On Tue, 31 Aug 2010 22:36:49 +0800
Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
> On Tue, Aug 31, 2010 at 10:19:42PM +0800, Wu Fengguang wrote:
> > On Mon, Aug 23, 2010 at 05:22:46PM +0800, Michal Hocko wrote:
> > > On Sun 22-08-10 08:42:32, Wu Fengguang wrote:
> > > > Hi Michal,
> > >
> > > Hi,
> > >
> > > >
> > > > It helps to explain in changelog/code
> > > >
> > > > - in what situation a ZONE_MOVABLE will contain !MIGRATE_MOVABLE
> > > > pages?
> > >
> > > page can be MIGRATE_RESERVE IIUC.
> >
> > Yup, it may also be set to MIGRATE_ISOLATE by soft_offline_page().
>
> Ah a non-movable page allocation could fall back into the movable
> zone. See __rmqueue_fallback() and the fallbacks[][] array. So the
>
> if (type != MIGRATE_MOVABLE && !pageblock_free(page))
>
> check in is_mem_section_removable() is correct. It is
> set_migratetype_isolate() that should be fixed to use the same check.
>
Here is a patch for set_migratetype_isolate(). This is not a _fix_ but an
improvement.
==
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
At memory hotplug, we set pageblock's movable-type as ISOLATE. At failure,
we make it back to be MOVABLE. So,
- pageblock's type shoule be movable before isolation.
- pageblock's contents should be really movable before isolation.
Add document about it and add pageblock_free() call for fast-path.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
include/linux/mmzone.h | 4 ++++
mm/memory_hotplug.c | 2 +-
mm/page_alloc.c | 17 +++++++++++++----
3 files changed, 18 insertions(+), 5 deletions(-)
Index: mmotm-0827/mm/page_alloc.c
===================================================================
--- mmotm-0827.orig/mm/page_alloc.c
+++ mmotm-0827/mm/page_alloc.c
@@ -5282,19 +5282,28 @@ int set_migratetype_isolate(struct page
unsigned long immobile = 0;
struct memory_isolate_notify arg;
int notifier_ret;
- int ret = -EBUSY;
+ int ret = 0;
int zone_idx;
zone = page_zone(page);
zone_idx = zone_idx(zone);
spin_lock_irqsave(&zone->lock, flags);
+ /*
+ * At failure of hotplug, we turns this block to be MOVABLE if
+ * isolation has been successfully done. So, if page-block is movable
+ * or freed, we can try this without check contents..
+ */
if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE ||
- zone_idx == ZONE_MOVABLE) {
- ret = 0;
+ pageblock_free(page) ||
+ zone_idx == ZONE_MOVABLE)
goto out;
- }
+ ret = -EBUSY;
+ /*
+ * check contents, because we move this pageblocks type to be MOVABLE
+ * at failure, the contents should be movable.
+ */
pfn = page_to_pfn(page);
arg.start_pfn = pfn;
arg.nr_pages = pageblock_nr_pages;
Index: mmotm-0827/include/linux/mmzone.h
===================================================================
--- mmotm-0827.orig/include/linux/mmzone.h
+++ mmotm-0827/include/linux/mmzone.h
@@ -54,6 +54,10 @@ static inline int get_pageblock_migratet
return get_pageblock_flags_group(page, PB_migrate, PB_migrate_end);
}
+#ifdef CONFIG_MEMORY_HOTREMOVE
+extern int pageblock_free(struct page *page);
+#endif
+
struct free_area {
struct list_head free_list[MIGRATE_TYPES];
unsigned long nr_free;
Index: mmotm-0827/mm/memory_hotplug.c
===================================================================
--- mmotm-0827.orig/mm/memory_hotplug.c
+++ mmotm-0827/mm/memory_hotplug.c
@@ -576,7 +576,7 @@ EXPORT_SYMBOL_GPL(add_memory);
* 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)
+int pageblock_free(struct page *page)
{
return PageBuddy(page) && page_order(page) >= pageblock_order;
}
--
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