memory-hotplug: add sysfs removable attribute for hotplug memory remove
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@us.ibm.com> Signed-off-by: Mel Gorman <mel@csn.ul.ie> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Badari Pulavarty
Linus Torvalds
Родитель
2f7f24eca3
Коммит
5c755e9fd8
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@ -0,0 +1,24 @@
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What: /sys/devices/system/memory
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Date: June 2008
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Contact: Badari Pulavarty <pbadari@us.ibm.com>
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Description:
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The /sys/devices/system/memory contains a snapshot of the
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internal state of the kernel memory blocks. Files could be
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added or removed dynamically to represent hot-add/remove
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operations.
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Users: hotplug memory add/remove tools
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https://w3.opensource.ibm.com/projects/powerpc-utils/
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What: /sys/devices/system/memory/memoryX/removable
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Date: June 2008
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Contact: Badari Pulavarty <pbadari@us.ibm.com>
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Description:
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The file /sys/devices/system/memory/memoryX/removable
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indicates whether this memory block is removable or not.
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This is useful for a user-level agent to determine
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identify removable sections of the memory before attempting
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potentially expensive hot-remove memory operation
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Users: hotplug memory remove tools
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https://w3.opensource.ibm.com/projects/powerpc-utils/
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@ -100,6 +100,21 @@ static ssize_t show_mem_phys_index(struct sys_device *dev,
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return sprintf(buf, "%08lx\n", mem->phys_index);
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}
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/*
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* Show whether the section of memory is likely to be hot-removable
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*/
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static ssize_t show_mem_removable(struct sys_device *dev, char *buf)
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{
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unsigned long start_pfn;
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int ret;
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struct memory_block *mem =
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container_of(dev, struct memory_block, sysdev);
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start_pfn = section_nr_to_pfn(mem->phys_index);
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ret = is_mem_section_removable(start_pfn, PAGES_PER_SECTION);
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return sprintf(buf, "%d\n", ret);
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}
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/*
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* online, offline, going offline, etc.
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*/
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@ -262,6 +277,7 @@ static ssize_t show_phys_device(struct sys_device *dev,
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static SYSDEV_ATTR(phys_index, 0444, show_mem_phys_index, NULL);
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static SYSDEV_ATTR(state, 0644, show_mem_state, store_mem_state);
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static SYSDEV_ATTR(phys_device, 0444, show_phys_device, NULL);
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static SYSDEV_ATTR(removable, 0444, show_mem_removable, NULL);
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#define mem_create_simple_file(mem, attr_name) \
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sysdev_create_file(&mem->sysdev, &attr_##attr_name)
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@ -350,6 +366,8 @@ static int add_memory_block(unsigned long node_id, struct mem_section *section,
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ret = mem_create_simple_file(mem, state);
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if (!ret)
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ret = mem_create_simple_file(mem, phys_device);
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if (!ret)
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ret = mem_create_simple_file(mem, removable);
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return ret;
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}
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@ -394,6 +412,7 @@ int remove_memory_block(unsigned long node_id, struct mem_section *section,
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mem_remove_simple_file(mem, phys_index);
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mem_remove_simple_file(mem, state);
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mem_remove_simple_file(mem, phys_device);
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mem_remove_simple_file(mem, removable);
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unregister_memory(mem, section);
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return 0;
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@ -199,6 +199,18 @@ extern int walk_memory_resource(unsigned long start_pfn,
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unsigned long nr_pages, void *arg,
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int (*func)(unsigned long, unsigned long, void *));
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#ifdef CONFIG_MEMORY_HOTREMOVE
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extern int is_mem_section_removable(unsigned long pfn, unsigned long nr_pages);
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#else
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static inline int is_mem_section_removable(unsigned long pfn,
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unsigned long nr_pages)
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{
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return 0;
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}
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#endif /* CONFIG_MEMORY_HOTREMOVE */
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extern int add_memory(int nid, u64 start, u64 size);
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extern int arch_add_memory(int nid, u64 start, u64 size);
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extern int remove_memory(u64 start, u64 size);
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@ -522,6 +522,66 @@ error:
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EXPORT_SYMBOL_GPL(add_memory);
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#ifdef CONFIG_MEMORY_HOTREMOVE
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/*
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* A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
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* set and the size of the free page is given by page_order(). Using this,
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* the function determines if the pageblock contains only free pages.
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* Due to buddy contraints, a free page at least the size of a pageblock will
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* be located at the start of the pageblock
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*/
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static inline int pageblock_free(struct page *page)
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{
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return PageBuddy(page) && page_order(page) >= pageblock_order;
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}
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/* Return the start of the next active pageblock after a given page */
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static struct page *next_active_pageblock(struct page *page)
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{
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int pageblocks_stride;
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/* Ensure the starting page is pageblock-aligned */
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BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1));
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/* Move forward by at least 1 * pageblock_nr_pages */
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pageblocks_stride = 1;
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/* If the entire pageblock is free, move to the end of free page */
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if (pageblock_free(page))
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pageblocks_stride += page_order(page) - pageblock_order;
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return page + (pageblocks_stride * pageblock_nr_pages);
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}
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/* Checks if this range of memory is likely to be hot-removable. */
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int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
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{
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int type;
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struct page *page = pfn_to_page(start_pfn);
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struct page *end_page = page + nr_pages;
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/* Check the starting page of each pageblock within the range */
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for (; page < end_page; page = next_active_pageblock(page)) {
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type = get_pageblock_migratetype(page);
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/*
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* A pageblock containing MOVABLE or free pages is considered
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* removable
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*/
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if (type != MIGRATE_MOVABLE && !pageblock_free(page))
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return 0;
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/*
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* A pageblock starting with a PageReserved page is not
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* considered removable.
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*/
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if (PageReserved(page))
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return 0;
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}
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/* All pageblocks in the memory block are likely to be hot-removable */
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return 1;
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}
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/*
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* Confirm all pages in a range [start, end) is belongs to the same zone.
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*/
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