lkml.org 
[lkml]   [2015]   [Mar]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] add generic callbacks into compaction
Date
I sent a patch about page allocation for less fragmentation.
http://permalink.gmane.org/gmane.linux.kernel.mm/130599

It proposes a page allocator allocates pages in the same pageblock
for the drivers to move their unmovable pages. Some drivers which comsumes many pages
and increases system fragmentation use the allocator to move their pages to
decrease fragmentation.

I think I can try another approach.
There is a compaction code for balloon pages.
But the compaction code cannot migrate pages of other drivers.
If there is a generic migration framework applicable to any drivers,
drivers can register their migration functions.
And the compaction can migrate movable pages and also driver's pages.

I'm not familiar with virtualization so I couldn't test this patch yet.
But if mm developers agree with this approach, I will complete this patch.

I would do appreciate any feedback.

Signed-off-by: Gioh Kim <gioh.kim@lge.com>
---
drivers/virtio/virtio_balloon.c | 2 ++
include/linux/balloon_compaction.h | 23 +++++++++---
include/linux/fs.h | 3 ++
include/linux/pagemap.h | 26 ++++++++++++++
mm/balloon_compaction.c | 68 ++++++++++++++++++++++++++++++++++--
mm/compaction.c | 7 ++--
mm/migrate.c | 24 ++++++-------
7 files changed, 129 insertions(+), 24 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 0413157..cd9b8e4 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -486,6 +486,8 @@ static int virtballoon_probe(struct virtio_device *vdev)

balloon_devinfo_init(&vb->vb_dev_info);
#ifdef CONFIG_BALLOON_COMPACTION
+ vb->vb_dev_info.mapping = balloon_mapping_alloc(&vb->vb_dev_info,
+ &balloon_aops);
vb->vb_dev_info.migratepage = virtballoon_migratepage;
#endif

diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
index 9b0a15d..0af32b3 100644
--- a/include/linux/balloon_compaction.h
+++ b/include/linux/balloon_compaction.h
@@ -62,6 +62,7 @@ struct balloon_dev_info {
struct list_head pages; /* Pages enqueued & handled to Host */
int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
struct page *page, enum migrate_mode mode);
+ struct address_space *mapping;
};

extern struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info);
@@ -76,10 +77,22 @@ static inline void balloon_devinfo_init(struct balloon_dev_info *balloon)
}

#ifdef CONFIG_BALLOON_COMPACTION
-extern bool balloon_page_isolate(struct page *page);
-extern void balloon_page_putback(struct page *page);
-extern int balloon_page_migrate(struct page *newpage,
- struct page *page, enum migrate_mode mode);
+extern const struct address_space_operations balloon_aops;
+extern int balloon_page_isolate(struct page *page);
+extern int balloon_page_putback(struct page *page);
+extern int balloon_page_migrate(struct address_space *mapping,
+ struct page *newpage,
+ struct page *page,
+ enum migrate_mode mode);
+
+extern struct address_space
+*balloon_mapping_alloc(struct balloon_dev_info *b_dev_info,
+ const struct address_space_operations *a_ops);
+
+static inline void balloon_mapping_free(struct address_space *balloon_mapping)
+{
+ kfree(balloon_mapping);
+}

/*
* __is_movable_balloon_page - helper to perform @page PageBalloon tests
@@ -123,6 +136,7 @@ static inline bool isolated_balloon_page(struct page *page)
static inline void balloon_page_insert(struct balloon_dev_info *balloon,
struct page *page)
{
+ page->mapping = balloon->mapping;
__SetPageBalloon(page);
SetPagePrivate(page);
set_page_private(page, (unsigned long)balloon);
@@ -139,6 +153,7 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon,
*/
static inline void balloon_page_delete(struct page *page)
{
+ page->mapping = NULL;
__ClearPageBalloon(page);
set_page_private(page, 0);
if (PagePrivate(page)) {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b4d71b5..de463b9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -368,6 +368,9 @@ struct address_space_operations {
*/
int (*migratepage) (struct address_space *,
struct page *, struct page *, enum migrate_mode);
+ int (*isolatepage)(struct page *);
+ int (*putbackpage)(struct page *);
+
int (*launder_page) (struct page *);
int (*is_partially_uptodate) (struct page *, unsigned long,
unsigned long);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 4b3736f..715b5b2 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -25,6 +25,7 @@ enum mapping_flags {
AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */
AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */
AS_EXITING = __GFP_BITS_SHIFT + 4, /* final truncate in progress */
+ AS_MIGRATABLE = __GFP_BITS_SHIFT + 5,
};

static inline void mapping_set_error(struct address_space *mapping, int error)
@@ -54,6 +55,31 @@ static inline int mapping_unevictable(struct address_space *mapping)
return !!mapping;
}

+static inline void mapping_set_migratable(struct address_space *mapping)
+{
+ set_bit(AS_MIGRATABLE, &mapping->flags);
+}
+
+static inline void mapping_clear_migratable(struct address_space *mapping)
+{
+ clear_bit(AS_MIGRATABLE, &mapping->flags);
+}
+
+static inline int __mapping_ops(struct address_space *mapping)
+{
+ return mapping->a_ops &&
+ mapping->a_ops->migratepage &&
+ mapping->a_ops->isolatepage &&
+ mapping->a_ops->putbackpage;
+}
+
+static inline int mapping_migratable(struct address_space *mapping)
+{
+ if (mapping && __mapping_ops(mapping))
+ return test_bit(AS_MIGRATABLE, &mapping->flags);
+ return !!mapping;
+}
+
static inline void mapping_set_exiting(struct address_space *mapping)
{
set_bit(AS_EXITING, &mapping->flags);
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index fcad832..2e9d635 100644
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -131,8 +131,11 @@ static inline void __putback_balloon_page(struct page *page)
}

/* __isolate_lru_page() counterpart for a ballooned page */
-bool balloon_page_isolate(struct page *page)
+int balloon_page_isolate(struct page *page)
{
+ if (!balloon_page_movable(page))
+ return false;
+
/*
* Avoid burning cycles with pages that are yet under __free_pages(),
* or just got freed under us.
@@ -173,8 +176,11 @@ bool balloon_page_isolate(struct page *page)
}

/* putback_lru_page() counterpart for a ballooned page */
-void balloon_page_putback(struct page *page)
+int balloon_page_putback(struct page *page)
{
+ if (!isolated_balloon_page(page))
+ return 0;
+
/*
* 'lock_page()' stabilizes the page and prevents races against
* concurrent isolation threads attempting to re-isolate it.
@@ -190,15 +196,20 @@ void balloon_page_putback(struct page *page)
dump_page(page, "not movable balloon page");
}
unlock_page(page);
+ return 0;
}

/* move_to_new_page() counterpart for a ballooned page */
-int balloon_page_migrate(struct page *newpage,
+int balloon_page_migrate(struct address_space *mapping,
+ struct page *newpage,
struct page *page, enum migrate_mode mode)
{
struct balloon_dev_info *balloon = balloon_page_device(page);
int rc = -EAGAIN;

+ if (!isolated_balloon_page(page))
+ return 0;
+
/*
* Block others from accessing the 'newpage' when we get around to
* establishing additional references. We should be the only one
@@ -218,4 +229,55 @@ int balloon_page_migrate(struct page *newpage,
unlock_page(newpage);
return rc;
}
+
+/* define the balloon_mapping->a_ops callback to allow balloon page migration */
+const struct address_space_operations balloon_aops = {
+ .migratepage = balloon_page_migrate,
+ .isolatepage = balloon_page_isolate,
+ .putbackpage = balloon_page_putback,
+};
+EXPORT_SYMBOL_GPL(balloon_aops);
+
+struct address_space *balloon_mapping_alloc(struct balloon_dev_info *b_dev_info,
+ const struct address_space_operations *a_ops)
+{
+ struct address_space *mapping;
+
+ mapping = kmalloc(sizeof(*mapping), GFP_KERNEL);
+ if (!mapping)
+ return ERR_PTR(-ENOMEM);
+
+ /*
+ * Give a clean 'zeroed' status to all elements of this special
+ * balloon page->mapping struct address_space instance.
+ */
+ address_space_init_once(mapping);
+
+ /*
+ * Set mapping->flags appropriately, to allow balloon pages
+ * ->mapping identification.
+ */
+ mapping_set_migratable(mapping);
+ mapping_set_gfp_mask(mapping, balloon_mapping_gfp_mask());
+
+ /* balloon's page->mapping->a_ops callback descriptor */
+ mapping->a_ops = a_ops;
+
+ /*
+ * Establish a pointer reference back to the balloon device descriptor
+ * this particular page->mapping will be servicing.
+ * This is used by compaction / migration procedures to identify and
+ * access the balloon device pageset while isolating / migrating pages.
+ *
+ * As some balloon drivers can register multiple balloon devices
+ * for a single guest, this also helps compaction / migration to
+ * properly deal with multiple balloon pagesets, when required.
+ */
+ mapping->private_data = b_dev_info;
+ b_dev_info->mapping = mapping;
+
+ return mapping;
+}
+EXPORT_SYMBOL_GPL(balloon_mapping_alloc);
+
#endif /* CONFIG_BALLOON_COMPACTION */
diff --git a/mm/compaction.c b/mm/compaction.c
index 8c0d945..9fbcb7b 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -740,12 +740,9 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
* Skip any other type of page
*/
if (!PageLRU(page)) {
- if (unlikely(balloon_page_movable(page))) {
- if (balloon_page_isolate(page)) {
- /* Successfully isolated */
+ if (mapping_migratable(page->mapping))
+ if (page->mapping->a_ops->isolatepage(page))
goto isolate_success;
- }
- }
continue;
}

diff --git a/mm/migrate.c b/mm/migrate.c
index 85e0426..37cb366 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -71,6 +71,12 @@ int migrate_prep_local(void)
return 0;
}

+static bool isolated_migratable_page(struct page *page)
+{
+ return page_mapped(page) == 0 &&
+ mapping_migratable(page->mapping);
+}
+
/*
* Put previously isolated pages back onto the appropriate lists
* from where they were once taken off for compaction/migration.
@@ -91,9 +97,9 @@ void putback_movable_pages(struct list_head *l)
}
list_del(&page->lru);
dec_zone_page_state(page, NR_ISOLATED_ANON +
- page_is_file_cache(page));
- if (unlikely(isolated_balloon_page(page)))
- balloon_page_putback(page);
+ page_is_file_cache(page));
+ if (unlikely(isolated_migratable_page(page)))
+ page->mapping->a_ops->putbackpage(page);
else
putback_lru_page(page);
}
@@ -843,15 +849,9 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
}
}

- if (unlikely(isolated_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, and perform
- * the page migration right away (proteced by page lock).
- */
- rc = balloon_page_migrate(newpage, page, mode);
+ if (unlikely(isolated_migratable_page(page))) {
+ rc = page->mapping->a_ops->migratepage(page->mapping,
+ newpage, page, mode);
goto out_unlock;
}

--
1.7.9.5


\
 
 \ /
  Last update: 2015-04-01 01:41    [W:0.065 / U:0.668 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site