Rafael Aquini
2012-Sep-17 16:38 UTC
[PATCH v10 0/5] make balloon pages movable by compaction
Memory fragmentation introduced by ballooning might reduce significantly
the number of 2MB contiguous memory blocks that can be used within a guest,
thus imposing performance penalties associated with the reduced number of
transparent huge pages that could be used by the guest workload.
This patch-set follows the main idea discussed at 2012 LSFMMS session:
"Ballooning for transparent huge pages" --
http://lwn.net/Articles/490114/
to introduce the required changes to the virtio_balloon driver, as well as
the changes to the core compaction & migration bits, in order to make those
subsystems aware of ballooned pages and allow memory balloon pages become
movable within a guest, thus avoiding the aforementioned fragmentation issue
Following are numbers that prove this patch benefits on allowing compaction
to be more effective at memory ballooned guests.
Results for STRESS-HIGHALLOC benchmark, from Mel Gorman's mmtests suite,
running on a 4gB RAM KVM guest which was ballooning 1gB RAM in 256mB chunks,
at every minute (inflating/deflating), while test was running:
===BEGIN stress-highalloc
STRESS-HIGHALLOC
stress-highalloc highalloc-3.6.0
3.6.0-rc5 rc5-patch
Pass 1 47.00 ( 0.00%) 85.00 (38.00%)
Pass 2 52.00 ( 0.00%) 87.00 (35.00%)
while Rested 77.00 ( 0.00%) 99.00 (22.00%)
MMTests Statistics: duration
3.6.0 3.6.0
rc5 rc5-patch
User 1566.87 1066.77
System 948.78 713.19
Elapsed 2008.95 1650.72
MMTests Statistics: vmstat
3.6.0 3.6.0
rc5 rc5-patch
Page Ins 5037962 3458106
Page Outs 10779728 8969512
Swap Ins 34282 5565
Swap Outs 63027 19717
Direct pages scanned 481017 166920
Kswapd pages scanned 2083130 1537202
Kswapd pages reclaimed 1838615 1459932
Direct pages reclaimed 337487 120613
Kswapd efficiency 88% 94%
Kswapd velocity 1036.925 931.231
Direct efficiency 70% 72%
Direct velocity 239.437 101.120
Percentage direct scans 18% 9%
Page writes by reclaim 157305 19855
Page writes file 94278 138
Page writes anon 63027 19717
Page reclaim immediate 111205 64510
Page rescued immediate 0 0
Slabs scanned 3362816 2375680
Direct inode steals 12411 2022
Kswapd inode steals 753789 524457
Kswapd skipped wait 136 7
THP fault alloc 688 739
THP collapse alloc 378 481
THP splits 279 317
THP fault fallback 172 45
THP collapse fail 12 5
Compaction stalls 1378 968
Compaction success 406 595
Compaction failures 972 373
Compaction pages moved 3104073 1790932
Compaction move failure 92713 41252
===END stress-highalloc
Rafael Aquini (5):
mm: introduce a common interface for balloon pages mobility
mm: introduce compaction and migration for ballooned pages
virtio_balloon: introduce migration primitives to balloon pages
mm: introduce putback_movable_pages()
mm: add vm event counters for balloon pages compaction
drivers/virtio/virtio_balloon.c | 306 ++++++++++++++++++++++++++++++++++---
include/linux/balloon_compaction.h | 147 ++++++++++++++++++
include/linux/migrate.h | 2 +
include/linux/pagemap.h | 18 +++
include/linux/vm_event_item.h | 8 +-
mm/Kconfig | 15 ++
mm/Makefile | 1 +
mm/balloon_compaction.c | 154 +++++++++++++++++++
mm/compaction.c | 51 ++++---
mm/migrate.c | 57 ++++++-
mm/page_alloc.c | 2 +-
mm/vmstat.c | 10 +-
12 files changed, 726 insertions(+), 45 deletions(-)
create mode 100644 include/linux/balloon_compaction.h
create mode 100644 mm/balloon_compaction.c
Change log:
v10:
* Adjust leak_balloon() wait_event logic to make a clear locking scheme (MST);
* Drop the RCU protection approach for dereferencing balloon's
page->mapping;
* Minor nitpitcks on code commentaries (MST);
v9:
* Adjust rcu_dereference usage to leverage page lock protection (Paul, Peter);
* Enhance doc on compaction interface introduced to balloon driver (Michael);
* Fix issue with isolated pages breaking leak_balloon() logics (Michael);
v8:
* introduce a common MM interface for balloon driver page compaction (Michael);
* remove the global state preventing multiple balloon device support (Michael);
* introduce RCU protection/syncrhonization to balloon page->mapping
(Michael);
v7:
* fix a potential page leak case at 'putback_balloon_page'
(Mel);
* adjust vm-events-counter patch and remove its drop-on-merge message (Rik);
* add 'putback_movable_pages' to avoid hacks on
'putback_lru_pages' (Minchan);
v6:
* rename 'is_balloon_page()' to 'movable_balloon_page()'
(Rik);
v5:
* address Andrew Morton's review comments on the patch series;
* address a couple extra nitpick suggestions on PATCH 01 (Minchan);
v4:
* address Rusty Russel's review comments on PATCH 02;
* re-base virtio_balloon patch on 9c378abc5c0c6fc8e3acf5968924d274503819b3;
V3:
* address reviewers nitpick suggestions on PATCH 01 (Mel, Minchan);
V2:
* address Mel Gorman's review comments on PATCH 01;
--
1.7.11.4
Rafael Aquini
2012-Sep-17 16:38 UTC
[PATCH v10 1/5] mm: introduce a common interface for balloon pages mobility
Memory fragmentation introduced by ballooning might reduce significantly
the number of 2MB contiguous memory blocks that can be used within a guest,
thus imposing performance penalties associated with the reduced number of
transparent huge pages that could be used by the guest workload.
This patch introduces a common interface to help a balloon driver on
making its page set movable to compaction, and thus allowing the system
to better leverage the compation efforts on memory defragmentation.
Signed-off-by: Rafael Aquini <aquini at redhat.com>
---
include/linux/balloon_compaction.h | 147 +++++++++++++++++++++++++++++++++++
include/linux/pagemap.h | 18 +++++
mm/Kconfig | 15 ++++
mm/Makefile | 1 +
mm/balloon_compaction.c | 152 +++++++++++++++++++++++++++++++++++++
5 files changed, 333 insertions(+)
create mode 100644 include/linux/balloon_compaction.h
create mode 100644 mm/balloon_compaction.c
diff --git a/include/linux/balloon_compaction.h
b/include/linux/balloon_compaction.h
new file mode 100644
index 0000000..1c27a93
--- /dev/null
+++ b/include/linux/balloon_compaction.h
@@ -0,0 +1,147 @@
+/*
+ * include/linux/balloon_compaction.h
+ *
+ * Common interface definitions for making balloon pages movable to compaction.
+ *
+ * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini at
redhat.com>
+ */
+#ifndef _LINUX_BALLOON_COMPACTION_H
+#define _LINUX_BALLOON_COMPACTION_H
+
+#include <linux/rcupdate.h>
+#include <linux/pagemap.h>
+#include <linux/gfp.h>
+#include <linux/err.h>
+
+/* return code to identify when a ballooned page has been migrated */
+#define BALLOON_MIGRATION_RETURN 0xba1100
+
+#ifdef CONFIG_BALLOON_COMPACTION
+#define count_balloon_event(e) count_vm_event(e)
+#define free_balloon_mapping(m) kfree(m)
+
+extern bool isolate_balloon_page(struct page *);
+extern void putback_balloon_page(struct page *);
+extern int migrate_balloon_page(struct page *newpage,
+ struct page *page, enum migrate_mode mode);
+extern struct address_space *alloc_balloon_mapping(void *balloon_device,
+ const struct address_space_operations *a_ops);
+
+static inline void assign_balloon_mapping(struct page *page,
+ struct address_space *mapping)
+{
+ page->mapping = mapping;
+ smp_wmb();
+}
+
+static inline void clear_balloon_mapping(struct page *page)
+{
+ page->mapping = NULL;
+ smp_wmb();
+}
+
+static inline gfp_t balloon_mapping_gfp_mask(void)
+{
+ return GFP_HIGHUSER_MOVABLE;
+}
+
+static inline bool __is_movable_balloon_page(struct page *page)
+{
+ struct address_space *mapping = ACCESS_ONCE(page->mapping);
+ smp_read_barrier_depends();
+ return mapping_balloon(mapping);
+}
+
+/*
+ * movable_balloon_page - test page->mapping->flags to identify balloon
pages
+ * that can be moved by compaction/migration.
+ *
+ * This function is used at core compaction's page isolation scheme and so
it's
+ * exposed to several system pages which may, or may not, be part of a memory
+ * balloon, and thus we cannot afford to hold a page locked to perform tests.
+ *
+ * Therefore, as we might return false positives in the case a balloon page
+ * is just released under us, the page->mapping->flags need to be
retested
+ * with the proper page lock held, on the functions that will cope with the
+ * balloon page later.
+ */
+static inline bool movable_balloon_page(struct page *page)
+{
+ /*
+ * Before dereferencing and testing mapping->flags, lets make sure
+ * this is not a page that uses ->mapping in a different way
+ */
+ if (!PageSlab(page) && !PageSwapCache(page) && !PageAnon(page)
&&
+ !page_mapped(page))
+ return __is_movable_balloon_page(page);
+
+ return false;
+}
+
+/*
+ * __page_balloon_device - get the balloon device that owns the given page.
+ *
+ * This shall only be used at driver callbacks under proper page lock,
+ * to get access to the balloon device which @page belongs.
+ */
+static inline void *__page_balloon_device(struct page *page)
+{
+ struct address_space *mapping = page->mapping;
+ if (mapping)
+ mapping = mapping->assoc_mapping;
+
+ return mapping;
+}
+
+/*
+ * DEFINE_BALLOON_MAPPING_AOPS - declare and instantiate a callback descriptor
+ * to be used as balloon page->mapping->a_ops.
+ *
+ * @label : declaration identifier (var name)
+ * @isolatepg : callback symbol name for performing the page isolation step
+ * @migratepg : callback symbol name for performing the page migration step
+ * @putbackpg : callback symbol name for performing the page putback step
+ *
+ * address_space_operations utilized 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
+ */
+#define DEFINE_BALLOON_MAPPING_AOPS(label, isolatepg, migratepg, putbackpg) \
+ const struct address_space_operations (label) = { \
+ .migratepage = (migratepg), \
+ .invalidatepage = (isolatepg), \
+ .freepage = (putbackpg), \
+ }
+
+#else
+#define assign_balloon_mapping(p, m) do { } while (0)
+#define clear_balloon_mapping(p) do { } while (0)
+#define free_balloon_mapping(m) do { } while (0)
+#define count_balloon_event(e) do { } while (0)
+#define DEFINE_BALLOON_MAPPING_AOPS(label, isolatepg, migratepg, putbackpg) \
+ const struct {} (label) = {}
+
+static inline bool movable_balloon_page(struct page *page) { return false; }
+static inline bool isolate_balloon_page(struct page *page) { return false; }
+static inline void putback_balloon_page(struct page *page) { return; }
+
+static inline int migrate_balloon_page(struct page *newpage,
+ struct page *page, enum migrate_mode mode)
+{
+ return 0;
+}
+
+static inline gfp_t balloon_mapping_gfp_mask(void)
+{
+ return GFP_HIGHUSER;
+}
+
+static inline void *alloc_balloon_mapping(void *balloon_device,
+ const struct address_space_operations *a_ops)
+{
+ return ERR_PTR(-EOPNOTSUPP);
+}
+#endif /* CONFIG_BALLOON_COMPACTION */
+
+#endif /* _LINUX_BALLOON_COMPACTION_H */
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index e42c762..6df0664 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -24,6 +24,7 @@ enum mapping_flags {
AS_ENOSPC = __GFP_BITS_SHIFT + 1, /* ENOSPC on async write */
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_BALLOON_MAP = __GFP_BITS_SHIFT + 4, /* balloon page special map */
};
static inline void mapping_set_error(struct address_space *mapping, int error)
@@ -53,6 +54,23 @@ static inline int mapping_unevictable(struct address_space
*mapping)
return !!mapping;
}
+static inline void mapping_set_balloon(struct address_space *mapping)
+{
+ set_bit(AS_BALLOON_MAP, &mapping->flags);
+}
+
+static inline void mapping_clear_balloon(struct address_space *mapping)
+{
+ clear_bit(AS_BALLOON_MAP, &mapping->flags);
+}
+
+static inline int mapping_balloon(struct address_space *mapping)
+{
+ if (mapping)
+ return test_bit(AS_BALLOON_MAP, &mapping->flags);
+ return !!mapping;
+}
+
static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
{
return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;
diff --git a/mm/Kconfig b/mm/Kconfig
index d5c8019..0bd783b 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -188,6 +188,21 @@ config SPLIT_PTLOCK_CPUS
default "4"
#
+# support for memory balloon compaction
+config BALLOON_COMPACTION
+ bool "Allow for balloon memory compaction/migration"
+ select COMPACTION
+ depends on VIRTIO_BALLOON
+ help
+ Memory fragmentation introduced by ballooning might reduce
+ significantly the number of 2MB contiguous memory blocks that can be
+ used within a guest, thus imposing performance penalties associated
+ with the reduced number of transparent huge pages that could be used
+ by the guest workload. Allowing the compaction & migration for memory
+ pages enlisted as being part of memory balloon devices avoids the
+ scenario aforementioned and helps improving memory defragmentation.
+
+#
# support for memory compaction
config COMPACTION
bool "Allow for memory compaction"
diff --git a/mm/Makefile b/mm/Makefile
index 92753e2..23e54c5 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -57,3 +57,4 @@ obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o
obj-$(CONFIG_CLEANCACHE) += cleancache.o
obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
+obj-$(CONFIG_BALLOON_COMPACTION) += balloon_compaction.o
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
new file mode 100644
index 0000000..74c09ab
--- /dev/null
+++ b/mm/balloon_compaction.c
@@ -0,0 +1,152 @@
+/*
+ * mm/balloon_compaction.c
+ *
+ * Common interface for making balloon pages movable to compaction.
+ *
+ * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini at
redhat.com>
+ */
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <linux/balloon_compaction.h>
+
+#ifdef CONFIG_BALLOON_COMPACTION
+/*
+ * alloc_balloon_mapping - allocates a special ->mapping for ballooned
pages.
+ * @balloon_device: pointer address that references the balloon device which
+ * owns pages bearing this ->mapping.
+ * @a_ops: balloon_mapping address_space_operations descriptor.
+ *
+ * Users must call it to properly allocate and initialize an instance of
+ * struct address_space which will be used as the special page->mapping for
+ * balloon devices enlisted page instances.
+ */
+struct address_space *alloc_balloon_mapping(void *balloon_device,
+ 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 ->mapping
+ * identification, as well as give a proper hint to the balloon
+ * driver on what GFP allocation mask shall be used.
+ */
+ mapping_set_balloon(mapping);
+ mapping_set_gfp_mask(mapping, balloon_mapping_gfp_mask());
+
+ /* balloon's page->mapping->a_ops callback descriptor */
+ mapping->a_ops = a_ops;
+
+ /*
+ * balloon special page->mapping overloads ->assoc_mapping
+ * to held a reference back to the balloon device wich 'owns'
+ * a given page. This is the way we can cope with multiple
+ * balloon devices without losing reference of several
+ * ballooned pagesets.
+ */
+ mapping->assoc_mapping = balloon_device;
+
+ return mapping;
+}
+EXPORT_SYMBOL_GPL(alloc_balloon_mapping);
+
+static inline void __isolate_balloon_page(struct page *page)
+{
+ page->mapping->a_ops->invalidatepage(page, 0);
+}
+
+static inline void __putback_balloon_page(struct page *page)
+{
+ page->mapping->a_ops->freepage(page);
+}
+
+static inline int __migrate_balloon_page(struct address_space *mapping,
+ struct page *newpage, struct page *page, enum migrate_mode mode)
+{
+ return page->mapping->a_ops->migratepage(mapping, newpage, page,
mode);
+}
+
+/* __isolate_lru_page() counterpart for a ballooned page */
+bool isolate_balloon_page(struct page *page)
+{
+ if (likely(get_page_unless_zero(page))) {
+ /*
+ * As balloon pages are not isolated from LRU lists, concurrent
+ * compaction threads can race against page migration functions
+ * move_to_new_page() & __unmap_and_move().
+ * In order to avoid having an already isolated balloon page
+ * being (wrongly) re-isolated while it is under migration,
+ * lets be sure we have the page lock before proceeding with
+ * the balloon page isolation steps.
+ */
+ 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 by refcount check.
+ */
+ if (__is_movable_balloon_page(page) &&
+ page_count(page) == 2) {
+ __isolate_balloon_page(page);
+ unlock_page(page);
+ return true;
+ }
+ unlock_page(page);
+ }
+ put_page(page);
+ }
+ return false;
+}
+
+/* putback_lru_page() counterpart for a ballooned page */
+void putback_balloon_page(struct page *page)
+{
+ /*
+ * 'lock_page()' stabilizes the page and prevents races against
+ * concurrent isolation threads attempting to re-isolate it.
+ */
+ lock_page(page);
+
+ if (__is_movable_balloon_page(page)) {
+ __putback_balloon_page(page);
+ put_page(page);
+ } else {
+ __WARN();
+ dump_page(page);
+ }
+ unlock_page(page);
+}
+
+/* move_to_new_page() counterpart for a ballooned page */
+int migrate_balloon_page(struct page *newpage,
+ struct page *page, enum migrate_mode mode)
+{
+ struct address_space *mapping;
+ int rc = -EAGAIN;
+
+ BUG_ON(!trylock_page(newpage));
+
+ if (WARN_ON(!__is_movable_balloon_page(page))) {
+ dump_page(page);
+ unlock_page(newpage);
+ return rc;
+ }
+
+ mapping = page->mapping;
+ if (mapping)
+ rc = __migrate_balloon_page(mapping, newpage, page, mode);
+
+ unlock_page(newpage);
+ return rc;
+}
+#endif /* CONFIG_BALLOON_COMPACTION */
--
1.7.11.4
Rafael Aquini
2012-Sep-17 16:38 UTC
[PATCH v10 2/5] mm: introduce compaction and migration for ballooned pages
Memory fragmentation introduced by ballooning might reduce significantly
the number of 2MB contiguous memory blocks that can be used within a guest,
thus imposing performance penalties associated with the reduced number of
transparent huge pages that could be used by the guest workload.
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 at redhat.com>
---
mm/compaction.c | 47 ++++++++++++++++++++++++++++-------------------
mm/migrate.c | 36 ++++++++++++++++++++++++++++++++++--
2 files changed, 62 insertions(+), 21 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 7fcd3a5..e50836b 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/balloon_compaction.h>
#include "internal.h"
#if defined CONFIG_COMPACTION || defined CONFIG_CMA
@@ -358,32 +359,40 @@ 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 (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 (unlikely(movable_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++;
diff --git a/mm/migrate.c b/mm/migrate.c
index 77ed2d7..ec439f8 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -35,6 +35,7 @@
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>
#include <linux/gfp.h>
+#include <linux/balloon_compaction.h>
#include <asm/tlbflush.h>
@@ -79,7 +80,10 @@ 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(movable_balloon_page(page)))
+ putback_balloon_page(page);
+ else
+ putback_lru_page(page);
}
}
@@ -799,6 +803,18 @@ static int __unmap_and_move(struct page *page, struct page
*newpage,
goto skip_unmap;
}
+ if (unlikely(movable_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 = migrate_balloon_page(newpage, page, mode);
+ goto uncharge;
+ }
+
/* Establish migration ptes or remove ptes */
try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
@@ -814,7 +830,8 @@ skip_unmap:
put_anon_vma(anon_vma);
uncharge:
- mem_cgroup_end_migration(mem, page, newpage, rc == 0);
+ mem_cgroup_end_migration(mem, page, newpage,
+ (rc == 0 || rc == BALLOON_MIGRATION_RETURN));
unlock:
unlock_page(page);
out:
@@ -846,6 +863,21 @@ 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 (unlikely(rc == BALLOON_MIGRATION_RETURN)) {
+ /*
+ * A ballooned page has been migrated already.
+ * Now, it's the time to remove the old page from the isolated
+ * pageset list and handle it back to Buddy, wrap-up counters
+ * and return.
+ */
+ dec_zone_page_state(page, NR_ISOLATED_ANON +
+ page_is_file_cache(page));
+ list_del(&page->lru);
+ put_page(page);
+ __free_page(page);
+ return 0;
+ }
out:
if (rc != -EAGAIN) {
/*
--
1.7.11.4
Rafael Aquini
2012-Sep-17 16:38 UTC
[PATCH v10 3/5] virtio_balloon: introduce migration primitives to balloon pages
Memory fragmentation introduced by ballooning might reduce significantly
the number of 2MB contiguous memory blocks that can be used within a guest,
thus imposing performance penalties associated with the reduced number of
transparent huge pages that could be used by the guest workload.
Besides making balloon pages movable at allocation time and introducing
the necessary primitives to perform balloon page migration/compaction,
this patch also introduces the following locking scheme, in order to
enhance the syncronization methods for accessing elements of struct
virtio_balloon, thus providing protection against concurrent access
introduced by parallel memory compaction threads.
- balloon_lock (mutex) : synchronizes the access demand to elements of
struct virtio_balloon and its queue operations;
- pages_lock (spinlock): special protection to balloon's pages bookmarking
elements (list and atomic counters) against the
potential memory compaction concurrency;
Signed-off-by: Rafael Aquini <aquini at redhat.com>
---
drivers/virtio/virtio_balloon.c | 305 +++++++++++++++++++++++++++++++++++++---
1 file changed, 286 insertions(+), 19 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 0908e60..a52c768 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -27,6 +27,7 @@
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/module.h>
+#include <linux/balloon_compaction.h>
/*
* Balloon device works in 4K page units. So each page is pointed to by
@@ -34,6 +35,7 @@
* page units.
*/
#define VIRTIO_BALLOON_PAGES_PER_PAGE (PAGE_SIZE >>
VIRTIO_BALLOON_PFN_SHIFT)
+#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
struct virtio_balloon
{
@@ -46,11 +48,24 @@ struct virtio_balloon
/* The thread servicing the balloon. */
struct task_struct *thread;
+ /* balloon special page->mapping */
+ struct address_space *mapping;
+
+ /* Synchronize access/update to this struct virtio_balloon elements */
+ struct mutex balloon_lock;
+
/* Waiting for host to ack the pages we released. */
wait_queue_head_t acked;
+ /* Protect pages list, and pages bookeeping counters */
+ spinlock_t pages_lock;
+
+ /* Number of balloon pages isolated from 'pages' list for compaction
*/
+ unsigned int num_isolated_pages;
+
/* Number of balloon pages we've told the Host we're not using. */
unsigned int num_pages;
+
/*
* The pages we've told the Host we're not using.
* Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
@@ -60,7 +75,7 @@ struct virtio_balloon
/* The array of pfns we tell the Host about. */
unsigned int num_pfns;
- u32 pfns[256];
+ u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
/* Memory statistics */
int need_stats_update;
@@ -122,13 +137,17 @@ static void set_page_pfns(u32 pfns[], struct page *page)
static void fill_balloon(struct virtio_balloon *vb, size_t num)
{
+ /* Get the proper GFP alloc mask from vb->mapping flags */
+ gfp_t vb_gfp_mask = mapping_gfp_mask(vb->mapping);
+
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
+ mutex_lock(&vb->balloon_lock);
for (vb->num_pfns = 0; vb->num_pfns < num;
vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
- struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
- __GFP_NOMEMALLOC | __GFP_NOWARN);
+ struct page *page = alloc_page(vb_gfp_mask | __GFP_NORETRY |
+ __GFP_NOWARN | __GFP_NOMEMALLOC);
if (!page) {
if (printk_ratelimit())
dev_printk(KERN_INFO, &vb->vdev->dev,
@@ -139,9 +158,15 @@ static void fill_balloon(struct virtio_balloon *vb, size_t
num)
break;
}
set_page_pfns(vb->pfns + vb->num_pfns, page);
- vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
totalram_pages--;
+
+ BUG_ON(!trylock_page(page));
+ spin_lock(&vb->pages_lock);
list_add(&page->lru, &vb->pages);
+ assign_balloon_mapping(page, vb->mapping);
+ vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
+ spin_unlock(&vb->pages_lock);
+ unlock_page(page);
}
/* Didn't get any? Oh well. */
@@ -149,6 +174,7 @@ static void fill_balloon(struct virtio_balloon *vb, size_t
num)
return;
tell_host(vb, vb->inflate_vq);
+ mutex_unlock(&vb->balloon_lock);
}
static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
@@ -162,19 +188,64 @@ static void release_pages_by_pfn(const u32 pfns[],
unsigned int num)
}
}
-static void leak_balloon(struct virtio_balloon *vb, size_t num)
+/*
+ * __leak_balloon - back-end for the balloon pages deflate mechanism.
+ * @vb : pointer to the balloon device descriptor we're leaking (deflating)
+ * @leak_target : how many pages we are looking to drain off balloon's
list.
+ *
+ * Here we do all the heavy lifting on behalf of leak_balloon(). This function
+ * must only be called by leak_balloon(), embedded on its wait_event() callsite
+ * and under the following locking scheme:
+ * mutex(balloon_lock)
+ * +--spinlock(pages_lock)
+ * +--__leak_balloon
+ */
+static int __leak_balloon(struct virtio_balloon *vb, size_t leak_target)
{
- struct page *page;
-
/* We can only do one array worth at a time. */
- num = min(num, ARRAY_SIZE(vb->pfns));
+ leak_target = min(leak_target, ARRAY_SIZE(vb->pfns));
- for (vb->num_pfns = 0; vb->num_pfns < num;
+ for (vb->num_pfns = 0; vb->num_pfns < leak_target;
vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
- page = list_first_entry(&vb->pages, struct page, lru);
+ struct page *page = NULL;
+ /*
+ * leak_balloon() attempts to work releasing balloon pages by
+ * groups of (at most) 'VIRTIO_BALLOON_ARRAY_PFNS_MAX' size
+ * at each round.
+ * When compaction isolates pages from balloon page list,
+ * we might end up finding less pages on balloon's list than
+ * what is our desired 'leak_target'.
+ * When such occurrence happens, however, whe shall wrap-up
+ * the work for this round and wait until enough pages get
+ * inserted back into balloon's page list before proceeding.
+ */
+ if (!list_empty(&vb->pages))
+ page = list_first_entry(&vb->pages, struct page, lru);
+
+ if (!page)
+ break;
+
+ /*
+ * Grab the page lock to avoid racing against threads isolating
+ * pages from, or migrating pages back to vb->pages list.
+ * (both tasks are done under page lock protection)
+ *
+ * Failing to grab the page lock here means this page is being
+ * isolated already, or its migration has not finished yet.
+ *
+ * We simply cannot afford to keep waiting on page lock here,
+ * otherwise we might cause a lock inversion and remain dead-
+ * locked with threads isolating/migrating pages.
+ * So, we give up this round if we fail to grab the page lock.
+ */
+ if (!trylock_page(page))
+ break;
+
+ clear_balloon_mapping(page);
list_del(&page->lru);
- set_page_pfns(vb->pfns + vb->num_pfns, page);
vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
+ set_page_pfns(vb->pfns + vb->num_pfns, page);
+ unlock_page(page);
}
/*
@@ -182,8 +253,58 @@ static void leak_balloon(struct virtio_balloon *vb, size_t
num)
* virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
* is true, we *have* to do it in this order
*/
- tell_host(vb, vb->deflate_vq);
- release_pages_by_pfn(vb->pfns, vb->num_pfns);
+ if (vb->num_pfns > 0) {
+ spin_unlock(&vb->pages_lock);
+ tell_host(vb, vb->deflate_vq);
+ release_pages_by_pfn(vb->pfns, vb->num_pfns);
+ spin_lock(&vb->pages_lock);
+ }
+
+ return vb->num_pfns;
+}
+
+/*
+ * __wait_on_isolate_pages - evaluates the condition that breaks leak_balloon()
+ * wait_event loop.
+ * @vb : pointer to the balloon device descriptor we're leaking (deflating)
+ * @leak_target : pointer to our leak target.
+ *
+ * This is a helper to leak_balloon() wait_event scheme. Here we test the
+ * conditions to break the wait loop, as well as we embed the call to
+ * __leak_balloon() under the proper locking scheme.
+ */
+static inline bool __wait_on_isolated_pages(struct virtio_balloon *vb,
+ size_t *leak_target)
+{
+ bool cond = false;
+ size_t leaked = 0;
+
+ mutex_lock(&vb->balloon_lock);
+ spin_lock(&vb->pages_lock);
+ if (*leak_target <= (vb->num_pages - vb->num_isolated_pages))
+ leaked = __leak_balloon(vb, *leak_target);
+
+ /* compensate the target with the amount of pages leaked this round */
+ *leak_target -= leaked;
+ cond = (*leak_target <= (vb->num_pages - vb->num_isolated_pages));
+ spin_unlock(&vb->pages_lock);
+ mutex_unlock(&vb->balloon_lock);
+ return cond;
+}
+
+/*
+ * leak_balloon - front-end for balloon pages deflate mechanism.
+ * @vb : pointer to the balloon device descriptor we're leaking (deflating)
+ * @leak_target : how many pages we are looking to drain off balloon's
list.
+ */
+static void leak_balloon(struct virtio_balloon *vb, size_t leak_target)
+{
+ /* We can only do one array worth at a time. */
+ leak_target = min(leak_target, ARRAY_SIZE(vb->pfns));
+
+ /* Deflate balloon, or wait if there are too much isolated pages */
+ wait_event(vb->config_change,
+ __wait_on_isolated_pages(vb, &leak_target));
}
static inline void update_stat(struct virtio_balloon *vb, int idx,
@@ -239,6 +360,7 @@ static void stats_handle_request(struct virtio_balloon *vb)
struct scatterlist sg;
unsigned int len;
+ mutex_lock(&vb->balloon_lock);
vb->need_stats_update = 0;
update_balloon_stats(vb);
@@ -249,6 +371,7 @@ static void stats_handle_request(struct virtio_balloon *vb)
if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
BUG();
virtqueue_kick(vq);
+ mutex_unlock(&vb->balloon_lock);
}
static void virtballoon_changed(struct virtio_device *vdev)
@@ -261,22 +384,29 @@ static void virtballoon_changed(struct virtio_device
*vdev)
static inline s64 towards_target(struct virtio_balloon *vb)
{
__le32 v;
- s64 target;
+ s64 target, actual;
+ spin_lock(&vb->pages_lock);
+ actual = vb->num_pages;
vb->vdev->config->get(vb->vdev,
offsetof(struct virtio_balloon_config, num_pages),
&v, sizeof(v));
target = le32_to_cpu(v);
- return target - vb->num_pages;
+ spin_unlock(&vb->pages_lock);
+ return target - actual;
}
static void update_balloon_size(struct virtio_balloon *vb)
{
- __le32 actual = cpu_to_le32(vb->num_pages);
+ __le32 actual;
+
+ spin_lock(&vb->pages_lock);
+ actual = cpu_to_le32(vb->num_pages);
vb->vdev->config->set(vb->vdev,
offsetof(struct virtio_balloon_config, actual),
&actual, sizeof(actual));
+ spin_unlock(&vb->pages_lock);
}
static int balloon(void *_vballoon)
@@ -339,9 +469,121 @@ static int init_vqs(struct virtio_balloon *vb)
return 0;
}
+#ifdef CONFIG_BALLOON_COMPACTION
+/*
+ * virtballoon_isolatepage - perform the balloon page isolation on behalf of
+ * a compation thread. (called under page lock)
+ * @page: the page to isolated from balloon's page list.
+ * @mode: not used for balloon page isolation.
+ *
+ * A memory compaction thread works by isolating pages from private lists,
+ * like LRUs or the balloon's page list (here), to a privative pageset that
+ * will be migrated subsequently. After the mentioned pageset gets isolated
+ * compaction relies on page migration procedures to do the heavy lifting.
+ *
+ * This function isolates a page from the balloon private page list.
+ * Called through balloon_mapping->a_ops.
+ */
+void virtballoon_isolatepage(struct page *page, unsigned long mode)
+{
+ struct virtio_balloon *vb = __page_balloon_device(page);
+
+ BUG_ON(!vb);
+
+ spin_lock(&vb->pages_lock);
+ list_del(&page->lru);
+ vb->num_isolated_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
+ spin_unlock(&vb->pages_lock);
+}
+
+/*
+ * virtballoon_migratepage - perform the balloon page migration on behalf of
+ * a compation thread. (called under page lock)
+ * @mapping: the page->mapping which will be assigned to the new migrated
page.
+ * @newpage: page that will replace the isolated page after migration finishes.
+ * @page : the isolated (old) page that is about to be migrated to newpage.
+ * @mode : compaction mode -- not used for balloon page migration.
+ *
+ * After a ballooned page gets isolated by compaction procedures, this is the
+ * function that performs the page migration on behalf of a compaction thread
+ * The page migration for virtio balloon is done in a simple swap fashion which
+ * follows these two macro steps:
+ * 1) insert newpage into vb->pages list and update the host about it;
+ * 2) update the host about the old page removed from vb->pages list;
+ *
+ * This function preforms the balloon page migration task.
+ * Called through balloon_mapping->a_ops.
+ */
+int virtballoon_migratepage(struct address_space *mapping,
+ struct page *newpage, struct page *page, enum migrate_mode mode)
+{
+ struct virtio_balloon *vb = __page_balloon_device(page);
+
+ BUG_ON(!vb);
+
+ mutex_lock(&vb->balloon_lock);
+
+ /* balloon's page migration 1st step */
+ vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
+ spin_lock(&vb->pages_lock);
+ list_add(&newpage->lru, &vb->pages);
+ assign_balloon_mapping(newpage, mapping);
+ vb->num_isolated_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
+ spin_unlock(&vb->pages_lock);
+ set_page_pfns(vb->pfns, newpage);
+ tell_host(vb, vb->inflate_vq);
+
+ /* balloon's page migration 2nd step */
+ vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
+ clear_balloon_mapping(page);
+ set_page_pfns(vb->pfns, page);
+ tell_host(vb, vb->deflate_vq);
+
+ mutex_unlock(&vb->balloon_lock);
+ wake_up(&vb->config_change);
+
+ return BALLOON_MIGRATION_RETURN;
+}
+
+/*
+ * virtballoon_putbackpage - insert an isolated page back into the list it was
+ * once taken off by a compaction thread.
+ * (called under page lock)
+ * @page: page that will be re-inserted into balloon page list.
+ *
+ * If for some reason, a compaction thread can not finish all its job in one
+ * round, and some isolated pages are still remaining at compaction's
thread
+ * privative pageset (waiting for migration), then those pages will get
+ * re-inserted into their balloon private lists before compaction thread ends.
+ *
+ * This function inserts an isolated but not migrated balloon page
+ * back into private balloon list.
+ * Called through balloon_mapping->a_ops.
+ */
+void virtballoon_putbackpage(struct page *page)
+{
+ struct virtio_balloon *vb = __page_balloon_device(page);
+
+ BUG_ON(!vb);
+
+ spin_lock(&vb->pages_lock);
+ list_add(&page->lru, &vb->pages);
+ vb->num_isolated_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
+ spin_unlock(&vb->pages_lock);
+ wake_up(&vb->config_change);
+}
+#endif /* CONFIG_BALLOON_COMPACTION */
+
+/* define the balloon_mapping->a_ops callbacks to allow compaction/migration
*/
+static DEFINE_BALLOON_MAPPING_AOPS(virtio_balloon_aops,
+ virtballoon_isolatepage,
+ virtballoon_migratepage,
+ virtballoon_putbackpage);
+
static int virtballoon_probe(struct virtio_device *vdev)
{
struct virtio_balloon *vb;
+ struct address_space *vb_mapping;
int err;
vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
@@ -351,12 +593,25 @@ static int virtballoon_probe(struct virtio_device *vdev)
}
INIT_LIST_HEAD(&vb->pages);
+ mutex_init(&vb->balloon_lock);
+ spin_lock_init(&vb->pages_lock);
+
vb->num_pages = 0;
+ vb->num_isolated_pages = 0;
init_waitqueue_head(&vb->config_change);
init_waitqueue_head(&vb->acked);
vb->vdev = vdev;
vb->need_stats_update = 0;
+ vb_mapping = alloc_balloon_mapping(vb, &virtio_balloon_aops);
+ if (IS_ERR(vb_mapping)) {
+ err = PTR_ERR(vb_mapping);
+ if (err != -EOPNOTSUPP)
+ goto out_free_vb;
+ }
+
+ vb->mapping = vb_mapping;
+
err = init_vqs(vb);
if (err)
goto out_free_vb;
@@ -372,16 +627,28 @@ static int virtballoon_probe(struct virtio_device *vdev)
out_del_vqs:
vdev->config->del_vqs(vdev);
out_free_vb:
+ free_balloon_mapping(vb_mapping);
kfree(vb);
out:
return err;
}
+static inline size_t __get_num_pages(struct virtio_balloon *vb)
+{
+ size_t num_pages;
+ spin_lock(&vb->pages_lock);
+ num_pages = vb->num_pages;
+ spin_unlock(&vb->pages_lock);
+ return num_pages;
+}
+
static void remove_common(struct virtio_balloon *vb)
{
+ size_t num_pages;
/* There might be pages left in the balloon: free them. */
- while (vb->num_pages)
- leak_balloon(vb, vb->num_pages);
+ while ((num_pages = __get_num_pages(vb)) > 0)
+ leak_balloon(vb, num_pages);
+
update_balloon_size(vb);
/* Now we reset the device so we can clean up the queues. */
@@ -396,6 +663,7 @@ static void __devexit virtballoon_remove(struct
virtio_device *vdev)
kthread_stop(vb->thread);
remove_common(vb);
+ free_balloon_mapping(vb->mapping);
kfree(vb);
}
@@ -408,7 +676,6 @@ static int virtballoon_freeze(struct virtio_device *vdev)
* The kthread is already frozen by the PM core before this
* function is called.
*/
-
remove_common(vb);
return 0;
}
--
1.7.11.4
The PATCH "mm: introduce compaction and migration for virtio ballooned
pages"
hacks around putback_lru_pages() in order to allow ballooned pages to be
re-inserted on balloon page list as if a ballooned page was like a LRU page.
As ballooned pages are not legitimate LRU pages, this patch introduces
putback_movable_pages() to properly cope with cases where the isolated
pageset contains ballooned pages and LRU pages, thus fixing the mentioned
inelegant hack around putback_lru_pages().
Signed-off-by: Rafael Aquini <aquini at redhat.com>
---
include/linux/migrate.h | 2 ++
mm/compaction.c | 4 ++--
mm/migrate.c | 20 ++++++++++++++++++++
mm/page_alloc.c | 2 +-
4 files changed, 25 insertions(+), 3 deletions(-)
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index ce7e667..ff103a1 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -10,6 +10,7 @@ typedef struct page *new_page_t(struct page *, unsigned long
private, int **);
#ifdef CONFIG_MIGRATION
extern void putback_lru_pages(struct list_head *l);
+extern void putback_movable_pages(struct list_head *l);
extern int migrate_page(struct address_space *,
struct page *, struct page *, enum migrate_mode);
extern int migrate_pages(struct list_head *l, new_page_t x,
@@ -33,6 +34,7 @@ extern int migrate_huge_page_move_mapping(struct address_space
*mapping,
#else
static inline void putback_lru_pages(struct list_head *l) {}
+static inline void putback_movable_pages(struct list_head *l) {}
static inline int migrate_pages(struct list_head *l, new_page_t x,
unsigned long private, bool offlining,
enum migrate_mode mode) { return -ENOSYS; }
diff --git a/mm/compaction.c b/mm/compaction.c
index e50836b..409b2f5 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -817,9 +817,9 @@ static int compact_zone(struct zone *zone, struct
compact_control *cc)
trace_mm_compaction_migratepages(nr_migrate - nr_remaining,
nr_remaining);
- /* Release LRU pages not migrated */
+ /* Release isolated pages not migrated */
if (err) {
- putback_lru_pages(&cc->migratepages);
+ putback_movable_pages(&cc->migratepages);
cc->nr_migratepages = 0;
if (err == -ENOMEM) {
ret = COMPACT_PARTIAL;
diff --git a/mm/migrate.c b/mm/migrate.c
index ec439f8..e47daf5 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -80,6 +80,26 @@ 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);
+ }
+}
+
+/*
+ * Put previously isolated pages back onto the appropriate lists
+ * from where they were once taken off for compaction/migration.
+ *
+ * This function shall be used instead of putback_lru_pages(),
+ * whenever the isolated pageset has been built by isolate_migratepages_range()
+ */
+void putback_movable_pages(struct list_head *l)
+{
+ struct page *page;
+ struct page *page2;
+
+ list_for_each_entry_safe(page, page2, l, lru) {
+ list_del(&page->lru);
+ dec_zone_page_state(page, NR_ISOLATED_ANON +
+ page_is_file_cache(page));
if (unlikely(movable_balloon_page(page)))
putback_balloon_page(page);
else
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c66fb87..a0c2cc5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5675,7 +5675,7 @@ static int __alloc_contig_migrate_range(unsigned long
start, unsigned long end)
0, false, MIGRATE_SYNC);
}
- putback_lru_pages(&cc.migratepages);
+ putback_movable_pages(&cc.migratepages);
return ret > 0 ? 0 : ret;
}
--
1.7.11.4
Rafael Aquini
2012-Sep-17 16:38 UTC
[PATCH v10 5/5] mm: add vm event counters for balloon pages compaction
This patch introduces a new set of vm event counters to keep track of
ballooned pages compaction activity.
Signed-off-by: Rafael Aquini <aquini at redhat.com>
---
drivers/virtio/virtio_balloon.c | 1 +
include/linux/vm_event_item.h | 8 +++++++-
mm/balloon_compaction.c | 2 ++
mm/migrate.c | 1 +
mm/vmstat.c | 10 +++++++++-
5 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index a52c768..c57d1ed 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -541,6 +541,7 @@ int virtballoon_migratepage(struct address_space *mapping,
mutex_unlock(&vb->balloon_lock);
wake_up(&vb->config_change);
+ count_balloon_event(COMPACTBALLOONMIGRATED);
return BALLOON_MIGRATION_RETURN;
}
diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 57f7b10..13573fe 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -41,7 +41,13 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
#ifdef CONFIG_COMPACTION
COMPACTBLOCKS, COMPACTPAGES, COMPACTPAGEFAILED,
COMPACTSTALL, COMPACTFAIL, COMPACTSUCCESS,
-#endif
+#ifdef CONFIG_BALLOON_COMPACTION
+ COMPACTBALLOONISOLATED, /* isolated from balloon pagelist */
+ COMPACTBALLOONMIGRATED, /* balloon page sucessfully migrated */
+ COMPACTBALLOONRELEASED, /* old-page released after migration */
+ COMPACTBALLOONRETURNED, /* putback to pagelist, not-migrated */
+#endif /* CONFIG_BALLOON_COMPACTION */
+#endif /* CONFIG_COMPACTION */
#ifdef CONFIG_HUGETLB_PAGE
HTLB_BUDDY_PGALLOC, HTLB_BUDDY_PGALLOC_FAIL,
#endif
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index 74c09ab..873af56 100644
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -98,6 +98,7 @@ bool isolate_balloon_page(struct page *page)
if (__is_movable_balloon_page(page) &&
page_count(page) == 2) {
__isolate_balloon_page(page);
+ count_balloon_event(COMPACTBALLOONISOLATED);
unlock_page(page);
return true;
}
@@ -120,6 +121,7 @@ void putback_balloon_page(struct page *page)
if (__is_movable_balloon_page(page)) {
__putback_balloon_page(page);
put_page(page);
+ count_balloon_event(COMPACTBALLOONRETURNED);
} else {
__WARN();
dump_page(page);
diff --git a/mm/migrate.c b/mm/migrate.c
index e47daf5..124b16b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -896,6 +896,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned
long private,
list_del(&page->lru);
put_page(page);
__free_page(page);
+ count_balloon_event(COMPACTBALLOONRELEASED);
return 0;
}
out:
diff --git a/mm/vmstat.c b/mm/vmstat.c
index df7a674..5824ad2 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -768,7 +768,15 @@ const char * const vmstat_text[] = {
"compact_stall",
"compact_fail",
"compact_success",
-#endif
+
+#ifdef CONFIG_BALLOON_COMPACTION
+ "compact_balloon_isolated",
+ "compact_balloon_migrated",
+ "compact_balloon_released",
+ "compact_balloon_returned",
+#endif /* CONFIG_BALLOON_COMPACTION */
+
+#endif /* CONFIG_COMPACTION */
#ifdef CONFIG_HUGETLB_PAGE
"htlb_buddy_alloc_success",
--
1.7.11.4
Andrew Morton
2012-Sep-17 22:15 UTC
[PATCH v10 0/5] make balloon pages movable by compaction
On Mon, 17 Sep 2012 13:38:15 -0300 Rafael Aquini <aquini at redhat.com> wrote:> Memory fragmentation introduced by ballooning might reduce significantly > the number of 2MB contiguous memory blocks that can be used within a guest, > thus imposing performance penalties associated with the reduced number of > transparent huge pages that could be used by the guest workload. > > This patch-set follows the main idea discussed at 2012 LSFMMS session: > "Ballooning for transparent huge pages" -- http://lwn.net/Articles/490114/ > to introduce the required changes to the virtio_balloon driver, as well as > the changes to the core compaction & migration bits, in order to make those > subsystems aware of ballooned pages and allow memory balloon pages become > movable within a guest, thus avoiding the aforementioned fragmentation issue > > Following are numbers that prove this patch benefits on allowing compaction > to be more effective at memory ballooned guests. > > Results for STRESS-HIGHALLOC benchmark, from Mel Gorman's mmtests suite, > running on a 4gB RAM KVM guest which was ballooning 1gB RAM in 256mB chunks, > at every minute (inflating/deflating), while test was running:How can a patchset reach v10 and have zero Reviewed-by's? The patchset looks reasonable to me and your empirical results look good. But I don't feel that I'm in a position to decide on its overall desirability, either in a standalone sense or in comparison to any alternative schemes which anyone has proposed. IOW, Rusty and KVM folks: please consider thyself poked. I looked through the code and have some comments which are minor in the overall scheme of things. I'll be more comfortable when a compaction expert has had a go over it. IOW, Mel joins the pokee list ;) (The question of "overall desirability" is the big one here. Do we actually want to add this to Linux? The rest is details which we can work out).
Peter Zijlstra
2012-Sep-24 12:44 UTC
[PATCH v10 1/5] mm: introduce a common interface for balloon pages mobility
On Mon, 2012-09-17 at 13:38 -0300, Rafael Aquini wrote:> +static inline void assign_balloon_mapping(struct page *page, > + struct address_space > *mapping) > +{ > + page->mapping = mapping; > + smp_wmb(); > +} > + > +static inline void clear_balloon_mapping(struct page *page) > +{ > + page->mapping = NULL; > + smp_wmb(); > +}barriers without a comment describing the data race are a mortal sin.
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