if
every section in the block is removable.
'valid_zones' : read-only: designed to show which zones this memory block
can be onlined to.
The first column shows it's default zone.
"memory6/valid_zones: Normal Movable" shows this memoryblock
can be onlined to ZONE_NORMAL by default and to ZONE_MOVABLE
by online_movable.
"memory7/valid_zones: Movable Normal" shows this memoryblock
can be onlined to ZONE_MOVABLE by default and to ZONE_NORMAL
by online_kernel.
These directories/files appear after physical memory hotplug phase.
......@@ -408,7 +418,6 @@ node if necessary.
- allowing memory hot-add to ZONE_MOVABLE. maybe we need some switch like
sysctl or new control file.
- showing memory block and physical device relationship.
- showing memory block is under ZONE_MOVABLE or not
- test and make it better memory offlining.
- support HugeTLB page migration and offlining.
- memmap removing at memory offline.
......@@ -373,6 +373,45 @@ static ssize_t show_phys_device(struct device *dev,
return sprintf(buf, "%d\n", mem->phys_device);
static ssize_t show_valid_zones(struct device *dev,
struct device_attribute *attr, char *buf)
struct memory_block *mem = to_memory_block(dev);
unsigned long start_pfn, end_pfn;
unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
struct page *first_page;
struct zone *zone;
start_pfn = section_nr_to_pfn(mem->start_section_nr);
end_pfn = start_pfn + nr_pages;
first_page = pfn_to_page(start_pfn);
/* The block contains more than one zone can not be offlined. */
if (!test_pages_in_a_zone(start_pfn, end_pfn))
return sprintf(buf, "none\n");
zone = page_zone(first_page);
if (zone_idx(zone) == ZONE_MOVABLE - 1) {
/*The mem block is the last memoryblock of this zone.*/
if (end_pfn == zone_end_pfn(zone))
return sprintf(buf, "%s %s\n",
zone->name, (zone + 1)->name);
if (zone_idx(zone) == ZONE_MOVABLE) {
/*The mem block is the first memoryblock of ZONE_MOVABLE.*/
if (start_pfn == zone->zone_start_pfn)
return sprintf(buf, "%s %s\n",
zone->name, (zone - 1)->name);
return sprintf(buf, "%s\n", zone->name);
static DEVICE_ATTR(valid_zones, 0444, show_valid_zones, NULL);
static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);
static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state);
static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL);
......@@ -523,6 +562,9 @@ static struct attribute *memory_memblk_attrs[] = {
......@@ -84,6 +84,7 @@ extern int zone_grow_waitqueues(struct zone *zone, unsigned long nr_pages);
extern int add_one_highpage(struct page *page, int pfn, int bad_ppro);
/* VM interface that may be used by firmware interface */
extern int online_pages(unsigned long, unsigned long, int);
extern int test_pages_in_a_zone(unsigned long, unsigned long);
extern void __offline_isolated_pages(unsigned long, unsigned long);
typedef void (*online_page_callback_t)(struct page *page);
......@@ -1307,7 +1307,7 @@ int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
* Confirm all pages in a range [start, end) is belongs to the same zone.
static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
unsigned long pfn;
struct zone *zone = NULL;
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