[PATCH] memory-hotplug: add sysfs zone_index attribute

Zhang Zhen
2014-07-24T07:42:12Z

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.

Without this patch, we don't know which zone a memory block is in.
So we don't know which memory block is adjacent to ZONE_MOVABLE or
ZONE_NORMAL.

On the other hand, with this patch, we can easy to know newly added
memory is added as ZONE_NORMAL (for powerpc, ZONE_DMA, for x86_32,
ZONE_HIGHMEM).

Updated the related Documentation.

Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
---
Documentation/ABI/testing/sysfs-devices-memory | 9 +++++++++
Documentation/memory-hotplug.txt | 4 +++-
drivers/base/memory.c | 15 ++++++++++++++-
3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-devices-memory b/Documentation/ABI/testing/sysfs-devices-memory
index 7405de2..39d3423 100644
--- a/Documentation/ABI/testing/sysfs-devices-memory
+++ b/Documentation/ABI/testing/sysfs-devices-memory
@@ -61,6 +61,15 @@ Users: hotplug memory remove tools
http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils

+What: /sys/devices/system/memory/memoryX/zone_index
+Date: July 2014
+Contact: Zhang Zhen <zhenzhang.zhang@huawei.com>
+Description:
+ The file /sys/devices/system/memory/memoryX/zone_index
+ is read-only and is designed to show which zone this memory block is in.
+Users: hotplug memory remove tools
+ http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils
+
What: /sys/devices/system/memoryX/nodeY
Date: October 2009
Contact: Linux Memory Management list <linux-mm@kvack.org>
diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
index 45134dc..07019133 100644
--- a/Documentation/memory-hotplug.txt
+++ b/Documentation/memory-hotplug.txt
@@ -155,6 +155,7 @@ Under each memory block, you can see 4 files:
/sys/devices/system/memory/memoryXXX/phys_device
/sys/devices/system/memory/memoryXXX/state
/sys/devices/system/memory/memoryXXX/removable
+/sys/devices/system/memory/memoryXXX/zone_index

'phys_index' : read-only and contains memory block id, same as XXX.
'state' : read-write
@@ -170,6 +171,8 @@ 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.
+'zone_index' : read-only: designed to show which zone this memory block
+ is in.

NOTE:
These directories/files appear after physical memory hotplug phase.
@@ -408,7 +411,6 @@ 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.
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 89f752d..3434d97 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -373,11 +373,23 @@ static ssize_t show_phys_device(struct device *dev,
return sprintf(buf, "%d\n", mem->phys_device);
}

+static ssize_t show_mem_zone_index(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct memory_block *mem = to_memory_block(dev);
+ struct page *first_page;
+ struct zone *zone;
+
+ first_page = pfn_to_page(mem->start_section_nr << PFN_SECTION_SHIFT);
+ zone = page_zone(first_page);
+ return sprintf(buf, "%s\n", zone->name);
+}
+
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);
static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL);
-
+static DEVICE_ATTR(zone_index, 0444, show_mem_zone_index, NULL);
/*
* Block size attribute stuff
*/
@@ -521,6 +533,7 @@ static struct attribute *memory_memblk_attrs[] = {
&dev_attr_state.attr,
&dev_attr_phys_device.attr,
&dev_attr_removable.attr,
+ &dev_attr_zone_index.attr,
NULL
};

--
1.8.1.2

.