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Date: Thu, 26 Jun 2008 16:28:38 -0700
From: Badari Pulavarty <pbadari@...ibm.com>
To: akpm@...ux-foundation.org,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH] Add sysfs removable attribute for hotplug memory remove
Hi Andrew,
Recently realized that this patch came out of -mm tree and never
made it back in. I was supposed to update the description & comments
and add documentation for API.
Here is the updated version. Could you please include it in -mm ?
Thanks,
Badari
Memory may be hot-removed on a per-memory-block basis, particularly on POWER
where the SPARSEMEM section size often matches the memory-block size. A
user-level agent must be able to identify which sections of memory are likely
to be removable before attempting the potentially expensive operation. This
patch adds a file called "removable" to the memory directory in sysfs to
help such an agent. In this patch, a memory block is considered removable if;
o It contains only MOVABLE pageblocks
o It contains only pageblocks with free pages regardless of pageblock type
On the other hand, a memory block starting with a PageReserved() page will
never be considered removable. Without this patch, the user-agent is
forced to choose a memory block to remove randomly.
Sample output of the sysfs files:
./memory/memory0/removable: 0
./memory/memory1/removable: 0
./memory/memory2/removable: 0
./memory/memory3/removable: 0
./memory/memory4/removable: 0
./memory/memory5/removable: 0
./memory/memory6/removable: 0
./memory/memory7/removable: 1
./memory/memory8/removable: 0
./memory/memory9/removable: 0
./memory/memory10/removable: 0
./memory/memory11/removable: 0
./memory/memory12/removable: 0
./memory/memory13/removable: 0
./memory/memory14/removable: 0
./memory/memory15/removable: 0
./memory/memory16/removable: 0
./memory/memory17/removable: 1
./memory/memory18/removable: 1
./memory/memory19/removable: 1
./memory/memory20/removable: 1
./memory/memory21/removable: 1
./memory/memory22/removable: 1
Signed-off-by: Badari Pulavarty <pbadari@...ibm.com>
Signed-off-by: Mel Gorman <mel@....ul.ie>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---
Documentation/ABI/testing/sysfs-devices-memory | 24 ++++++++++
drivers/base/memory.c | 19 +++++++
include/linux/memory_hotplug.h | 12 +++++
mm/memory_hotplug.c | 60 +++++++++++++++++++++++++
4 files changed, 115 insertions(+)
Index: linux-2.6.26-rc7/drivers/base/memory.c
===================================================================
--- linux-2.6.26-rc7.orig/drivers/base/memory.c 2008-06-20 16:19:44.000000000 -0700
+++ linux-2.6.26-rc7/drivers/base/memory.c 2008-06-23 15:21:56.000000000 -0700
@@ -100,6 +100,21 @@ static ssize_t show_mem_phys_index(struc
}
/*
+ * Show whether the section of memory is likely to be hot-removable
+ */
+static ssize_t show_mem_removable(struct sys_device *dev, char *buf)
+{
+ unsigned long start_pfn;
+ int ret;
+ struct memory_block *mem =
+ container_of(dev, struct memory_block, sysdev);
+
+ start_pfn = section_nr_to_pfn(mem->phys_index);
+ ret = is_mem_section_removable(start_pfn, PAGES_PER_SECTION);
+ return sprintf(buf, "%d\n", ret);
+}
+
+/*
* online, offline, going offline, etc.
*/
static ssize_t show_mem_state(struct sys_device *dev, char *buf)
@@ -258,6 +273,7 @@ static ssize_t show_phys_device(struct s
static SYSDEV_ATTR(phys_index, 0444, show_mem_phys_index, NULL);
static SYSDEV_ATTR(state, 0644, show_mem_state, store_mem_state);
static SYSDEV_ATTR(phys_device, 0444, show_phys_device, NULL);
+static SYSDEV_ATTR(removable, 0444, show_mem_removable, NULL);
#define mem_create_simple_file(mem, attr_name) \
sysdev_create_file(&mem->sysdev, &attr_##attr_name)
@@ -346,6 +362,8 @@ static int add_memory_block(unsigned lon
ret = mem_create_simple_file(mem, state);
if (!ret)
ret = mem_create_simple_file(mem, phys_device);
+ if (!ret)
+ ret = mem_create_simple_file(mem, removable);
return ret;
}
@@ -390,6 +408,7 @@ int remove_memory_block(unsigned long no
mem_remove_simple_file(mem, phys_index);
mem_remove_simple_file(mem, state);
mem_remove_simple_file(mem, phys_device);
+ mem_remove_simple_file(mem, removable);
unregister_memory(mem, section);
return 0;
Index: linux-2.6.26-rc7/include/linux/memory_hotplug.h
===================================================================
--- linux-2.6.26-rc7.orig/include/linux/memory_hotplug.h 2008-06-20 16:19:44.000000000 -0700
+++ linux-2.6.26-rc7/include/linux/memory_hotplug.h 2008-06-23 15:21:56.000000000 -0700
@@ -199,6 +199,18 @@ extern int walk_memory_resource(unsigned
unsigned long nr_pages, void *arg,
int (*func)(unsigned long, unsigned long, void *));
+#ifdef CONFIG_MEMORY_HOTREMOVE
+
+extern int is_mem_section_removable(unsigned long pfn, unsigned long nr_pages);
+
+#else
+static inline int is_mem_section_removable(unsigned long pfn,
+ unsigned long nr_pages)
+{
+ return 0;
+}
+#endif /* CONFIG_MEMORY_HOTREMOVE */
+
extern int add_memory(int nid, u64 start, u64 size);
extern int arch_add_memory(int nid, u64 start, u64 size);
extern int remove_memory(u64 start, u64 size);
Index: linux-2.6.26-rc7/mm/memory_hotplug.c
===================================================================
--- linux-2.6.26-rc7.orig/mm/memory_hotplug.c 2008-06-20 16:19:44.000000000 -0700
+++ linux-2.6.26-rc7/mm/memory_hotplug.c 2008-06-23 15:21:56.000000000 -0700
@@ -521,6 +521,66 @@ EXPORT_SYMBOL_GPL(add_memory);
#ifdef CONFIG_MEMORY_HOTREMOVE
/*
+ * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
+ * set and the size of the free page is given by page_order(). Using this,
+ * the function determines if the pageblock contains only free pages.
+ * Due to buddy contraints, a free page at least the size of a pageblock will
+ * be located at the start of the pageblock
+ */
+static inline int pageblock_free(struct page *page)
+{
+ return PageBuddy(page) && page_order(page) >= pageblock_order;
+}
+
+/* Return the start of the next active pageblock after a given page */
+static struct page *next_active_pageblock(struct page *page)
+{
+ int pageblocks_stride;
+
+ /* Ensure the starting page is pageblock-aligned */
+ BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1));
+
+ /* Move forward by at least 1 * pageblock_nr_pages */
+ pageblocks_stride = 1;
+
+ /* If the entire pageblock is free, move to the end of free page */
+ if (pageblock_free(page))
+ pageblocks_stride += page_order(page) - pageblock_order;
+
+ return page + (pageblocks_stride * pageblock_nr_pages);
+}
+
+/* Checks if this range of memory is likely to be hot-removable. */
+int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
+{
+ int type;
+ struct page *page = pfn_to_page(start_pfn);
+ struct page *end_page = page + nr_pages;
+
+ /* Check the starting page of each pageblock within the range */
+ for (; page < end_page; page = next_active_pageblock(page)) {
+ type = get_pageblock_migratetype(page);
+
+ /*
+ * A pageblock containing MOVABLE or free pages is considered
+ * removable
+ */
+ if (type != MIGRATE_MOVABLE && !pageblock_free(page))
+ return 0;
+
+ /*
+ * A pageblock starting with a PageReserved page is not
+ * considered removable.
+ */
+ if (PageReserved(page))
+ return 0;
+ }
+
+ /* All pageblocks in the memory block are likely to be hot-removable */
+ return 1;
+}
+
+/*
* 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)
Index: linux-2.6.26-rc7/Documentation/ABI/testing/sysfs-devices-memory
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.26-rc7/Documentation/ABI/testing/sysfs-devices-memory 2008-06-26 15:37:06.000000000 -0700
@@ -0,0 +1,24 @@
+What: /sys/devices/system/memory
+Date: June 2008
+Contact: Badari Pulavarty <pbadari@...ibm.com>
+Description:
+ The /sys/devices/system/memory contains a snapshot of the
+ internal state of the kernel memory blocks. Files could be
+ added or removed dynamically to represent hot-add/remove
+ operations.
+
+Users: hotplug memory add/remove tools
+ https://w3.opensource.ibm.com/projects/powerpc-utils/
+
+What: /sys/devices/system/memory/memoryX/removable
+Date: June 2008
+Contact: Badari Pulavarty <pbadari@...ibm.com>
+Description:
+ The file /sys/devices/system/memory/memoryX/removable
+ indicates whether this memory block is removable or not.
+ This is useful for a user-level agent to determine
+ identify removable sections of the memory before attempting
+ potentially expensive hot-remove memory operation
+
+Users: hotplug memory remove tools
+ https://w3.opensource.ibm.com/projects/powerpc-utils/
--
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