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Subject[PATCH] memory unplug v7 [5/6] - page offline
Changes V5 ->V6
- style fixes.


Logic.
- set all pages in [start,end) as isolated migration-type.
by this, all free pages in the range will be not-for-use.
- Migrate all LRU pages in the range.
- Test all pages in the range's refcnt is zero or not.

Todo:
- allocate migration destination page from better area.
- confirm page_count(page)== 0 && PageReserved(page) page is safe to be freed..
(I don't like this kind of page but..
- Find out pages which cannot be migrated.
- more running tests.
- Use reclaim for unplugging other memory type area.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>

---
include/linux/kernel.h | 1
include/linux/memory_hotplug.h | 5
mm/Kconfig | 5
mm/memory_hotplug.c | 254 +++++++++++++++++++++++++++++++++++++++++
mm/page_alloc.c | 47 +++++++
5 files changed, 311 insertions(+), 1 deletion(-)
Index: linux-2.6.22-rc6-mm1/mm/Kconfig
===================================================================
--- linux-2.6.22-rc6-mm1.orig/mm/Kconfig
+++ linux-2.6.22-rc6-mm1/mm/Kconfig
@@ -126,6 +126,11 @@ config MEMORY_HOTPLUG_SPARSE
def_bool y
depends on SPARSEMEM && MEMORY_HOTPLUG

+config MEMORY_HOTREMOVE
+ bool "Allow for memory hot remove"
+ depends on MEMORY_HOTPLUG
+ depends on MIGRATION
+
# Heavily threaded applications may benefit from splitting the mm-wide
# page_table_lock, so that faults on different parts of the user address
# space can be handled with less contention: split it at this NR_CPUS.
Index: linux-2.6.22-rc6-mm1/mm/memory_hotplug.c
===================================================================
--- linux-2.6.22-rc6-mm1.orig/mm/memory_hotplug.c
+++ linux-2.6.22-rc6-mm1/mm/memory_hotplug.c
@@ -23,6 +23,9 @@
#include <linux/vmalloc.h>
#include <linux/ioport.h>
#include <linux/cpuset.h>
+#include <linux/delay.h>
+#include <linux/migrate.h>
+#include <linux/page-isolation.h>

#include <asm/tlbflush.h>

@@ -301,3 +304,254 @@ error:
return ret;
}
EXPORT_SYMBOL_GPL(add_memory);
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+/*
+ * 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)
+{
+ unsigned long pfn;
+ struct zone *zone = NULL;
+ struct page *page;
+ int i;
+ for (pfn = start_pfn;
+ pfn < end_pfn;
+ pfn += MAX_ORDER_NR_PAGES) {
+ i = 0;
+ /* This is just a CONFIG_HOLES_IN_ZONE check.*/
+ while ((i < MAX_ORDER_NR_PAGES) && !pfn_valid_within(pfn + i))
+ i++;
+ if (i == MAX_ORDER_NR_PAGES)
+ continue;
+ page = pfn_to_page(pfn + i);
+ if (zone && page_zone(page) != zone)
+ return 0;
+ zone = page_zone(page);
+ }
+ return 1;
+}
+
+/*
+ * Scanning pfn is much easier than scanning lru list.
+ * Scan pfn from start to end and Find LRU page.
+ */
+int scan_lru_pages(unsigned long start, unsigned long end)
+{
+ unsigned long pfn;
+ struct page *page;
+ for (pfn = start; pfn < end; pfn++) {
+ if (pfn_valid(pfn)) {
+ page = pfn_to_page(pfn);
+ if (PageLRU(page))
+ return pfn;
+ }
+ }
+ return 0;
+}
+
+static struct page *
+hotremove_migrate_alloc(struct page *page,
+ unsigned long private,
+ int **x)
+{
+ /* This should be improoooooved!! */
+ return alloc_page(GFP_HIGHUSER_PAGECACHE);
+}
+
+
+#define NR_OFFLINE_AT_ONCE_PAGES (256)
+static int
+do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
+{
+ unsigned long pfn;
+ struct page *page;
+ int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
+ int not_managed = 0;
+ int ret = 0;
+ LIST_HEAD(source);
+
+ for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
+ if (!pfn_valid(pfn))
+ continue;
+ page = pfn_to_page(pfn);
+ if (!page_count(page))
+ continue;
+ /*
+ * We can skip free pages. And we can only deal with pages on
+ * LRU.
+ */
+ ret = isolate_lru_page(page, &source);
+ if (!ret) { /* Success */
+ move_pages--;
+ } else {
+ /* Becasue we don't have big zone->lock. we should
+ check this again here. */
+ if (page_count(page))
+ not_managed++;
+#ifdef CONFIG_DEBUG_VM
+ printk(KERN_INFO "removing from LRU failed"
+ " %lx/%d/%lx\n",
+ pfn, page_count(page), page->flags);
+#endif
+ }
+ }
+ ret = -EBUSY;
+ if (not_managed) {
+ if (!list_empty(&source))
+ putback_lru_pages(&source);
+ goto out;
+ }
+ ret = 0;
+ if (list_empty(&source))
+ goto out;
+ /* this function returns # of failed pages */
+ ret = migrate_pages(&source, hotremove_migrate_alloc, 0);
+
+out:
+ return ret;
+}
+
+/*
+ * remove from free_area[] and mark all as Reserved.
+ */
+static int
+offline_isolated_pages_cb(unsigned long start, unsigned long nr_pages,
+ void *data)
+{
+ __offline_isolated_pages(start, start + nr_pages);
+ return 0;
+}
+
+static void
+offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
+{
+ walk_memory_resource(start_pfn, end_pfn - start_pfn, NULL,
+ offline_isolated_pages_cb);
+}
+
+/*
+ * Check all pages in range, recoreded as memory resource, are isolated.
+ */
+static int
+check_pages_isolated_cb(unsigned long start_pfn, unsigned long nr_pages,
+ void *data)
+{
+ int ret;
+ long offlined = *(long *)data;
+ ret = test_pages_isolated(start_pfn, start_pfn + nr_pages);
+ offlined = nr_pages;
+ if (!ret)
+ *(long *)data += offlined;
+ return ret;
+}
+
+static long
+check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
+{
+ long offlined = 0;
+ int ret;
+
+ ret = walk_memory_resource(start_pfn, end_pfn - start_pfn, &offlined,
+ check_pages_isolated_cb);
+ if (ret < 0)
+ offlined = (long)ret;
+ return offlined;
+}
+
+extern void drain_all_local_pages(void);
+
+int offline_pages(unsigned long start_pfn,
+ unsigned long end_pfn, unsigned long timeout)
+{
+ unsigned long pfn, nr_pages, expire;
+ long offlined_pages;
+ int ret, drain, retry_max;
+ struct zone *zone;
+
+ BUG_ON(start_pfn >= end_pfn);
+ /* at least, alignment against pageblock is necessary */
+ if (!IS_ALIGNED(start_pfn, pageblock_nr_pages))
+ return -EINVAL;
+ if (!IS_ALIGNED(end_pfn, pageblock_nr_pages))
+ return -EINVAL;
+ /* This makes hotplug much easier...and readable.
+ we assume this for now. .*/
+ if (!test_pages_in_a_zone(start_pfn, end_pfn))
+ return -EINVAL;
+ /* set above range as isolated */
+ ret = start_isolate_page_range(start_pfn, end_pfn);
+ if (ret)
+ return ret;
+ nr_pages = end_pfn - start_pfn;
+ pfn = start_pfn;
+ expire = jiffies + timeout;
+ drain = 0;
+ retry_max = 5;
+repeat:
+ /* start memory hot removal */
+ ret = -EAGAIN;
+ if (time_after(jiffies, expire))
+ goto failed_removal;
+ ret = -EINTR;
+ if (signal_pending(current))
+ goto failed_removal;
+ ret = 0;
+ if (drain) {
+ lru_add_drain_all();
+ flush_scheduled_work();
+ cond_resched();
+ drain_all_local_pages();
+ }
+
+ pfn = scan_lru_pages(start_pfn, end_pfn);
+ if (pfn) { /* We have page on LRU */
+ ret = do_migrate_range(pfn, end_pfn);
+ if (!ret) {
+ drain = 1;
+ goto repeat;
+ } else {
+ if (ret < 0)
+ if (--retry_max == 0)
+ goto failed_removal;
+ yield();
+ drain = 1;
+ goto repeat;
+ }
+ }
+ /* drain all zone's lru pagevec, this is asyncronous... */
+ lru_add_drain_all();
+ flush_scheduled_work();
+ yield();
+ /* drain pcp pages , this is synchrouns. */
+ drain_all_local_pages();
+ /* check again */
+ offlined_pages = check_pages_isolated(start_pfn, end_pfn);
+ if (offlined_pages < 0) {
+ ret = -EBUSY;
+ goto failed_removal;
+ }
+ printk(KERN_INFO "Offlined Pages %ld\n", offlined_pages);
+ /* Ok, all of our target is islaoted.
+ We cannot do rollback at this point. */
+ offline_isolated_pages(start_pfn, end_pfn);
+ /* reset pagetype flags */
+ start_isolate_page_range(start_pfn, end_pfn);
+ /* removal success */
+ zone = page_zone(pfn_to_page(start_pfn));
+ zone->present_pages -= offlined_pages;
+ zone->zone_pgdat->node_present_pages -= offlined_pages;
+ totalram_pages -= offlined_pages;
+ num_physpages -= offlined_pages;
+ vm_total_pages = nr_free_pagecache_pages();
+ writeback_set_ratelimit();
+ return 0;
+
+failed_removal:
+ printk(KERN_INFO "memory offlining %lx to %lx failed\n",
+ start_pfn, end_pfn);
+ /* pushback to free area */
+ undo_isolate_page_range(start_pfn, end_pfn);
+ return ret;
+}
+#endif /* CONFIG_MEMORY_HOTREMOVE */
Index: linux-2.6.22-rc6-mm1/include/linux/memory_hotplug.h
===================================================================
--- linux-2.6.22-rc6-mm1.orig/include/linux/memory_hotplug.h
+++ linux-2.6.22-rc6-mm1/include/linux/memory_hotplug.h
@@ -59,7 +59,10 @@ extern int add_one_highpage(struct page
extern void online_page(struct page *page);
/* VM interface that may be used by firmware interface */
extern int online_pages(unsigned long, unsigned long);
-
+#ifdef CONFIG_MEMORY_HOTREMOVE
+extern int offline_pages(unsigned long, unsigned long, unsigned long);
+extern void __offline_isolated_pages(unsigned long, unsigned long);
+#endif
/* reasonably generic interface to expand the physical pages in a zone */
extern int __add_pages(struct zone *zone, unsigned long start_pfn,
unsigned long nr_pages);
Index: linux-2.6.22-rc6-mm1/mm/page_alloc.c
===================================================================
--- linux-2.6.22-rc6-mm1.orig/mm/page_alloc.c
+++ linux-2.6.22-rc6-mm1/mm/page_alloc.c
@@ -4456,3 +4456,50 @@ void unset_migratetype_isolate(struct pa
out:
spin_unlock_irqrestore(&zone->lock, flags);
}
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+/*
+ * All pages in the range must be isolated before calling this.
+ */
+void
+__offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
+{
+ struct page *page;
+ struct zone *zone;
+ int order, i;
+ unsigned long pfn;
+ unsigned long flags;
+ /* find the first valid pfn */
+ for (pfn = start_pfn; pfn < end_pfn; pfn++)
+ if (pfn_valid(pfn))
+ break;
+ if (pfn == end_pfn)
+ return;
+ zone = page_zone(pfn_to_page(pfn));
+ spin_lock_irqsave(&zone->lock, flags);
+ pfn = start_pfn;
+ while (pfn < end_pfn) {
+ if (!pfn_valid(pfn)) {
+ pfn++;
+ continue;
+ }
+ page = pfn_to_page(pfn);
+ BUG_ON(page_count(page));
+ BUG_ON(!PageBuddy(page));
+ order = page_order(page);
+#ifdef CONFIG_DEBUG_VM
+ printk(KERN_INFO "remove from free list %lx %d %lx\n",
+ pfn, 1 << order, end_pfn);
+#endif
+ list_del(&page->lru);
+ rmv_page_order(page);
+ zone->free_area[order].nr_free--;
+ __mod_zone_page_state(zone, NR_FREE_PAGES,
+ - (1UL << order));
+ for (i = 0; i < (1 << order); i++)
+ SetPageReserved((page+i));
+ pfn += (1 << order);
+ }
+ spin_unlock_irqrestore(&zone->lock, flags);
+}
+#endif
Index: linux-2.6.22-rc6-mm1/include/linux/kernel.h
===================================================================
--- linux-2.6.22-rc6-mm1.orig/include/linux/kernel.h
+++ linux-2.6.22-rc6-mm1/include/linux/kernel.h
@@ -34,6 +34,7 @@ extern const char linux_proc_banner[];

#define ALIGN(x,a) __ALIGN_MASK(x,(typeof(x))(a)-1)
#define __ALIGN_MASK(x,mask) (((x)+(mask))&~(mask))
+#define IS_ALIGNED(x,a) (((x) % ((typeof(x))(a))) == 0)

#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))

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