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Date: Thu, 28 Jun 2012 18:49:39 -0300
From: Rafael Aquini <aquini@...hat.com>
To: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
Rusty Russell <rusty@...tcorp.com.au>,
"Michael S. Tsirkin" <mst@...hat.com>,
Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
Andi Kleen <andi@...stfloor.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Rafael Aquini <aquini@...hat.com>
Subject: [PATCH v2 1/4] mm: introduce compaction and migration for virtio ballooned pages
This patch introduces the helper functions as well as the necessary changes
to teach compaction and migration bits how to cope with pages which are
part of a guest memory balloon, in order to make them movable by memory
compaction procedures.
Signed-off-by: Rafael Aquini <aquini@...hat.com>
---
include/linux/mm.h | 16 ++++++++
mm/compaction.c | 110 +++++++++++++++++++++++++++++++++++++++++++---------
mm/migrate.c | 30 +++++++++++++-
3 files changed, 136 insertions(+), 20 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index b36d08c..35568fc 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1629,5 +1629,21 @@ static inline unsigned int debug_guardpage_minorder(void) { return 0; }
static inline bool page_is_guard(struct page *page) { return false; }
#endif /* CONFIG_DEBUG_PAGEALLOC */
+#if (defined(CONFIG_VIRTIO_BALLOON) || \
+ defined(CONFIG_VIRTIO_BALLOON_MODULE)) && defined(CONFIG_COMPACTION)
+extern bool isolate_balloon_page(struct page *);
+extern bool putback_balloon_page(struct page *);
+extern struct address_space *balloon_mapping;
+
+static inline bool is_balloon_page(struct page *page)
+{
+ return (page->mapping == balloon_mapping) ? true : false;
+}
+#else
+static inline bool is_balloon_page(struct page *page) { return false; }
+static inline bool isolate_balloon_page(struct page *page) { return false; }
+static inline bool putback_balloon_page(struct page *page) { return false; }
+#endif /* (VIRTIO_BALLOON || VIRTIO_BALLOON_MODULE) && COMPACTION */
+
#endif /* __KERNEL__ */
#endif /* _LINUX_MM_H */
diff --git a/mm/compaction.c b/mm/compaction.c
index 7ea259d..6c6e572 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -14,6 +14,7 @@
#include <linux/backing-dev.h>
#include <linux/sysctl.h>
#include <linux/sysfs.h>
+#include <linux/export.h>
#include "internal.h"
#if defined CONFIG_COMPACTION || defined CONFIG_CMA
@@ -312,32 +313,40 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
continue;
}
- if (!PageLRU(page))
- continue;
-
/*
- * PageLRU is set, and lru_lock excludes isolation,
- * splitting and collapsing (collapsing has already
- * happened if PageLRU is set).
+ * It is possible to migrate LRU pages and balloon pages.
+ * Skip any other type of page.
*/
- if (PageTransHuge(page)) {
- low_pfn += (1 << compound_order(page)) - 1;
- continue;
- }
+ if (likely(PageLRU(page))) {
+ /*
+ * PageLRU is set, and lru_lock excludes isolation,
+ * splitting and collapsing (collapsing has already
+ * happened if PageLRU is set).
+ */
+ if (PageTransHuge(page)) {
+ low_pfn += (1 << compound_order(page)) - 1;
+ continue;
+ }
- if (!cc->sync)
- mode |= ISOLATE_ASYNC_MIGRATE;
+ if (!cc->sync)
+ mode |= ISOLATE_ASYNC_MIGRATE;
- lruvec = mem_cgroup_page_lruvec(page, zone);
+ lruvec = mem_cgroup_page_lruvec(page, zone);
- /* Try isolate the page */
- if (__isolate_lru_page(page, mode) != 0)
- continue;
+ /* Try isolate the page */
+ if (__isolate_lru_page(page, mode) != 0)
+ continue;
- VM_BUG_ON(PageTransCompound(page));
+ VM_BUG_ON(PageTransCompound(page));
+
+ /* Successfully isolated */
+ del_page_from_lru_list(page, lruvec, page_lru(page));
+ } else if (is_balloon_page(page)) {
+ if (!isolate_balloon_page(page))
+ continue;
+ } else
+ continue;
- /* Successfully isolated */
- del_page_from_lru_list(page, lruvec, page_lru(page));
list_add(&page->lru, migratelist);
cc->nr_migratepages++;
nr_isolated++;
@@ -903,4 +912,67 @@ void compaction_unregister_node(struct node *node)
}
#endif /* CONFIG_SYSFS && CONFIG_NUMA */
+#if defined(CONFIG_VIRTIO_BALLOON) || defined(CONFIG_VIRTIO_BALLOON_MODULE)
+/*
+ * Balloon pages special page->mapping.
+ * users must properly allocate and initialize an instance of balloon_mapping,
+ * and set it as the page->mapping for balloon enlisted page instances.
+ *
+ * address_space_operations necessary methods for ballooned pages:
+ * .migratepage - used to perform balloon's page migration (as is)
+ * .invalidatepage - used to isolate a page from balloon's page list
+ * .freepage - used to reinsert an isolated page to balloon's page list
+ */
+struct address_space *balloon_mapping;
+EXPORT_SYMBOL_GPL(balloon_mapping);
+
+/* __isolate_lru_page() counterpart for a ballooned page */
+bool isolate_balloon_page(struct page *page)
+{
+ if (WARN_ON(!is_balloon_page(page)))
+ return false;
+
+ if (likely(get_page_unless_zero(page))) {
+ /*
+ * We can race against move_to_new_page() & __unmap_and_move().
+ * If we stumble across a locked balloon page and succeed on
+ * isolating it, the result tends to be disastrous.
+ */
+ if (likely(trylock_page(page))) {
+ /*
+ * A ballooned page, by default, has just one refcount.
+ * Prevent concurrent compaction threads from isolating
+ * an already isolated balloon page.
+ */
+ if (is_balloon_page(page) && (page_count(page) == 2)) {
+ page->mapping->a_ops->invalidatepage(page, 0);
+ unlock_page(page);
+ return true;
+ }
+ unlock_page(page);
+ }
+ /* Drop refcount taken for this already isolated page */
+ put_page(page);
+ }
+ return false;
+}
+
+/* putback_lru_page() counterpart for a ballooned page */
+bool putback_balloon_page(struct page *page)
+{
+ if (WARN_ON(!is_balloon_page(page)))
+ return false;
+
+ if (likely(trylock_page(page))) {
+ if(is_balloon_page(page)) {
+ page->mapping->a_ops->freepage(page);
+ put_page(page);
+ unlock_page(page);
+ return true;
+ }
+ unlock_page(page);
+ }
+ return false;
+}
+#endif /* CONFIG_VIRTIO_BALLOON || CONFIG_VIRTIO_BALLOON_MODULE */
#endif /* CONFIG_COMPACTION */
diff --git a/mm/migrate.c b/mm/migrate.c
index be26d5c..59c7bc5 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -78,7 +78,10 @@ void putback_lru_pages(struct list_head *l)
list_del(&page->lru);
dec_zone_page_state(page, NR_ISOLATED_ANON +
page_is_file_cache(page));
- putback_lru_page(page);
+ if (unlikely(is_balloon_page(page)))
+ WARN_ON(!putback_balloon_page(page));
+ else
+ putback_lru_page(page);
}
}
@@ -783,6 +786,17 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
}
}
+ if (is_balloon_page(page)) {
+ /*
+ * A ballooned page does not need any special attention from
+ * physical to virtual reverse mapping procedures.
+ * Skip any attempt to unmap PTEs or to remap swap cache,
+ * in order to avoid burning cycles at rmap level.
+ */
+ remap_swapcache = 0;
+ goto skip_unmap;
+ }
+
/*
* Corner case handling:
* 1. When a new swap-cache page is read into, it is added to the LRU
@@ -852,6 +866,20 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
goto out;
rc = __unmap_and_move(page, newpage, force, offlining, mode);
+
+ if (is_balloon_page(newpage)) {
+ /*
+ * A ballooned page has been migrated already. Now, it is the
+ * time to wrap-up counters, handle the old page back to Buddy
+ * and return.
+ */
+ list_del(&page->lru);
+ dec_zone_page_state(page, NR_ISOLATED_ANON +
+ page_is_file_cache(page));
+ put_page(page);
+ __free_page(page);
+ return rc;
+ }
out:
if (rc != -EAGAIN) {
/*
--
1.7.10.2
--
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