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* [PATCH v4 0/6] mm / virtio: Provide support for unused page reporting
@ 2019-08-07 22:41 Alexander Duyck
  2019-08-07 22:41 ` [PATCH v4 1/6] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
                   ` (8 more replies)
  0 siblings, 9 replies; 17+ messages in thread
From: Alexander Duyck @ 2019-08-07 22:41 UTC (permalink / raw)
  To: nitesh, kvm, david, mst, dave.hansen, linux-kernel, linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck

This series provides an asynchronous means of reporting to a hypervisor
that a guest page is no longer in use and can have the data associated
with it dropped. To do this I have implemented functionality that allows
for what I am referring to as unused page reporting

The functionality for this is fairly simple. When enabled it will allocate
statistics to track the number of reported pages in a given free area.
When the number of free pages exceeds this value plus a high water value,
currently 32, it will begin performing page reporting which consists of
pulling pages off of free list and placing them into a scatter list. The
scatterlist is then given to the page reporting device and it will perform
the required action to make the pages "reported", in the case of
virtio-balloon this results in the pages being madvised as MADV_DONTNEED
and as such they are forced out of the guest. After this they are placed
back on the free list, and an additional bit is added if they are not
merged indicating that they are a reported buddy page instead of a
standard buddy page. The cycle then repeats with additional non-reported
pages being pulled until the free areas all consist of reported pages.

I am leaving a number of things hard-coded such as limiting the lowest
order processed to PAGEBLOCK_ORDER, and have left it up to the guest to
determine what the limit is on how many pages it wants to allocate to
process the hints. The upper limit for this is based on the size of the
queue used to store the scattergather list.

My primary testing has just been to verify the memory is being freed after
allocation by running memhog 40g on a 40g guest and watching the total
free memory via /proc/meminfo on the host. With this I have verified most
of the memory is freed after each iteration. As far as performance I have
been mainly focusing on the will-it-scale/page_fault1 test running with
16 vcpus. I have modified it to use Transparent Huge Pages. With this I
see almost no difference, -0.08%, with the patches applied and the feature
disabled. I see a regression of -0.86% with the feature enabled, but the
madvise disabled in the hypervisor due to a device being assigned. With
the feature fully enabled I see a regression of -3.27% versus the baseline
without these patches applied. In my testing I found that most of the
overhead was due to the page zeroing that comes as a result of the pages
having to be faulted back into the guest.

One side effect of these patches is that the guest becomes much more
resilient in terms of NUMA locality. With the pages being freed and then
reallocated when used it allows for the pages to be much closer to the
active thread, and as a result there can be situations where this patch
set will out-perform the stock kernel when the guest memory is not local
to the guest vCPUs. To avoid that in my testing I set the affinity of all
the vCPUs and QEMU instance to the same node.

Changes from the RFC:
https://lore.kernel.org/lkml/20190530215223.13974.22445.stgit@localhost.localdomain/
Moved aeration requested flag out of aerator and into zone->flags.
Moved boundary out of free_area and into local variables for aeration.
Moved aeration cycle out of interrupt and into workqueue.
Left nr_free as total pages instead of splitting it between raw and aerated.
Combined size and physical address values in virtio ring into one 64b value.

Changes from v1:
https://lore.kernel.org/lkml/20190619222922.1231.27432.stgit@localhost.localdomain/
Dropped "waste page treatment" in favor of "page hinting"
Renamed files and functions from "aeration" to "page_hinting"
Moved from page->lru list to scatterlist
Replaced wait on refcnt in shutdown with RCU and cancel_delayed_work_sync
Virtio now uses scatterlist directly instead of intermediate array
Moved stats out of free_area, now in separate area and pointed to from zone
Merged patch 5 into patch 4 to improve review-ability
Updated various code comments throughout

Changes from v2:
https://lore.kernel.org/lkml/20190724165158.6685.87228.stgit@localhost.localdomain/
Dropped "page hinting" in favor of "page reporting"
Renamed files from "hinting" to "reporting"
Replaced "Hinted" page type with "Reported" page flag
Added support for page poisoning while hinting is active
Add QEMU patch that implements PAGE_POISON feature

Changes from v3:
https://lore.kernel.org/lkml/20190801222158.22190.96964.stgit@localhost.localdomain/
Added mutex lock around page reporting startup and shutdown
Fixed reference to "page aeration" in patch 2
Split page reporting function bit out into separate QEMU patch
Limited capacity of scatterlist to vq size - 1 instead of vq size
Added exception handling for case of virtio descriptor allocation failure

---

Alexander Duyck (6):
      mm: Adjust shuffle code to allow for future coalescing
      mm: Move set/get_pcppage_migratetype to mmzone.h
      mm: Use zone and order instead of free area in free_list manipulators
      mm: Introduce Reported pages
      virtio-balloon: Pull page poisoning config out of free page hinting
      virtio-balloon: Add support for providing unused page reports to host


 drivers/virtio/Kconfig              |    1 
 drivers/virtio/virtio_balloon.c     |   84 +++++++++
 include/linux/mmzone.h              |  116 ++++++++-----
 include/linux/page-flags.h          |   11 +
 include/linux/page_reporting.h      |  138 +++++++++++++++
 include/uapi/linux/virtio_balloon.h |    1 
 mm/Kconfig                          |    5 +
 mm/Makefile                         |    1 
 mm/internal.h                       |   18 ++
 mm/memory_hotplug.c                 |    1 
 mm/page_alloc.c                     |  238 +++++++++++++++++++--------
 mm/page_reporting.c                 |  313 +++++++++++++++++++++++++++++++++++
 mm/shuffle.c                        |   24 ---
 mm/shuffle.h                        |   32 ++++
 14 files changed, 844 insertions(+), 139 deletions(-)
 create mode 100644 include/linux/page_reporting.h
 create mode 100644 mm/page_reporting.c

--

^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v4 1/6] mm: Adjust shuffle code to allow for future coalescing
  2019-08-07 22:41 [PATCH v4 0/6] mm / virtio: Provide support for unused page reporting Alexander Duyck
@ 2019-08-07 22:41 ` Alexander Duyck
  2019-08-07 22:41 ` [PATCH v4 2/6] mm: Move set/get_pcppage_migratetype to mmzone.h Alexander Duyck
                   ` (7 subsequent siblings)
  8 siblings, 0 replies; 17+ messages in thread
From: Alexander Duyck @ 2019-08-07 22:41 UTC (permalink / raw)
  To: nitesh, kvm, david, mst, dave.hansen, linux-kernel, linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

This patch is meant to move the head/tail adding logic out of the shuffle
code and into the __free_one_page function since ultimately that is where
it is really needed anyway. By doing this we should be able to reduce the
overhead and can consolidate all of the list addition bits in one spot.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 include/linux/mmzone.h |   12 --------
 mm/page_alloc.c        |   70 +++++++++++++++++++++++++++---------------------
 mm/shuffle.c           |   24 ----------------
 mm/shuffle.h           |   32 ++++++++++++++++++++++
 4 files changed, 71 insertions(+), 67 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index aa0dd8ca36c8..c6bd8e9bb476 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -116,18 +116,6 @@ static inline void add_to_free_area_tail(struct page *page, struct free_area *ar
 	area->nr_free++;
 }
 
-#ifdef CONFIG_SHUFFLE_PAGE_ALLOCATOR
-/* Used to preserve page allocation order entropy */
-void add_to_free_area_random(struct page *page, struct free_area *area,
-		int migratetype);
-#else
-static inline void add_to_free_area_random(struct page *page,
-		struct free_area *area, int migratetype)
-{
-	add_to_free_area(page, area, migratetype);
-}
-#endif
-
 /* Used for pages which are on another list */
 static inline void move_to_free_area(struct page *page, struct free_area *area,
 			     int migratetype)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index af29c05e23aa..e3cb6e7aa296 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -877,6 +877,36 @@ static inline struct capture_control *task_capc(struct zone *zone)
 #endif /* CONFIG_COMPACTION */
 
 /*
+ * If this is not the largest possible page, check if the buddy
+ * of the next-highest order is free. If it is, it's possible
+ * that pages are being freed that will coalesce soon. In case,
+ * that is happening, add the free page to the tail of the list
+ * so it's less likely to be used soon and more likely to be merged
+ * as a higher order page
+ */
+static inline bool
+buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,
+		   struct page *page, unsigned int order)
+{
+	struct page *higher_page, *higher_buddy;
+	unsigned long combined_pfn;
+
+	if (order >= MAX_ORDER - 2)
+		return false;
+
+	if (!pfn_valid_within(buddy_pfn))
+		return false;
+
+	combined_pfn = buddy_pfn & pfn;
+	higher_page = page + (combined_pfn - pfn);
+	buddy_pfn = __find_buddy_pfn(combined_pfn, order + 1);
+	higher_buddy = higher_page + (buddy_pfn - combined_pfn);
+
+	return pfn_valid_within(buddy_pfn) &&
+	       page_is_buddy(higher_page, higher_buddy, order + 1);
+}
+
+/*
  * Freeing function for a buddy system allocator.
  *
  * The concept of a buddy system is to maintain direct-mapped table
@@ -905,11 +935,12 @@ static inline void __free_one_page(struct page *page,
 		struct zone *zone, unsigned int order,
 		int migratetype)
 {
-	unsigned long combined_pfn;
+	struct capture_control *capc = task_capc(zone);
 	unsigned long uninitialized_var(buddy_pfn);
-	struct page *buddy;
+	unsigned long combined_pfn;
+	struct free_area *area;
 	unsigned int max_order;
-	struct capture_control *capc = task_capc(zone);
+	struct page *buddy;
 
 	max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1);
 
@@ -978,35 +1009,12 @@ static inline void __free_one_page(struct page *page,
 done_merging:
 	set_page_order(page, order);
 
-	/*
-	 * If this is not the largest possible page, check if the buddy
-	 * of the next-highest order is free. If it is, it's possible
-	 * that pages are being freed that will coalesce soon. In case,
-	 * that is happening, add the free page to the tail of the list
-	 * so it's less likely to be used soon and more likely to be merged
-	 * as a higher order page
-	 */
-	if ((order < MAX_ORDER-2) && pfn_valid_within(buddy_pfn)
-			&& !is_shuffle_order(order)) {
-		struct page *higher_page, *higher_buddy;
-		combined_pfn = buddy_pfn & pfn;
-		higher_page = page + (combined_pfn - pfn);
-		buddy_pfn = __find_buddy_pfn(combined_pfn, order + 1);
-		higher_buddy = higher_page + (buddy_pfn - combined_pfn);
-		if (pfn_valid_within(buddy_pfn) &&
-		    page_is_buddy(higher_page, higher_buddy, order + 1)) {
-			add_to_free_area_tail(page, &zone->free_area[order],
-					      migratetype);
-			return;
-		}
-	}
-
-	if (is_shuffle_order(order))
-		add_to_free_area_random(page, &zone->free_area[order],
-				migratetype);
+	area = &zone->free_area[order];
+	if (is_shuffle_order(order) ? shuffle_add_to_tail() :
+	    buddy_merge_likely(pfn, buddy_pfn, page, order))
+		add_to_free_area_tail(page, area, migratetype);
 	else
-		add_to_free_area(page, &zone->free_area[order], migratetype);
-
+		add_to_free_area(page, area, migratetype);
 }
 
 /*
diff --git a/mm/shuffle.c b/mm/shuffle.c
index 3ce12481b1dc..55d592e62526 100644
--- a/mm/shuffle.c
+++ b/mm/shuffle.c
@@ -4,7 +4,6 @@
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/mmzone.h>
-#include <linux/random.h>
 #include <linux/moduleparam.h>
 #include "internal.h"
 #include "shuffle.h"
@@ -182,26 +181,3 @@ void __meminit __shuffle_free_memory(pg_data_t *pgdat)
 	for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
 		shuffle_zone(z);
 }
-
-void add_to_free_area_random(struct page *page, struct free_area *area,
-		int migratetype)
-{
-	static u64 rand;
-	static u8 rand_bits;
-
-	/*
-	 * The lack of locking is deliberate. If 2 threads race to
-	 * update the rand state it just adds to the entropy.
-	 */
-	if (rand_bits == 0) {
-		rand_bits = 64;
-		rand = get_random_u64();
-	}
-
-	if (rand & 1)
-		add_to_free_area(page, area, migratetype);
-	else
-		add_to_free_area_tail(page, area, migratetype);
-	rand_bits--;
-	rand >>= 1;
-}
diff --git a/mm/shuffle.h b/mm/shuffle.h
index 777a257a0d2f..add763cc0995 100644
--- a/mm/shuffle.h
+++ b/mm/shuffle.h
@@ -3,6 +3,7 @@
 #ifndef _MM_SHUFFLE_H
 #define _MM_SHUFFLE_H
 #include <linux/jump_label.h>
+#include <linux/random.h>
 
 /*
  * SHUFFLE_ENABLE is called from the command line enabling path, or by
@@ -43,6 +44,32 @@ static inline bool is_shuffle_order(int order)
 		return false;
 	return order >= SHUFFLE_ORDER;
 }
+
+static inline bool shuffle_add_to_tail(void)
+{
+	static u64 rand;
+	static u8 rand_bits;
+	u64 rand_old;
+
+	/*
+	 * The lack of locking is deliberate. If 2 threads race to
+	 * update the rand state it just adds to the entropy.
+	 */
+	if (rand_bits-- == 0) {
+		rand_bits = 64;
+		rand = get_random_u64();
+	}
+
+	/*
+	 * Test highest order bit while shifting our random value. This
+	 * should result in us testing for the carry flag following the
+	 * shift.
+	 */
+	rand_old = rand;
+	rand <<= 1;
+
+	return rand < rand_old;
+}
 #else
 static inline void shuffle_free_memory(pg_data_t *pgdat)
 {
@@ -60,5 +87,10 @@ static inline bool is_shuffle_order(int order)
 {
 	return false;
 }
+
+static inline bool shuffle_add_to_tail(void)
+{
+	return false;
+}
 #endif
 #endif /* _MM_SHUFFLE_H */


^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v4 2/6] mm: Move set/get_pcppage_migratetype to mmzone.h
  2019-08-07 22:41 [PATCH v4 0/6] mm / virtio: Provide support for unused page reporting Alexander Duyck
  2019-08-07 22:41 ` [PATCH v4 1/6] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
@ 2019-08-07 22:41 ` Alexander Duyck
  2019-08-07 22:42 ` [PATCH v4 3/6] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck
                   ` (6 subsequent siblings)
  8 siblings, 0 replies; 17+ messages in thread
From: Alexander Duyck @ 2019-08-07 22:41 UTC (permalink / raw)
  To: nitesh, kvm, david, mst, dave.hansen, linux-kernel, linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

In order to support page reporting it will be necessary to store and
retrieve the migratetype of a page. To enable that I am moving the set and
get operations for pcppage_migratetype into the mm/internal.h header so
that they can be used outside of the page_alloc.c file.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 mm/internal.h   |   18 ++++++++++++++++++
 mm/page_alloc.c |   18 ------------------
 2 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 0d5f720c75ab..e4a1a57bbd40 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -549,6 +549,24 @@ static inline bool is_migrate_highatomic_page(struct page *page)
 	return get_pageblock_migratetype(page) == MIGRATE_HIGHATOMIC;
 }
 
+/*
+ * A cached value of the page's pageblock's migratetype, used when the page is
+ * put on a pcplist. Used to avoid the pageblock migratetype lookup when
+ * freeing from pcplists in most cases, at the cost of possibly becoming stale.
+ * Also the migratetype set in the page does not necessarily match the pcplist
+ * index, e.g. page might have MIGRATE_CMA set but be on a pcplist with any
+ * other index - this ensures that it will be put on the correct CMA freelist.
+ */
+static inline int get_pcppage_migratetype(struct page *page)
+{
+	return page->index;
+}
+
+static inline void set_pcppage_migratetype(struct page *page, int migratetype)
+{
+	page->index = migratetype;
+}
+
 void setup_zone_pageset(struct zone *zone);
 extern struct page *alloc_new_node_page(struct page *page, unsigned long node);
 #endif	/* __MM_INTERNAL_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e3cb6e7aa296..f04192f5ec3c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -185,24 +185,6 @@ static int __init early_init_on_free(char *buf)
 }
 early_param("init_on_free", early_init_on_free);
 
-/*
- * A cached value of the page's pageblock's migratetype, used when the page is
- * put on a pcplist. Used to avoid the pageblock migratetype lookup when
- * freeing from pcplists in most cases, at the cost of possibly becoming stale.
- * Also the migratetype set in the page does not necessarily match the pcplist
- * index, e.g. page might have MIGRATE_CMA set but be on a pcplist with any
- * other index - this ensures that it will be put on the correct CMA freelist.
- */
-static inline int get_pcppage_migratetype(struct page *page)
-{
-	return page->index;
-}
-
-static inline void set_pcppage_migratetype(struct page *page, int migratetype)
-{
-	page->index = migratetype;
-}
-
 #ifdef CONFIG_PM_SLEEP
 /*
  * The following functions are used by the suspend/hibernate code to temporarily


^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v4 3/6] mm: Use zone and order instead of free area in free_list manipulators
  2019-08-07 22:41 [PATCH v4 0/6] mm / virtio: Provide support for unused page reporting Alexander Duyck
  2019-08-07 22:41 ` [PATCH v4 1/6] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
  2019-08-07 22:41 ` [PATCH v4 2/6] mm: Move set/get_pcppage_migratetype to mmzone.h Alexander Duyck
@ 2019-08-07 22:42 ` Alexander Duyck
  2019-08-07 22:42 ` [PATCH v4 4/6] mm: Introduce Reported pages Alexander Duyck
                   ` (5 subsequent siblings)
  8 siblings, 0 replies; 17+ messages in thread
From: Alexander Duyck @ 2019-08-07 22:42 UTC (permalink / raw)
  To: nitesh, kvm, david, mst, dave.hansen, linux-kernel, linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

In order to enable the use of the zone from the list manipulator functions
I will need access to the zone pointer. As it turns out most of the
accessors were always just being directly passed &zone->free_area[order]
anyway so it would make sense to just fold that into the function itself
and pass the zone and order as arguments instead of the free area.

In order to be able to reference the zone we need to move the declaration
of the functions down so that we have the zone defined before we define the
list manipulation functions.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 include/linux/mmzone.h |   70 ++++++++++++++++++++++++++----------------------
 mm/page_alloc.c        |   30 ++++++++-------------
 2 files changed, 49 insertions(+), 51 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index c6bd8e9bb476..2f2b6f968ed3 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -100,29 +100,6 @@ struct free_area {
 	unsigned long		nr_free;
 };
 
-/* Used for pages not on another list */
-static inline void add_to_free_area(struct page *page, struct free_area *area,
-			     int migratetype)
-{
-	list_add(&page->lru, &area->free_list[migratetype]);
-	area->nr_free++;
-}
-
-/* Used for pages not on another list */
-static inline void add_to_free_area_tail(struct page *page, struct free_area *area,
-				  int migratetype)
-{
-	list_add_tail(&page->lru, &area->free_list[migratetype]);
-	area->nr_free++;
-}
-
-/* Used for pages which are on another list */
-static inline void move_to_free_area(struct page *page, struct free_area *area,
-			     int migratetype)
-{
-	list_move(&page->lru, &area->free_list[migratetype]);
-}
-
 static inline struct page *get_page_from_free_area(struct free_area *area,
 					    int migratetype)
 {
@@ -130,15 +107,6 @@ static inline struct page *get_page_from_free_area(struct free_area *area,
 					struct page, lru);
 }
 
-static inline void del_page_from_free_area(struct page *page,
-		struct free_area *area)
-{
-	list_del(&page->lru);
-	__ClearPageBuddy(page);
-	set_page_private(page, 0);
-	area->nr_free--;
-}
-
 static inline bool free_area_empty(struct free_area *area, int migratetype)
 {
 	return list_empty(&area->free_list[migratetype]);
@@ -789,6 +757,44 @@ static inline bool pgdat_is_empty(pg_data_t *pgdat)
 	return !pgdat->node_start_pfn && !pgdat->node_spanned_pages;
 }
 
+/* Used for pages not on another list */
+static inline void add_to_free_list(struct page *page, struct zone *zone,
+				    unsigned int order, int migratetype)
+{
+	struct free_area *area = &zone->free_area[order];
+
+	list_add(&page->lru, &area->free_list[migratetype]);
+	area->nr_free++;
+}
+
+/* Used for pages not on another list */
+static inline void add_to_free_list_tail(struct page *page, struct zone *zone,
+					 unsigned int order, int migratetype)
+{
+	struct free_area *area = &zone->free_area[order];
+
+	list_add_tail(&page->lru, &area->free_list[migratetype]);
+	area->nr_free++;
+}
+
+/* Used for pages which are on another list */
+static inline void move_to_free_list(struct page *page, struct zone *zone,
+				     unsigned int order, int migratetype)
+{
+	struct free_area *area = &zone->free_area[order];
+
+	list_move(&page->lru, &area->free_list[migratetype]);
+}
+
+static inline void del_page_from_free_list(struct page *page, struct zone *zone,
+					   unsigned int order)
+{
+	list_del(&page->lru);
+	__ClearPageBuddy(page);
+	set_page_private(page, 0);
+	zone->free_area[order].nr_free--;
+}
+
 #include <linux/memory_hotplug.h>
 
 void build_all_zonelists(pg_data_t *pgdat);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f04192f5ec3c..4b5812c3800e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -920,7 +920,6 @@ static inline void __free_one_page(struct page *page,
 	struct capture_control *capc = task_capc(zone);
 	unsigned long uninitialized_var(buddy_pfn);
 	unsigned long combined_pfn;
-	struct free_area *area;
 	unsigned int max_order;
 	struct page *buddy;
 
@@ -957,7 +956,7 @@ static inline void __free_one_page(struct page *page,
 		if (page_is_guard(buddy))
 			clear_page_guard(zone, buddy, order, migratetype);
 		else
-			del_page_from_free_area(buddy, &zone->free_area[order]);
+			del_page_from_free_list(buddy, zone, order);
 		combined_pfn = buddy_pfn & pfn;
 		page = page + (combined_pfn - pfn);
 		pfn = combined_pfn;
@@ -991,12 +990,11 @@ static inline void __free_one_page(struct page *page,
 done_merging:
 	set_page_order(page, order);
 
-	area = &zone->free_area[order];
 	if (is_shuffle_order(order) ? shuffle_add_to_tail() :
 	    buddy_merge_likely(pfn, buddy_pfn, page, order))
-		add_to_free_area_tail(page, area, migratetype);
+		add_to_free_list_tail(page, zone, order, migratetype);
 	else
-		add_to_free_area(page, area, migratetype);
+		add_to_free_list(page, zone, order, migratetype);
 }
 
 /*
@@ -2000,13 +1998,11 @@ void __init init_cma_reserved_pageblock(struct page *page)
  * -- nyc
  */
 static inline void expand(struct zone *zone, struct page *page,
-	int low, int high, struct free_area *area,
-	int migratetype)
+	int low, int high, int migratetype)
 {
 	unsigned long size = 1 << high;
 
 	while (high > low) {
-		area--;
 		high--;
 		size >>= 1;
 		VM_BUG_ON_PAGE(bad_range(zone, &page[size]), &page[size]);
@@ -2020,7 +2016,7 @@ static inline void expand(struct zone *zone, struct page *page,
 		if (set_page_guard(zone, &page[size], high, migratetype))
 			continue;
 
-		add_to_free_area(&page[size], area, migratetype);
+		add_to_free_list(&page[size], zone, high, migratetype);
 		set_page_order(&page[size], high);
 	}
 }
@@ -2178,8 +2174,8 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
 		page = get_page_from_free_area(area, migratetype);
 		if (!page)
 			continue;
-		del_page_from_free_area(page, area);
-		expand(zone, page, order, current_order, area, migratetype);
+		del_page_from_free_list(page, zone, current_order);
+		expand(zone, page, order, current_order, migratetype);
 		set_pcppage_migratetype(page, migratetype);
 		return page;
 	}
@@ -2187,7 +2183,6 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
 	return NULL;
 }
 
-
 /*
  * This array describes the order lists are fallen back to when
  * the free lists for the desirable migrate type are depleted
@@ -2264,7 +2259,7 @@ static int move_freepages(struct zone *zone,
 		}
 
 		order = page_order(page);
-		move_to_free_area(page, &zone->free_area[order], migratetype);
+		move_to_free_list(page, zone, order, migratetype);
 		page += 1 << order;
 		pages_moved += 1 << order;
 	}
@@ -2380,7 +2375,6 @@ static void steal_suitable_fallback(struct zone *zone, struct page *page,
 		unsigned int alloc_flags, int start_type, bool whole_block)
 {
 	unsigned int current_order = page_order(page);
-	struct free_area *area;
 	int free_pages, movable_pages, alike_pages;
 	int old_block_type;
 
@@ -2451,8 +2445,7 @@ static void steal_suitable_fallback(struct zone *zone, struct page *page,
 	return;
 
 single_page:
-	area = &zone->free_area[current_order];
-	move_to_free_area(page, area, start_type);
+	move_to_free_list(page, zone, current_order, start_type);
 }
 
 /*
@@ -3123,7 +3116,6 @@ void split_page(struct page *page, unsigned int order)
 
 int __isolate_free_page(struct page *page, unsigned int order)
 {
-	struct free_area *area = &page_zone(page)->free_area[order];
 	unsigned long watermark;
 	struct zone *zone;
 	int mt;
@@ -3149,7 +3141,7 @@ int __isolate_free_page(struct page *page, unsigned int order)
 
 	/* Remove page from free list */
 
-	del_page_from_free_area(page, area);
+	del_page_from_free_list(page, zone, order);
 
 	/*
 	 * Set the pageblock if the isolated page is at least half of a
@@ -8568,7 +8560,7 @@ void zone_pcp_reset(struct zone *zone)
 		pr_info("remove from free list %lx %d %lx\n",
 			pfn, 1 << order, end_pfn);
 #endif
-		del_page_from_free_area(page, &zone->free_area[order]);
+		del_page_from_free_list(page, zone, order);
 		for (i = 0; i < (1 << order); i++)
 			SetPageReserved((page+i));
 		pfn += (1 << order);


^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v4 4/6] mm: Introduce Reported pages
  2019-08-07 22:41 [PATCH v4 0/6] mm / virtio: Provide support for unused page reporting Alexander Duyck
                   ` (2 preceding siblings ...)
  2019-08-07 22:42 ` [PATCH v4 3/6] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck
@ 2019-08-07 22:42 ` Alexander Duyck
  2019-08-08 13:45   ` Nitesh Narayan Lal
  2019-08-07 22:42 ` [PATCH v4 5/6] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck
                   ` (4 subsequent siblings)
  8 siblings, 1 reply; 17+ messages in thread
From: Alexander Duyck @ 2019-08-07 22:42 UTC (permalink / raw)
  To: nitesh, kvm, david, mst, dave.hansen, linux-kernel, linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

In order to pave the way for free page reporting in virtualized
environments we will need a way to get pages out of the free lists and
identify those pages after they have been returned. To accomplish this,
this patch adds the concept of a Reported Buddy, which is essentially
meant to just be the Uptodate flag used in conjunction with the Buddy
page type.

It adds a set of pointers we shall call "boundary" which represents the
upper boundary between the unreported and reported pages. The general idea
is that in order for a page to cross from one side of the boundary to the
other it will need to go through the reporting process. Ultimately a
free_list has been fully processed when the boundary has been moved from
the tail all they way up to occupying the first entry in the list.

Doing this we should be able to make certain that we keep the reported
pages as one contiguous block in each free list. This will allow us to
efficiently manipulate the free lists whenever we need to go in and start
sending reports to the hypervisor that there are new pages that have been
freed and are no longer in use.

An added advantage to this approach is that we should be reducing the
overall memory footprint of the guest as it will be more likely to recycle
warm pages versus trying to allocate the reported pages that were likely
evicted from the guest memory.

Since we will only be reporting one zone at a time we keep the boundary
limited to being defined for just the zone we are currently reporting pages
from. Doing this we can keep the number of additional pointers needed quite
small. To flag that the boundaries are in place we use a single bit
in the zone to indicate that reporting and the boundaries are active.

The determination of when to start reporting is based on the tracking of
the number of free pages in a given area versus the number of reported
pages in that area. We keep track of the number of reported pages per
free_area in a separate zone specific area. We do this to avoid modifying
the free_area structure as this can lead to false sharing for the highest
order with the zone lock which leads to a noticeable performance
degradation.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 include/linux/mmzone.h         |   40 +++++
 include/linux/page-flags.h     |   11 +
 include/linux/page_reporting.h |  138 ++++++++++++++++++
 mm/Kconfig                     |    5 +
 mm/Makefile                    |    1 
 mm/memory_hotplug.c            |    1 
 mm/page_alloc.c                |  136 +++++++++++++++++
 mm/page_reporting.c            |  313 ++++++++++++++++++++++++++++++++++++++++
 8 files changed, 637 insertions(+), 8 deletions(-)
 create mode 100644 include/linux/page_reporting.h
 create mode 100644 mm/page_reporting.c

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 2f2b6f968ed3..b8ed926552b1 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -462,6 +462,14 @@ struct zone {
 	seqlock_t		span_seqlock;
 #endif
 
+#ifdef CONFIG_PAGE_REPORTING
+	/*
+	 * Pointer to reported page tracking statistics array. The size of
+	 * the array is MAX_ORDER - PAGE_REPORTING_MIN_ORDER. NULL when
+	 * unused page reporting is not present.
+	 */
+	unsigned long		*reported_pages;
+#endif
 	int initialized;
 
 	/* Write-intensive fields used from the page allocator */
@@ -537,6 +545,14 @@ enum zone_flags {
 	ZONE_BOOSTED_WATERMARK,		/* zone recently boosted watermarks.
 					 * Cleared when kswapd is woken.
 					 */
+	ZONE_PAGE_REPORTING_REQUESTED,	/* zone enabled page reporting and has
+					 * requested flushing the data out of
+					 * higher order pages.
+					 */
+	ZONE_PAGE_REPORTING_ACTIVE,	/* zone enabled page reporting and is
+					 * activly flushing the data out of
+					 * higher order pages.
+					 */
 };
 
 static inline unsigned long zone_managed_pages(struct zone *zone)
@@ -757,6 +773,8 @@ static inline bool pgdat_is_empty(pg_data_t *pgdat)
 	return !pgdat->node_start_pfn && !pgdat->node_spanned_pages;
 }
 
+#include <linux/page_reporting.h>
+
 /* Used for pages not on another list */
 static inline void add_to_free_list(struct page *page, struct zone *zone,
 				    unsigned int order, int migratetype)
@@ -771,10 +789,16 @@ static inline void add_to_free_list(struct page *page, struct zone *zone,
 static inline void add_to_free_list_tail(struct page *page, struct zone *zone,
 					 unsigned int order, int migratetype)
 {
-	struct free_area *area = &zone->free_area[order];
+	struct list_head *tail = get_unreported_tail(zone, order, migratetype);
 
-	list_add_tail(&page->lru, &area->free_list[migratetype]);
-	area->nr_free++;
+	/*
+	 * To prevent the unreported pages from being interleaved with the
+	 * reported ones while we are actively processing pages we will use
+	 * the head of the reported pages to determine the tail of the free
+	 * list.
+	 */
+	list_add_tail(&page->lru, tail);
+	zone->free_area[order].nr_free++;
 }
 
 /* Used for pages which are on another list */
@@ -783,12 +807,22 @@ static inline void move_to_free_list(struct page *page, struct zone *zone,
 {
 	struct free_area *area = &zone->free_area[order];
 
+	/*
+	 * Clear Hinted flag, if present, to avoid placing reported pages
+	 * at the top of the free_list. It is cheaper to just process this
+	 * page again than to walk around a page that is already reported.
+	 */
+	clear_page_reported(page, zone);
+
 	list_move(&page->lru, &area->free_list[migratetype]);
 }
 
 static inline void del_page_from_free_list(struct page *page, struct zone *zone,
 					   unsigned int order)
 {
+	/* Clear Reported flag, if present, before resetting page type */
+	clear_page_reported(page, zone);
+
 	list_del(&page->lru);
 	__ClearPageBuddy(page);
 	set_page_private(page, 0);
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index f91cb8898ff0..759a3b3956f2 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -163,6 +163,9 @@ enum pageflags {
 
 	/* non-lru isolated movable page */
 	PG_isolated = PG_reclaim,
+
+	/* Buddy pages. Used to track which pages have been reported */
+	PG_reported = PG_uptodate,
 };
 
 #ifndef __GENERATING_BOUNDS_H
@@ -432,6 +435,14 @@ static inline bool set_hwpoison_free_buddy_page(struct page *page)
 #endif
 
 /*
+ * PageReported() is used to track reported free pages within the Buddy
+ * allocator. We can use the non-atomic version of the test and set
+ * operations as both should be shielded with the zone lock to prevent
+ * any possible races on the setting or clearing of the bit.
+ */
+__PAGEFLAG(Reported, reported, PF_NO_COMPOUND)
+
+/*
  * On an anonymous page mapped into a user virtual memory area,
  * page->mapping points to its anon_vma, not to a struct address_space;
  * with the PAGE_MAPPING_ANON bit set to distinguish it.  See rmap.h.
diff --git a/include/linux/page_reporting.h b/include/linux/page_reporting.h
new file mode 100644
index 000000000000..498bde6ea764
--- /dev/null
+++ b/include/linux/page_reporting.h
@@ -0,0 +1,138 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_PAGE_REPORTING_H
+#define _LINUX_PAGE_REPORTING_H
+
+#include <linux/mmzone.h>
+#include <linux/jump_label.h>
+#include <linux/pageblock-flags.h>
+#include <asm/pgtable_types.h>
+
+#define PAGE_REPORTING_MIN_ORDER	pageblock_order
+#define PAGE_REPORTING_HWM		32
+
+#ifdef CONFIG_PAGE_REPORTING
+struct page_reporting_dev_info {
+	/* function that alters pages to make them "reported" */
+	void (*report)(struct page_reporting_dev_info *phdev,
+		       unsigned int nents);
+
+	/* scatterlist containing pages to be processed */
+	struct scatterlist *sg;
+
+	/*
+	 * Upper limit on the number of pages that the react function
+	 * expects to be placed into the batch list to be processed.
+	 */
+	unsigned long capacity;
+
+	/* work struct for processing reports */
+	struct delayed_work work;
+
+	/*
+	 * The number of zones requesting reporting, plus one additional if
+	 * processing thread is active.
+	 */
+	atomic_t refcnt;
+};
+
+extern struct static_key page_reporting_notify_enabled;
+
+/* Boundary functions */
+struct list_head *__page_reporting_get_boundary(unsigned int order,
+						int migratetype);
+void page_reporting_del_from_boundary(struct page *page, struct zone *zone);
+void page_reporting_add_to_boundary(struct page *page, struct zone *zone,
+				    int migratetype);
+
+/* Hinted page accessors, defined in page_alloc.c */
+struct page *get_unreported_page(struct zone *zone, unsigned int order,
+				 int migratetype);
+void put_reported_page(struct zone *zone, struct page *page);
+
+void __page_reporting_request(struct zone *zone);
+void __page_reporting_free_stats(struct zone *zone);
+
+/* Tear-down and bring-up for page reporting devices */
+void page_reporting_shutdown(struct page_reporting_dev_info *phdev);
+int page_reporting_startup(struct page_reporting_dev_info *phdev);
+#endif /* CONFIG_PAGE_REPORTING */
+
+static inline struct list_head *
+get_unreported_tail(struct zone *zone, unsigned int order, int migratetype)
+{
+#ifdef CONFIG_PAGE_REPORTING
+	if (order >= PAGE_REPORTING_MIN_ORDER &&
+	    test_bit(ZONE_PAGE_REPORTING_ACTIVE, &zone->flags))
+		return __page_reporting_get_boundary(order, migratetype);
+#endif
+	return &zone->free_area[order].free_list[migratetype];
+}
+
+static inline void clear_page_reported(struct page *page,
+				     struct zone *zone)
+{
+#ifdef CONFIG_PAGE_REPORTING
+	if (likely(!PageReported(page)))
+		return;
+
+	/* push boundary back if we removed the upper boundary */
+	if (test_bit(ZONE_PAGE_REPORTING_ACTIVE, &zone->flags))
+		page_reporting_del_from_boundary(page, zone);
+
+	__ClearPageReported(page);
+
+	/* page_private will contain the page order, so just use it directly */
+	zone->reported_pages[page_private(page) - PAGE_REPORTING_MIN_ORDER]--;
+#endif
+}
+
+/* Free reported_pages and reset reported page tracking count to 0 */
+static inline void page_reporting_reset(struct zone *zone)
+{
+#ifdef CONFIG_PAGE_REPORTING
+	if (zone->reported_pages)
+		__page_reporting_free_stats(zone);
+#endif
+}
+
+/**
+ * page_reporting_notify_free - Free page notification to start page processing
+ * @zone: Pointer to current zone of last page processed
+ * @order: Order of last page added to zone
+ *
+ * This function is meant to act as a screener for __page_reporting_request
+ * which will determine if a give zone has crossed over the high-water mark
+ * that will justify us beginning page treatment. If we have crossed that
+ * threshold then it will start the process of pulling some pages and
+ * placing them in the batch list for treatment.
+ */
+static inline void page_reporting_notify_free(struct zone *zone, int order)
+{
+#ifdef CONFIG_PAGE_REPORTING
+	unsigned long nr_reported;
+
+	/* Called from hot path in __free_one_page() */
+	if (!static_key_false(&page_reporting_notify_enabled))
+		return;
+
+	/* Limit notifications only to higher order pages */
+	if (order < PAGE_REPORTING_MIN_ORDER)
+		return;
+
+	/* Do not bother with tests if we have already requested reporting */
+	if (test_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags))
+		return;
+
+	/* If reported_pages is not populated, assume 0 */
+	nr_reported = zone->reported_pages ?
+		    zone->reported_pages[order - PAGE_REPORTING_MIN_ORDER] : 0;
+
+	/* Only request it if we have enough to begin the page reporting */
+	if (zone->free_area[order].nr_free < nr_reported + PAGE_REPORTING_HWM)
+		return;
+
+	/* This is slow, but should be called very rarely */
+	__page_reporting_request(zone);
+#endif
+}
+#endif /*_LINUX_PAGE_REPORTING_H */
diff --git a/mm/Kconfig b/mm/Kconfig
index 06f758786e4a..52c6c49f0f69 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -237,6 +237,11 @@ config COMPACTION
           linux-mm@kvack.org.
 
 #
+# support for unused page reporting
+config PAGE_REPORTING
+	bool
+
+#
 # support for page migration
 #
 config MIGRATION
diff --git a/mm/Makefile b/mm/Makefile
index d0b295c3b764..1e17ba0ed2f0 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -105,3 +105,4 @@ obj-$(CONFIG_PERCPU_STATS) += percpu-stats.o
 obj-$(CONFIG_ZONE_DEVICE) += memremap.o
 obj-$(CONFIG_HMM_MIRROR) += hmm.o
 obj-$(CONFIG_MEMFD_CREATE) += memfd.o
+obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 5b8811945bbb..bd40beac293b 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1612,6 +1612,7 @@ static int __ref __offline_pages(unsigned long start_pfn,
 	if (!populated_zone(zone)) {
 		zone_pcp_reset(zone);
 		build_all_zonelists(NULL);
+		page_reporting_reset(zone);
 	} else
 		zone_pcp_update(zone);
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4b5812c3800e..d0d3fb12ba54 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -68,6 +68,7 @@
 #include <linux/lockdep.h>
 #include <linux/nmi.h>
 #include <linux/psi.h>
+#include <linux/page_reporting.h>
 
 #include <asm/sections.h>
 #include <asm/tlbflush.h>
@@ -915,7 +916,7 @@ static inline struct capture_control *task_capc(struct zone *zone)
 static inline void __free_one_page(struct page *page,
 		unsigned long pfn,
 		struct zone *zone, unsigned int order,
-		int migratetype)
+		int migratetype, bool reported)
 {
 	struct capture_control *capc = task_capc(zone);
 	unsigned long uninitialized_var(buddy_pfn);
@@ -990,11 +991,20 @@ static inline void __free_one_page(struct page *page,
 done_merging:
 	set_page_order(page, order);
 
-	if (is_shuffle_order(order) ? shuffle_add_to_tail() :
-	    buddy_merge_likely(pfn, buddy_pfn, page, order))
+	if (reported ||
+	    (is_shuffle_order(order) ? shuffle_add_to_tail() :
+	     buddy_merge_likely(pfn, buddy_pfn, page, order)))
 		add_to_free_list_tail(page, zone, order, migratetype);
 	else
 		add_to_free_list(page, zone, order, migratetype);
+
+	/*
+	 * No need to notify on a reported page as the total count of
+	 * unreported pages will not have increased since we have essentially
+	 * merged the reported page with one or more unreported pages.
+	 */
+	if (!reported)
+		page_reporting_notify_free(zone, order);
 }
 
 /*
@@ -1305,7 +1315,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
 		if (unlikely(isolated_pageblocks))
 			mt = get_pageblock_migratetype(page);
 
-		__free_one_page(page, page_to_pfn(page), zone, 0, mt);
+		__free_one_page(page, page_to_pfn(page), zone, 0, mt, false);
 		trace_mm_page_pcpu_drain(page, 0, mt);
 	}
 	spin_unlock(&zone->lock);
@@ -1321,7 +1331,7 @@ static void free_one_page(struct zone *zone,
 		is_migrate_isolate(migratetype))) {
 		migratetype = get_pfnblock_migratetype(page, pfn);
 	}
-	__free_one_page(page, pfn, zone, order, migratetype);
+	__free_one_page(page, pfn, zone, order, migratetype, false);
 	spin_unlock(&zone->lock);
 }
 
@@ -2183,6 +2193,122 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
 	return NULL;
 }
 
+#ifdef CONFIG_PAGE_REPORTING
+/**
+ * get_unreported_page - Pull an unreported page from the free_list
+ * @zone: Zone to draw pages from
+ * @order: Order to draw pages from
+ * @mt: Migratetype to draw pages from
+ *
+ * This function will obtain a page from the free list. It will start by
+ * attempting to pull from the tail of the free list and if that is already
+ * reported on it will instead pull the head if that is unreported.
+ *
+ * The page will have the migrate type and order stored in the page
+ * metadata. While being processed the page will not be avaialble for
+ * allocation.
+ *
+ * Return: page pointer if raw page found, otherwise NULL
+ */
+struct page *get_unreported_page(struct zone *zone, unsigned int order, int mt)
+{
+	struct list_head *tail = get_unreported_tail(zone, order, mt);
+	struct free_area *area = &(zone->free_area[order]);
+	struct list_head *list = &area->free_list[mt];
+	struct page *page;
+
+	/* zone lock should be held when this function is called */
+	lockdep_assert_held(&zone->lock);
+
+	/* Find a page of the appropriate size in the preferred list */
+	page = list_last_entry(tail, struct page, lru);
+	list_for_each_entry_from_reverse(page, list, lru) {
+		/* If we entered this loop then the "raw" list isn't empty */
+
+		/* If the page is reported try the head of the list */
+		if (PageReported(page)) {
+			page = list_first_entry(list, struct page, lru);
+
+			/*
+			 * If both the head and tail are reported then reset
+			 * the boundary so that we read as an empty list
+			 * next time and bail out.
+			 */
+			if (PageReported(page)) {
+				page_reporting_add_to_boundary(page, zone, mt);
+				break;
+			}
+		}
+
+		del_page_from_free_list(page, zone, order);
+
+		/* record migratetype and order within page */
+		set_pcppage_migratetype(page, mt);
+		set_page_private(page, order);
+
+		/*
+		 * Page will not be available for allocation while we are
+		 * processing it so update the freepage state.
+		 */
+		__mod_zone_freepage_state(zone, -(1 << order), mt);
+
+		return page;
+	}
+
+	return NULL;
+}
+
+/**
+ * put_reported_page - Return a now-reported page back where we got it
+ * @zone: Zone to return pages to
+ * @page: Page that was reported
+ *
+ * This function will pull the migratetype and order information out
+ * of the page and attempt to return it where it found it. If the page
+ * is added to the free list without changes we will mark it as being
+ * reported.
+ */
+void put_reported_page(struct zone *zone, struct page *page)
+{
+	unsigned int order, mt;
+	unsigned long pfn;
+
+	/* zone lock should be held when this function is called */
+	lockdep_assert_held(&zone->lock);
+
+	mt = get_pcppage_migratetype(page);
+	pfn = page_to_pfn(page);
+
+	if (unlikely(has_isolate_pageblock(zone) || is_migrate_isolate(mt))) {
+		mt = get_pfnblock_migratetype(page, pfn);
+		set_pcppage_migratetype(page, mt);
+	}
+
+	order = page_private(page);
+	set_page_private(page, 0);
+
+	__free_one_page(page, pfn, zone, order, mt, true);
+
+	/*
+	 * If page was comingled with another page we cannot consider
+	 * the result to be "reported" since part of the page hasn't been.
+	 * In this case we will simply exit and not update the "reported"
+	 * state. Instead just treat the result as a unreported page.
+	 */
+	if (!PageBuddy(page) || page_order(page) != order)
+		return;
+
+	/* update areated page accounting */
+	zone->reported_pages[order - PAGE_REPORTING_MIN_ORDER]++;
+
+	/* update boundary of new migratetype and record it */
+	page_reporting_add_to_boundary(page, zone, mt);
+
+	/* flag page as reported */
+	__SetPageReported(page);
+}
+#endif /* CONFIG_PAGE_REPORTING */
+
 /*
  * This array describes the order lists are fallen back to when
  * the free lists for the desirable migrate type are depleted
diff --git a/mm/page_reporting.c b/mm/page_reporting.c
new file mode 100644
index 000000000000..ae26dd77bce9
--- /dev/null
+++ b/mm/page_reporting.c
@@ -0,0 +1,313 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/mm.h>
+#include <linux/mmzone.h>
+#include <linux/page-isolation.h>
+#include <linux/gfp.h>
+#include <linux/export.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/scatterlist.h>
+#include "internal.h"
+
+static struct page_reporting_dev_info __rcu *ph_dev_info __read_mostly;
+struct static_key page_reporting_notify_enabled;
+
+struct list_head *boundary[MAX_ORDER - PAGE_REPORTING_MIN_ORDER][MIGRATE_TYPES];
+
+static void page_reporting_reset_boundary(struct zone *zone, unsigned int order,
+					  unsigned int migratetype)
+{
+	boundary[order - PAGE_REPORTING_MIN_ORDER][migratetype] =
+			&zone->free_area[order].free_list[migratetype];
+}
+
+#define for_each_reporting_migratetype_order(_order, _type) \
+	for (_order = MAX_ORDER; _order-- != PAGE_REPORTING_MIN_ORDER;) \
+		for (_type = MIGRATE_TYPES; _type--;)
+
+static int page_reporting_populate_metadata(struct zone *zone)
+{
+	unsigned int order, mt;
+
+	/*
+	 * We need to make sure we have somewhere to store the tracking
+	 * data for how many reported pages are in the zone. To do that
+	 * we need to make certain zone->reported_pages is populated.
+	 */
+	if (!zone->reported_pages) {
+		zone->reported_pages =
+			kcalloc(MAX_ORDER - PAGE_REPORTING_MIN_ORDER,
+				sizeof(unsigned long),
+				GFP_KERNEL);
+		if (!zone->reported_pages)
+			return -ENOMEM;
+	}
+
+	/* Update boundary data to reflect the zone we are currently working */
+	for_each_reporting_migratetype_order(order, mt)
+		page_reporting_reset_boundary(zone, order, mt);
+
+	return 0;
+}
+
+struct list_head *__page_reporting_get_boundary(unsigned int order,
+						int migratetype)
+{
+	return boundary[order - PAGE_REPORTING_MIN_ORDER][migratetype];
+}
+
+void page_reporting_del_from_boundary(struct page *page, struct zone *zone)
+{
+	unsigned int order = page_private(page) - PAGE_REPORTING_MIN_ORDER;
+	int mt = get_pcppage_migratetype(page);
+	struct list_head **tail = &boundary[order][mt];
+
+	if (*tail == &page->lru)
+		*tail = page->lru.next;
+}
+
+void page_reporting_add_to_boundary(struct page *page, struct zone *zone,
+				    int migratetype)
+{
+	unsigned int order = page_private(page) - PAGE_REPORTING_MIN_ORDER;
+	struct list_head **tail = &boundary[order][migratetype];
+
+	*tail = &page->lru;
+}
+
+static unsigned int page_reporting_fill(struct zone *zone,
+					struct page_reporting_dev_info *phdev)
+{
+	struct scatterlist *sg = phdev->sg;
+	unsigned int order, mt, count = 0;
+
+	sg_init_table(phdev->sg, phdev->capacity);
+
+	for_each_reporting_migratetype_order(order, mt) {
+		struct page *page;
+
+		/*
+		 * Pull pages from free list until we have drained
+		 * it or we have reached capacity.
+		 */
+		while ((page = get_unreported_page(zone, order, mt))) {
+			sg_set_page(&sg[count], page, PAGE_SIZE << order, 0);
+
+			if (++count == phdev->capacity)
+				return count;
+		}
+	}
+
+	/* mark end of scatterlist due to underflow */
+	if (count)
+		sg_mark_end(&sg[count - 1]);
+
+	/*
+	 * If there are no longer enough free pages to fully populate
+	 * the scatterlist, then we can just shut it down for this zone.
+	 */
+	__clear_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags);
+	atomic_dec(&phdev->refcnt);
+
+	return count;
+}
+
+static void page_reporting_drain(struct zone *zone,
+				 struct page_reporting_dev_info *phdev)
+{
+	struct scatterlist *sg = phdev->sg;
+
+	/*
+	 * Drain the now reported pages back into their respective
+	 * free lists/areas. We assume at least one page is populated.
+	 */
+	do {
+		put_reported_page(zone, sg_page(sg));
+	} while (!sg_is_last(sg++));
+}
+
+/*
+ * The page reporting cycle consists of 4 stages, fill, report, drain, and idle.
+ * We will cycle through the first 3 stages until we fail to obtain any
+ * pages, in that case we will switch to idle.
+ */
+static void page_reporting_cycle(struct zone *zone,
+				 struct page_reporting_dev_info *phdev)
+{
+	/*
+	 * Guarantee boundaries and stats are populated before we
+	 * start placing reported pages in the zone.
+	 */
+	if (page_reporting_populate_metadata(zone))
+		return;
+
+	spin_lock(&zone->lock);
+
+	/* set bit indicating boundaries are present */
+	__set_bit(ZONE_PAGE_REPORTING_ACTIVE, &zone->flags);
+
+	do {
+		/* Pull pages out of allocator into a scaterlist */
+		unsigned int nents = page_reporting_fill(zone, phdev);
+
+		/* no pages were acquired, give up */
+		if (!nents)
+			break;
+
+		spin_unlock(&zone->lock);
+
+		/* begin processing pages in local list */
+		phdev->report(phdev, nents);
+
+		spin_lock(&zone->lock);
+
+		/*
+		 * We should have a scatterlist of pages that have been
+		 * processed. Return them to their original free lists.
+		 */
+		page_reporting_drain(zone, phdev);
+
+		/* keep pulling pages till there are none to pull */
+	} while (test_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags));
+
+	/* processing of the zone is complete, we can disable boundaries */
+	__clear_bit(ZONE_PAGE_REPORTING_ACTIVE, &zone->flags);
+
+	spin_unlock(&zone->lock);
+}
+
+static void page_reporting_process(struct work_struct *work)
+{
+	struct delayed_work *d_work = to_delayed_work(work);
+	struct page_reporting_dev_info *phdev =
+		container_of(d_work, struct page_reporting_dev_info, work);
+	struct zone *zone = first_online_pgdat()->node_zones;
+
+	do {
+		if (test_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags))
+			page_reporting_cycle(zone, phdev);
+
+		/*
+		 * Move to next zone, if at the end of the list
+		 * test to see if we can just go into idle.
+		 */
+		zone = next_zone(zone);
+		if (zone)
+			continue;
+		zone = first_online_pgdat()->node_zones;
+
+		/*
+		 * As long as refcnt has not reached zero there are still
+		 * zones to be processed.
+		 */
+	} while (atomic_read(&phdev->refcnt));
+}
+
+/* request page reporting on this zone */
+void __page_reporting_request(struct zone *zone)
+{
+	struct page_reporting_dev_info *phdev;
+
+	rcu_read_lock();
+
+	/*
+	 * We use RCU to protect the ph_dev_info pointer. In almost all
+	 * cases this should be present, however in the unlikely case of
+	 * a shutdown this will be NULL and we should exit.
+	 */
+	phdev = rcu_dereference(ph_dev_info);
+	if (unlikely(!phdev))
+		return;
+
+	/*
+	 * We can use separate test and set operations here as there
+	 * is nothing else that can set or clear this bit while we are
+	 * holding the zone lock. The advantage to doing it this way is
+	 * that we don't have to dirty the cacheline unless we are
+	 * changing the value.
+	 */
+	__set_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags);
+
+	/*
+	 * Delay the start of work to allow a sizable queue to
+	 * build. For now we are limiting this to running no more
+	 * than 10 times per second.
+	 */
+	if (!atomic_fetch_inc(&phdev->refcnt))
+		schedule_delayed_work(&phdev->work, HZ / 10);
+
+	rcu_read_unlock();
+}
+
+void __page_reporting_free_stats(struct zone *zone)
+{
+	/* free reported_page statisitics */
+	kfree(zone->reported_pages);
+	zone->reported_pages = NULL;
+}
+
+static DEFINE_MUTEX(page_reporting_mutex);
+
+void page_reporting_shutdown(struct page_reporting_dev_info *phdev)
+{
+	mutex_lock(page_reporting_mutex);
+
+	if (rcu_access_pointer(ph_dev_info) == phdev) {
+		/* Disable page reporting notification */
+		static_key_slow_dec(&page_reporting_notify_enabled);
+		RCU_INIT_POINTER(ph_dev_info, NULL);
+		synchronize_rcu();
+
+		/* Flush any existing work, and lock it out */
+		cancel_delayed_work_sync(&phdev->work);
+
+		/* Free scatterlist */
+		kfree(phdev->sg);
+		phdev->sg = NULL;
+	}
+
+	mutex_unlock(page_reporting_mutex);
+}
+EXPORT_SYMBOL_GPL(page_reporting_shutdown);
+
+int page_reporting_startup(struct page_reporting_dev_info *phdev)
+{
+	struct zone *zone;
+	int err = 0;
+
+	mutex_lock(page_reporting_mutex);
+
+	/* nothing to do if already in use */
+	if (rcu_access_pointer(ph_dev_info)) {
+		err = -EBUSY;
+		goto err_out;
+	}
+
+	/* allocate scatterlist to store pages being reported on */
+	phdev->sg = kcalloc(phdev->capacity, sizeof(*phdev->sg), GFP_KERNEL);
+	if (!phdev->sg) {
+		err = -ENOMEM;
+		goto err_out;
+	}
+
+	/* initialize refcnt and work structures */
+	atomic_set(&phdev->refcnt, 0);
+	INIT_DELAYED_WORK(&phdev->work, &page_reporting_process);
+
+	/* assign device, and begin initial flush of populated zones */
+	rcu_assign_pointer(ph_dev_info, phdev);
+	for_each_populated_zone(zone) {
+		spin_lock(&zone->lock);
+		__page_reporting_request(zone);
+		spin_unlock(&zone->lock);
+	}
+
+	/* enable page reporting notification */
+	static_key_slow_inc(&page_reporting_notify_enabled);
+err_out:
+	mutex_unlock(page_reporting_mutex);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(page_reporting_startup);
+


^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v4 5/6] virtio-balloon: Pull page poisoning config out of free page hinting
  2019-08-07 22:41 [PATCH v4 0/6] mm / virtio: Provide support for unused page reporting Alexander Duyck
                   ` (3 preceding siblings ...)
  2019-08-07 22:42 ` [PATCH v4 4/6] mm: Introduce Reported pages Alexander Duyck
@ 2019-08-07 22:42 ` Alexander Duyck
  2019-08-07 22:42 ` [PATCH v4 6/6] virtio-balloon: Add support for providing unused page reports to host Alexander Duyck
                   ` (3 subsequent siblings)
  8 siblings, 0 replies; 17+ messages in thread
From: Alexander Duyck @ 2019-08-07 22:42 UTC (permalink / raw)
  To: nitesh, kvm, david, mst, dave.hansen, linux-kernel, linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

Currently the page poisoning setting wasn't being enabled unless free page
hinting was enabled. However we will need the page poisoning tracking logic
as well for unused page reporting. As such pull it out and make it a
separate bit of config in the probe function.

In addition we can actually wrap the code in a check for NO_SANITY. If we
don't care what is actually in the page we can just default to 0 and leave
it there.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 drivers/virtio/virtio_balloon.c |   19 +++++++++++++------
 mm/page_reporting.c             |    8 ++++----
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 226fbb995fb0..2c19457ab573 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -842,7 +842,6 @@ static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
 static int virtballoon_probe(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb;
-	__u32 poison_val;
 	int err;
 
 	if (!vdev->config->get) {
@@ -909,11 +908,19 @@ static int virtballoon_probe(struct virtio_device *vdev)
 						  VIRTIO_BALLOON_CMD_ID_STOP);
 		spin_lock_init(&vb->free_page_list_lock);
 		INIT_LIST_HEAD(&vb->free_page_list);
-		if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
-			memset(&poison_val, PAGE_POISON, sizeof(poison_val));
-			virtio_cwrite(vb->vdev, struct virtio_balloon_config,
-				      poison_val, &poison_val);
-		}
+	}
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
+		__u32 poison_val = 0;
+
+#if !defined(CONFIG_PAGE_POISONING_NO_SANITY)
+		/*
+		 * Let hypervisor know that we are expecting a specific
+		 * value to be written back in unused pages.
+		 */
+		memset(&poison_val, PAGE_POISON, sizeof(poison_val));
+#endif
+		virtio_cwrite(vb->vdev, struct virtio_balloon_config,
+			      poison_val, &poison_val);
 	}
 	/*
 	 * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
diff --git a/mm/page_reporting.c b/mm/page_reporting.c
index ae26dd77bce9..68dccfc7d629 100644
--- a/mm/page_reporting.c
+++ b/mm/page_reporting.c
@@ -250,7 +250,7 @@ void __page_reporting_free_stats(struct zone *zone)
 
 void page_reporting_shutdown(struct page_reporting_dev_info *phdev)
 {
-	mutex_lock(page_reporting_mutex);
+	mutex_lock(&page_reporting_mutex);
 
 	if (rcu_access_pointer(ph_dev_info) == phdev) {
 		/* Disable page reporting notification */
@@ -266,7 +266,7 @@ void page_reporting_shutdown(struct page_reporting_dev_info *phdev)
 		phdev->sg = NULL;
 	}
 
-	mutex_unlock(page_reporting_mutex);
+	mutex_unlock(&page_reporting_mutex);
 }
 EXPORT_SYMBOL_GPL(page_reporting_shutdown);
 
@@ -275,7 +275,7 @@ int page_reporting_startup(struct page_reporting_dev_info *phdev)
 	struct zone *zone;
 	int err = 0;
 
-	mutex_lock(page_reporting_mutex);
+	mutex_lock(&page_reporting_mutex);
 
 	/* nothing to do if already in use */
 	if (rcu_access_pointer(ph_dev_info)) {
@@ -305,7 +305,7 @@ int page_reporting_startup(struct page_reporting_dev_info *phdev)
 	/* enable page reporting notification */
 	static_key_slow_inc(&page_reporting_notify_enabled);
 err_out:
-	mutex_unlock(page_reporting_mutex);
+	mutex_unlock(&page_reporting_mutex);
 
 	return err;
 }


^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v4 6/6] virtio-balloon: Add support for providing unused page reports to host
  2019-08-07 22:41 [PATCH v4 0/6] mm / virtio: Provide support for unused page reporting Alexander Duyck
                   ` (4 preceding siblings ...)
  2019-08-07 22:42 ` [PATCH v4 5/6] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck
@ 2019-08-07 22:42 ` Alexander Duyck
  2019-08-12  9:53   ` Michael S. Tsirkin
  2019-08-07 22:43 ` [PATCH v4 QEMU 1/3] virtio-ballon: Implement support for page poison tracking feature Alexander Duyck
                   ` (2 subsequent siblings)
  8 siblings, 1 reply; 17+ messages in thread
From: Alexander Duyck @ 2019-08-07 22:42 UTC (permalink / raw)
  To: nitesh, kvm, david, mst, dave.hansen, linux-kernel, linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

Add support for the page reporting feature provided by virtio-balloon.
Reporting differs from the regular balloon functionality in that is is
much less durable than a standard memory balloon. Instead of creating a
list of pages that cannot be accessed the pages are only inaccessible
while they are being indicated to the virtio interface. Once the
interface has acknowledged them they are placed back into their respective
free lists and are once again accessible by the guest system.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 drivers/virtio/Kconfig              |    1 +
 drivers/virtio/virtio_balloon.c     |   65 +++++++++++++++++++++++++++++++++++
 include/uapi/linux/virtio_balloon.h |    1 +
 3 files changed, 67 insertions(+)

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 078615cf2afc..4b2dd8259ff5 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -58,6 +58,7 @@ config VIRTIO_BALLOON
 	tristate "Virtio balloon driver"
 	depends on VIRTIO
 	select MEMORY_BALLOON
+	select PAGE_REPORTING
 	---help---
 	 This driver supports increasing and decreasing the amount
 	 of memory within a KVM guest.
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 2c19457ab573..52f9eeda1877 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -19,6 +19,7 @@
 #include <linux/mount.h>
 #include <linux/magic.h>
 #include <linux/pseudo_fs.h>
+#include <linux/page_reporting.h>
 
 /*
  * Balloon device works in 4K page units.  So each page is pointed to by
@@ -37,6 +38,9 @@
 #define VIRTIO_BALLOON_FREE_PAGE_SIZE \
 	(1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT))
 
+/*  limit on the number of pages that can be on the reporting vq */
+#define VIRTIO_BALLOON_VRING_HINTS_MAX	16
+
 #ifdef CONFIG_BALLOON_COMPACTION
 static struct vfsmount *balloon_mnt;
 #endif
@@ -46,6 +50,7 @@ enum virtio_balloon_vq {
 	VIRTIO_BALLOON_VQ_DEFLATE,
 	VIRTIO_BALLOON_VQ_STATS,
 	VIRTIO_BALLOON_VQ_FREE_PAGE,
+	VIRTIO_BALLOON_VQ_REPORTING,
 	VIRTIO_BALLOON_VQ_MAX
 };
 
@@ -113,6 +118,10 @@ struct virtio_balloon {
 
 	/* To register a shrinker to shrink memory upon memory pressure */
 	struct shrinker shrinker;
+
+	/* Unused page reporting device */
+	struct virtqueue *reporting_vq;
+	struct page_reporting_dev_info ph_dev_info;
 };
 
 static struct virtio_device_id id_table[] = {
@@ -152,6 +161,32 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 
 }
 
+void virtballoon_unused_page_report(struct page_reporting_dev_info *ph_dev_info,
+				    unsigned int nents)
+{
+	struct virtio_balloon *vb =
+		container_of(ph_dev_info, struct virtio_balloon, ph_dev_info);
+	struct virtqueue *vq = vb->reporting_vq;
+	unsigned int unused, err;
+
+	/* We should always be able to add these buffers to an empty queue. */
+	err = virtqueue_add_inbuf(vq, ph_dev_info->sg, nents, vb,
+				  GFP_NOWAIT | __GFP_NOWARN);
+
+	/*
+	 * In the extremely unlikely case that something has changed and we
+	 * are able to trigger an error we will simply display a warning
+	 * and exit without actually processing the pages.
+	 */
+	if (WARN_ON(err))
+		return;
+
+	virtqueue_kick(vq);
+
+	/* When host has read buffer, this completes via balloon_ack */
+	wait_event(vb->acked, virtqueue_get_buf(vq, &unused));
+}
+
 static void set_page_pfns(struct virtio_balloon *vb,
 			  __virtio32 pfns[], struct page *page)
 {
@@ -476,6 +511,7 @@ static int init_vqs(struct virtio_balloon *vb)
 	names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
 	names[VIRTIO_BALLOON_VQ_STATS] = NULL;
 	names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
+	names[VIRTIO_BALLOON_VQ_REPORTING] = NULL;
 
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 		names[VIRTIO_BALLOON_VQ_STATS] = "stats";
@@ -487,11 +523,19 @@ static int init_vqs(struct virtio_balloon *vb)
 		callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
 	}
 
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
+		names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq";
+		callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack;
+	}
+
 	err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
 					 vqs, callbacks, names, NULL, NULL);
 	if (err)
 		return err;
 
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
+		vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
+
 	vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
 	vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
@@ -931,12 +975,30 @@ static int virtballoon_probe(struct virtio_device *vdev)
 		if (err)
 			goto out_del_balloon_wq;
 	}
+
+	vb->ph_dev_info.report = virtballoon_unused_page_report;
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
+		unsigned int capacity;
+
+		capacity = min_t(unsigned int,
+				 virtqueue_get_vring_size(vb->reporting_vq) - 1,
+				 VIRTIO_BALLOON_VRING_HINTS_MAX);
+		vb->ph_dev_info.capacity = capacity;
+
+		err = page_reporting_startup(&vb->ph_dev_info);
+		if (err)
+			goto out_unregister_shrinker;
+	}
+
 	virtio_device_ready(vdev);
 
 	if (towards_target(vb))
 		virtballoon_changed(vdev);
 	return 0;
 
+out_unregister_shrinker:
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+		virtio_balloon_unregister_shrinker(vb);
 out_del_balloon_wq:
 	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 		destroy_workqueue(vb->balloon_wq);
@@ -965,6 +1027,8 @@ static void virtballoon_remove(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb = vdev->priv;
 
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
+		page_reporting_shutdown(&vb->ph_dev_info);
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 		virtio_balloon_unregister_shrinker(vb);
 	spin_lock_irq(&vb->stop_update_lock);
@@ -1034,6 +1098,7 @@ static int virtballoon_validate(struct virtio_device *vdev)
 	VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
 	VIRTIO_BALLOON_F_FREE_PAGE_HINT,
 	VIRTIO_BALLOON_F_PAGE_POISON,
+	VIRTIO_BALLOON_F_REPORTING,
 };
 
 static struct virtio_driver virtio_balloon_driver = {
diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index a1966cd7b677..19974392d324 100644
--- a/include/uapi/linux/virtio_balloon.h
+++ b/include/uapi/linux/virtio_balloon.h
@@ -36,6 +36,7 @@
 #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */
 #define VIRTIO_BALLOON_F_FREE_PAGE_HINT	3 /* VQ to report free pages */
 #define VIRTIO_BALLOON_F_PAGE_POISON	4 /* Guest is using page poisoning */
+#define VIRTIO_BALLOON_F_REPORTING	5 /* Page reporting virtqueue */
 
 /* Size of a PFN in the balloon interface. */
 #define VIRTIO_BALLOON_PFN_SHIFT 12


^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v4 QEMU 1/3] virtio-ballon: Implement support for page poison tracking feature
  2019-08-07 22:41 [PATCH v4 0/6] mm / virtio: Provide support for unused page reporting Alexander Duyck
                   ` (5 preceding siblings ...)
  2019-08-07 22:42 ` [PATCH v4 6/6] virtio-balloon: Add support for providing unused page reports to host Alexander Duyck
@ 2019-08-07 22:43 ` Alexander Duyck
  2019-08-07 22:43 ` [PATCH v4 QEMU 2/3] virtio-balloon: Add bit to notify guest of unused page reporting Alexander Duyck
  2019-08-07 22:43 ` [PATCH v4 QEMU 3/3] virtio-balloon: Provide a interface for " Alexander Duyck
  8 siblings, 0 replies; 17+ messages in thread
From: Alexander Duyck @ 2019-08-07 22:43 UTC (permalink / raw)
  To: nitesh, kvm, david, mst, dave.hansen, linux-kernel, linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

We need to make certain to advertise support for page poison tracking if
we want to actually get data on if the guest will be poisoning pages. So
if free page hinting is active we should add page poisoning support and
let the guest disable it if it isn't using it.

Page poisoning will result in a page being dirtied on free. As such we
cannot really avoid having to copy the page at least one more time since
we will need to write the poison value to the destination. As such we can
just ignore free page hinting if page poisoning is enabled as it will
actually reduce the work we have to do.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 hw/virtio/virtio-balloon.c         |   25 +++++++++++++++++++++----
 include/hw/virtio/virtio-balloon.h |    1 +
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 25de15430710..003b3ebcfdfb 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -530,6 +530,15 @@ static void virtio_balloon_free_page_start(VirtIOBalloon *s)
         return;
     }
 
+    /*
+     * If page poisoning is enabled then we probably shouldn't bother with
+     * the hinting since the poisoning will dirty the page and invalidate
+     * the work we are doing anyway.
+     */
+    if (virtio_vdev_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
+        return;
+    }
+
     if (s->free_page_report_cmd_id == UINT_MAX) {
         s->free_page_report_cmd_id =
                        VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN;
@@ -617,12 +626,10 @@ static size_t virtio_balloon_config_size(VirtIOBalloon *s)
     if (s->qemu_4_0_config_size) {
         return sizeof(struct virtio_balloon_config);
     }
-    if (virtio_has_feature(features, VIRTIO_BALLOON_F_PAGE_POISON)) {
+    if (virtio_has_feature(features, VIRTIO_BALLOON_F_PAGE_POISON) ||
+        virtio_has_feature(features, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
         return sizeof(struct virtio_balloon_config);
     }
-    if (virtio_has_feature(features, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
-        return offsetof(struct virtio_balloon_config, poison_val);
-    }
     return offsetof(struct virtio_balloon_config, free_page_report_cmd_id);
 }
 
@@ -633,6 +640,7 @@ static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
 
     config.num_pages = cpu_to_le32(dev->num_pages);
     config.actual = cpu_to_le32(dev->actual);
+    config.poison_val = cpu_to_le32(dev->poison_val);
 
     if (dev->free_page_report_status == FREE_PAGE_REPORT_S_REQUESTED) {
         config.free_page_report_cmd_id =
@@ -696,6 +704,8 @@ static void virtio_balloon_set_config(VirtIODevice *vdev,
         qapi_event_send_balloon_change(vm_ram_size -
                         ((ram_addr_t) dev->actual << VIRTIO_BALLOON_PFN_SHIFT));
     }
+    dev->poison_val = virtio_vdev_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON) ? 
+                      le32_to_cpu(config.poison_val) : 0;
     trace_virtio_balloon_set_config(dev->actual, oldactual);
 }
 
@@ -705,6 +715,9 @@ static uint64_t virtio_balloon_get_features(VirtIODevice *vdev, uint64_t f,
     VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
     f |= dev->host_features;
     virtio_add_feature(&f, VIRTIO_BALLOON_F_STATS_VQ);
+    if (virtio_has_feature(f, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
+        virtio_add_feature(&f, VIRTIO_BALLOON_F_PAGE_POISON);
+    }
 
     return f;
 }
@@ -846,6 +859,8 @@ static void virtio_balloon_device_reset(VirtIODevice *vdev)
         g_free(s->stats_vq_elem);
         s->stats_vq_elem = NULL;
     }
+
+    s->poison_val = 0;
 }
 
 static void virtio_balloon_set_status(VirtIODevice *vdev, uint8_t status)
@@ -908,6 +923,8 @@ static Property virtio_balloon_properties[] = {
                     VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false),
     DEFINE_PROP_BIT("free-page-hint", VirtIOBalloon, host_features,
                     VIRTIO_BALLOON_F_FREE_PAGE_HINT, false),
+    DEFINE_PROP_BIT("x-page-poison", VirtIOBalloon, host_features,
+                    VIRTIO_BALLOON_F_PAGE_POISON, false),
     /* QEMU 4.0 accidentally changed the config size even when free-page-hint
      * is disabled, resulting in QEMU 3.1 migration incompatibility.  This
      * property retains this quirk for QEMU 4.1 machine types.
diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
index d1c968d2376e..7fe78e5c14d7 100644
--- a/include/hw/virtio/virtio-balloon.h
+++ b/include/hw/virtio/virtio-balloon.h
@@ -70,6 +70,7 @@ typedef struct VirtIOBalloon {
     uint32_t host_features;
 
     bool qemu_4_0_config_size;
+    uint32_t poison_val;
 } VirtIOBalloon;
 
 #endif


^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v4 QEMU 2/3] virtio-balloon: Add bit to notify guest of unused page reporting
  2019-08-07 22:41 [PATCH v4 0/6] mm / virtio: Provide support for unused page reporting Alexander Duyck
                   ` (6 preceding siblings ...)
  2019-08-07 22:43 ` [PATCH v4 QEMU 1/3] virtio-ballon: Implement support for page poison tracking feature Alexander Duyck
@ 2019-08-07 22:43 ` Alexander Duyck
  2019-08-07 22:43 ` [PATCH v4 QEMU 3/3] virtio-balloon: Provide a interface for " Alexander Duyck
  8 siblings, 0 replies; 17+ messages in thread
From: Alexander Duyck @ 2019-08-07 22:43 UTC (permalink / raw)
  To: nitesh, kvm, david, mst, dave.hansen, linux-kernel, linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

Add a bit for the page reporting feature provided by virtio-balloon.

This patch should be replaced once the feature is added to the Linux kernel
and the bit is backported into this exported kernel header.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 include/standard-headers/linux/virtio_balloon.h |    1 +
 1 file changed, 1 insertion(+)

diff --git a/include/standard-headers/linux/virtio_balloon.h b/include/standard-headers/linux/virtio_balloon.h
index 9375ca2a70de..1c5f6d6f2de6 100644
--- a/include/standard-headers/linux/virtio_balloon.h
+++ b/include/standard-headers/linux/virtio_balloon.h
@@ -36,6 +36,7 @@
 #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */
 #define VIRTIO_BALLOON_F_FREE_PAGE_HINT	3 /* VQ to report free pages */
 #define VIRTIO_BALLOON_F_PAGE_POISON	4 /* Guest is using page poisoning */
+#define VIRTIO_BALLOON_F_REPORTING	5 /* Page reporting virtqueue */
 
 /* Size of a PFN in the balloon interface. */
 #define VIRTIO_BALLOON_PFN_SHIFT 12


^ permalink raw reply	[flat|nested] 17+ messages in thread

* [PATCH v4 QEMU 3/3] virtio-balloon: Provide a interface for unused page reporting
  2019-08-07 22:41 [PATCH v4 0/6] mm / virtio: Provide support for unused page reporting Alexander Duyck
                   ` (7 preceding siblings ...)
  2019-08-07 22:43 ` [PATCH v4 QEMU 2/3] virtio-balloon: Add bit to notify guest of unused page reporting Alexander Duyck
@ 2019-08-07 22:43 ` " Alexander Duyck
  8 siblings, 0 replies; 17+ messages in thread
From: Alexander Duyck @ 2019-08-07 22:43 UTC (permalink / raw)
  To: nitesh, kvm, david, mst, dave.hansen, linux-kernel, linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

Add support for what I am referring to as "unused page reporting".
Basically the idea is to function very similar to how the balloon works
in that we basically end up madvising the page as not being used. However
we don't really need to bother with any deflate type logic since the page
will be faulted back into the guest when it is read or written to.

This is meant to be a simplification of the existing balloon interface
to use for providing hints to what memory needs to be freed. I am assuming
this is safe to do as the deflate logic does not actually appear to do very
much other than tracking what subpages have been released and which ones
haven't.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 hw/virtio/virtio-balloon.c         |   46 ++++++++++++++++++++++++++++++++++--
 include/hw/virtio/virtio-balloon.h |    2 +-
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 003b3ebcfdfb..7a30df63bc77 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -320,6 +320,40 @@ static void balloon_stats_set_poll_interval(Object *obj, Visitor *v,
     balloon_stats_change_timer(s, 0);
 }
 
+static void virtio_balloon_handle_report(VirtIODevice *vdev, VirtQueue *vq)
+{
+    VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
+    VirtQueueElement *elem;
+
+    while ((elem = virtqueue_pop(vq, sizeof(VirtQueueElement)))) {
+    	unsigned int i;
+
+        for (i = 0; i < elem->in_num; i++) {
+            void *addr = elem->in_sg[i].iov_base;
+            size_t size = elem->in_sg[i].iov_len;
+            ram_addr_t ram_offset;
+            size_t rb_page_size;
+            RAMBlock *rb;
+
+            if (qemu_balloon_is_inhibited() || dev->poison_val)
+                continue;
+
+            rb = qemu_ram_block_from_host(addr, false, &ram_offset);
+            rb_page_size = qemu_ram_pagesize(rb);
+
+            /* For now we will simply ignore unaligned memory regions */
+            if ((ram_offset | size) & (rb_page_size - 1))
+                continue;
+
+            ram_block_discard_range(rb, ram_offset, size);
+        }
+
+        virtqueue_push(vq, elem, 0);
+        virtio_notify(vdev, vq);
+        g_free(elem);
+    }
+}
+
 static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
 {
     VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
@@ -627,7 +661,8 @@ static size_t virtio_balloon_config_size(VirtIOBalloon *s)
         return sizeof(struct virtio_balloon_config);
     }
     if (virtio_has_feature(features, VIRTIO_BALLOON_F_PAGE_POISON) ||
-        virtio_has_feature(features, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
+        virtio_has_feature(features, VIRTIO_BALLOON_F_FREE_PAGE_HINT) ||
+        virtio_has_feature(features, VIRTIO_BALLOON_F_REPORTING)) {
         return sizeof(struct virtio_balloon_config);
     }
     return offsetof(struct virtio_balloon_config, free_page_report_cmd_id);
@@ -715,7 +750,8 @@ static uint64_t virtio_balloon_get_features(VirtIODevice *vdev, uint64_t f,
     VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
     f |= dev->host_features;
     virtio_add_feature(&f, VIRTIO_BALLOON_F_STATS_VQ);
-    if (virtio_has_feature(f, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
+    if (virtio_has_feature(f, VIRTIO_BALLOON_F_FREE_PAGE_HINT) ||
+        virtio_has_feature(f, VIRTIO_BALLOON_F_REPORTING)) {
         virtio_add_feature(&f, VIRTIO_BALLOON_F_PAGE_POISON);
     }
 
@@ -805,6 +841,10 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
     s->dvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
     s->svq = virtio_add_queue(vdev, 128, virtio_balloon_receive_stats);
 
+    if (virtio_has_feature(s->host_features, VIRTIO_BALLOON_F_REPORTING)) {
+        s->rvq = virtio_add_queue(vdev, 32, virtio_balloon_handle_report);
+    }
+
     if (virtio_has_feature(s->host_features,
                            VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
         s->free_page_vq = virtio_add_queue(vdev, VIRTQUEUE_MAX_SIZE,
@@ -931,6 +971,8 @@ static Property virtio_balloon_properties[] = {
      */
     DEFINE_PROP_BOOL("qemu-4-0-config-size", VirtIOBalloon,
                      qemu_4_0_config_size, false),
+    DEFINE_PROP_BIT("unused-page-reporting", VirtIOBalloon, host_features,
+                    VIRTIO_BALLOON_F_REPORTING, true),
     DEFINE_PROP_LINK("iothread", VirtIOBalloon, iothread, TYPE_IOTHREAD,
                      IOThread *),
     DEFINE_PROP_END_OF_LIST(),
diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
index 7fe78e5c14d7..db5bf7127112 100644
--- a/include/hw/virtio/virtio-balloon.h
+++ b/include/hw/virtio/virtio-balloon.h
@@ -42,7 +42,7 @@ enum virtio_balloon_free_page_report_status {
 
 typedef struct VirtIOBalloon {
     VirtIODevice parent_obj;
-    VirtQueue *ivq, *dvq, *svq, *free_page_vq;
+    VirtQueue *ivq, *dvq, *svq, *free_page_vq, *rvq;
     uint32_t free_page_report_status;
     uint32_t num_pages;
     uint32_t actual;


^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v4 4/6] mm: Introduce Reported pages
  2019-08-07 22:42 ` [PATCH v4 4/6] mm: Introduce Reported pages Alexander Duyck
@ 2019-08-08 13:45   ` Nitesh Narayan Lal
  2019-08-08 15:11     ` Alexander Duyck
  0 siblings, 1 reply; 17+ messages in thread
From: Nitesh Narayan Lal @ 2019-08-08 13:45 UTC (permalink / raw)
  To: Alexander Duyck, kvm, david, mst, dave.hansen, linux-kernel,
	linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck


On 8/7/19 6:42 PM, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
>
> In order to pave the way for free page reporting in virtualized
> environments we will need a way to get pages out of the free lists and
> identify those pages after they have been returned. To accomplish this,
> this patch adds the concept of a Reported Buddy, which is essentially
> meant to just be the Uptodate flag used in conjunction with the Buddy
> page type.
>
> It adds a set of pointers we shall call "boundary" which represents the
> upper boundary between the unreported and reported pages. The general idea
> is that in order for a page to cross from one side of the boundary to the
> other it will need to go through the reporting process. Ultimately a
> free_list has been fully processed when the boundary has been moved from
> the tail all they way up to occupying the first entry in the list.
>
> Doing this we should be able to make certain that we keep the reported
> pages as one contiguous block in each free list. This will allow us to
> efficiently manipulate the free lists whenever we need to go in and start
> sending reports to the hypervisor that there are new pages that have been
> freed and are no longer in use.
>
> An added advantage to this approach is that we should be reducing the
> overall memory footprint of the guest as it will be more likely to recycle
> warm pages versus trying to allocate the reported pages that were likely
> evicted from the guest memory.
>
> Since we will only be reporting one zone at a time we keep the boundary
> limited to being defined for just the zone we are currently reporting pages
> from. Doing this we can keep the number of additional pointers needed quite
> small. To flag that the boundaries are in place we use a single bit
> in the zone to indicate that reporting and the boundaries are active.
>
> The determination of when to start reporting is based on the tracking of
> the number of free pages in a given area versus the number of reported
> pages in that area. We keep track of the number of reported pages per
> free_area in a separate zone specific area. We do this to avoid modifying
> the free_area structure as this can lead to false sharing for the highest
> order with the zone lock which leads to a noticeable performance
> degradation.
>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> ---
>  include/linux/mmzone.h         |   40 +++++
>  include/linux/page-flags.h     |   11 +
>  include/linux/page_reporting.h |  138 ++++++++++++++++++
>  mm/Kconfig                     |    5 +
>  mm/Makefile                    |    1 
>  mm/memory_hotplug.c            |    1 
>  mm/page_alloc.c                |  136 +++++++++++++++++
>  mm/page_reporting.c            |  313 ++++++++++++++++++++++++++++++++++++++++
>  8 files changed, 637 insertions(+), 8 deletions(-)
>  create mode 100644 include/linux/page_reporting.h
>  create mode 100644 mm/page_reporting.c
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 2f2b6f968ed3..b8ed926552b1 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -462,6 +462,14 @@ struct zone {
>  	seqlock_t		span_seqlock;
>  #endif
>  
> +#ifdef CONFIG_PAGE_REPORTING
> +	/*
> +	 * Pointer to reported page tracking statistics array. The size of
> +	 * the array is MAX_ORDER - PAGE_REPORTING_MIN_ORDER. NULL when
> +	 * unused page reporting is not present.
> +	 */
> +	unsigned long		*reported_pages;
> +#endif
>  	int initialized;
>  
>  	/* Write-intensive fields used from the page allocator */
> @@ -537,6 +545,14 @@ enum zone_flags {
>  	ZONE_BOOSTED_WATERMARK,		/* zone recently boosted watermarks.
>  					 * Cleared when kswapd is woken.
>  					 */
> +	ZONE_PAGE_REPORTING_REQUESTED,	/* zone enabled page reporting and has
> +					 * requested flushing the data out of
> +					 * higher order pages.
> +					 */
> +	ZONE_PAGE_REPORTING_ACTIVE,	/* zone enabled page reporting and is
> +					 * activly flushing the data out of
> +					 * higher order pages.
> +					 */
>  };
>  
>  static inline unsigned long zone_managed_pages(struct zone *zone)
> @@ -757,6 +773,8 @@ static inline bool pgdat_is_empty(pg_data_t *pgdat)
>  	return !pgdat->node_start_pfn && !pgdat->node_spanned_pages;
>  }
>  
> +#include <linux/page_reporting.h>
> +
>  /* Used for pages not on another list */
>  static inline void add_to_free_list(struct page *page, struct zone *zone,
>  				    unsigned int order, int migratetype)
> @@ -771,10 +789,16 @@ static inline void add_to_free_list(struct page *page, struct zone *zone,
>  static inline void add_to_free_list_tail(struct page *page, struct zone *zone,
>  					 unsigned int order, int migratetype)
>  {
> -	struct free_area *area = &zone->free_area[order];
> +	struct list_head *tail = get_unreported_tail(zone, order, migratetype);
>  
> -	list_add_tail(&page->lru, &area->free_list[migratetype]);
> -	area->nr_free++;
> +	/*
> +	 * To prevent the unreported pages from being interleaved with the
> +	 * reported ones while we are actively processing pages we will use
> +	 * the head of the reported pages to determine the tail of the free
> +	 * list.
> +	 */
> +	list_add_tail(&page->lru, tail);
> +	zone->free_area[order].nr_free++;
>  }
>  
>  /* Used for pages which are on another list */
> @@ -783,12 +807,22 @@ static inline void move_to_free_list(struct page *page, struct zone *zone,
>  {
>  	struct free_area *area = &zone->free_area[order];
>  
> +	/*
> +	 * Clear Hinted flag, if present, to avoid placing reported pages
> +	 * at the top of the free_list. It is cheaper to just process this
> +	 * page again than to walk around a page that is already reported.
> +	 */
> +	clear_page_reported(page, zone);
> +
>  	list_move(&page->lru, &area->free_list[migratetype]);
>  }
>  
>  static inline void del_page_from_free_list(struct page *page, struct zone *zone,
>  					   unsigned int order)
>  {
> +	/* Clear Reported flag, if present, before resetting page type */
> +	clear_page_reported(page, zone);
> +
>  	list_del(&page->lru);
>  	__ClearPageBuddy(page);
>  	set_page_private(page, 0);
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index f91cb8898ff0..759a3b3956f2 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -163,6 +163,9 @@ enum pageflags {
>  
>  	/* non-lru isolated movable page */
>  	PG_isolated = PG_reclaim,
> +
> +	/* Buddy pages. Used to track which pages have been reported */
> +	PG_reported = PG_uptodate,
>  };
>  
>  #ifndef __GENERATING_BOUNDS_H
> @@ -432,6 +435,14 @@ static inline bool set_hwpoison_free_buddy_page(struct page *page)
>  #endif
>  
>  /*
> + * PageReported() is used to track reported free pages within the Buddy
> + * allocator. We can use the non-atomic version of the test and set
> + * operations as both should be shielded with the zone lock to prevent
> + * any possible races on the setting or clearing of the bit.
> + */
> +__PAGEFLAG(Reported, reported, PF_NO_COMPOUND)
> +
> +/*
>   * On an anonymous page mapped into a user virtual memory area,
>   * page->mapping points to its anon_vma, not to a struct address_space;
>   * with the PAGE_MAPPING_ANON bit set to distinguish it.  See rmap.h.
> diff --git a/include/linux/page_reporting.h b/include/linux/page_reporting.h
> new file mode 100644
> index 000000000000..498bde6ea764
> --- /dev/null
> +++ b/include/linux/page_reporting.h
> @@ -0,0 +1,138 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _LINUX_PAGE_REPORTING_H
> +#define _LINUX_PAGE_REPORTING_H
> +
> +#include <linux/mmzone.h>
> +#include <linux/jump_label.h>
> +#include <linux/pageblock-flags.h>
> +#include <asm/pgtable_types.h>
> +
> +#define PAGE_REPORTING_MIN_ORDER	pageblock_order
> +#define PAGE_REPORTING_HWM		32
> +
> +#ifdef CONFIG_PAGE_REPORTING
> +struct page_reporting_dev_info {
> +	/* function that alters pages to make them "reported" */
> +	void (*report)(struct page_reporting_dev_info *phdev,
> +		       unsigned int nents);
> +
> +	/* scatterlist containing pages to be processed */
> +	struct scatterlist *sg;
> +
> +	/*
> +	 * Upper limit on the number of pages that the react function
> +	 * expects to be placed into the batch list to be processed.
> +	 */
> +	unsigned long capacity;
> +
> +	/* work struct for processing reports */
> +	struct delayed_work work;
> +
> +	/*
> +	 * The number of zones requesting reporting, plus one additional if
> +	 * processing thread is active.
> +	 */
> +	atomic_t refcnt;
> +};
> +
> +extern struct static_key page_reporting_notify_enabled;
> +
> +/* Boundary functions */
> +struct list_head *__page_reporting_get_boundary(unsigned int order,
> +						int migratetype);
> +void page_reporting_del_from_boundary(struct page *page, struct zone *zone);
> +void page_reporting_add_to_boundary(struct page *page, struct zone *zone,
> +				    int migratetype);
> +
> +/* Hinted page accessors, defined in page_alloc.c */
> +struct page *get_unreported_page(struct zone *zone, unsigned int order,
> +				 int migratetype);
> +void put_reported_page(struct zone *zone, struct page *page);
> +
> +void __page_reporting_request(struct zone *zone);
> +void __page_reporting_free_stats(struct zone *zone);
> +
> +/* Tear-down and bring-up for page reporting devices */
> +void page_reporting_shutdown(struct page_reporting_dev_info *phdev);
> +int page_reporting_startup(struct page_reporting_dev_info *phdev);
> +#endif /* CONFIG_PAGE_REPORTING */
> +
> +static inline struct list_head *
> +get_unreported_tail(struct zone *zone, unsigned int order, int migratetype)
> +{
> +#ifdef CONFIG_PAGE_REPORTING
> +	if (order >= PAGE_REPORTING_MIN_ORDER &&
> +	    test_bit(ZONE_PAGE_REPORTING_ACTIVE, &zone->flags))
> +		return __page_reporting_get_boundary(order, migratetype);
> +#endif
> +	return &zone->free_area[order].free_list[migratetype];
> +}
> +
> +static inline void clear_page_reported(struct page *page,
> +				     struct zone *zone)
> +{
> +#ifdef CONFIG_PAGE_REPORTING
> +	if (likely(!PageReported(page)))
> +		return;
> +
> +	/* push boundary back if we removed the upper boundary */
> +	if (test_bit(ZONE_PAGE_REPORTING_ACTIVE, &zone->flags))
> +		page_reporting_del_from_boundary(page, zone);
> +
> +	__ClearPageReported(page);
> +
> +	/* page_private will contain the page order, so just use it directly */
> +	zone->reported_pages[page_private(page) - PAGE_REPORTING_MIN_ORDER]--;
> +#endif
> +}
> +
> +/* Free reported_pages and reset reported page tracking count to 0 */
> +static inline void page_reporting_reset(struct zone *zone)
> +{
> +#ifdef CONFIG_PAGE_REPORTING
> +	if (zone->reported_pages)
> +		__page_reporting_free_stats(zone);
> +#endif
> +}
> +
> +/**
> + * page_reporting_notify_free - Free page notification to start page processing
> + * @zone: Pointer to current zone of last page processed
> + * @order: Order of last page added to zone
> + *
> + * This function is meant to act as a screener for __page_reporting_request
> + * which will determine if a give zone has crossed over the high-water mark
> + * that will justify us beginning page treatment. If we have crossed that
> + * threshold then it will start the process of pulling some pages and
> + * placing them in the batch list for treatment.
> + */
> +static inline void page_reporting_notify_free(struct zone *zone, int order)
> +{
> +#ifdef CONFIG_PAGE_REPORTING
> +	unsigned long nr_reported;
> +
> +	/* Called from hot path in __free_one_page() */
> +	if (!static_key_false(&page_reporting_notify_enabled))
> +		return;
> +
> +	/* Limit notifications only to higher order pages */
> +	if (order < PAGE_REPORTING_MIN_ORDER)
> +		return;
> +
> +	/* Do not bother with tests if we have already requested reporting */
> +	if (test_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags))
> +		return;
> +
> +	/* If reported_pages is not populated, assume 0 */
> +	nr_reported = zone->reported_pages ?
> +		    zone->reported_pages[order - PAGE_REPORTING_MIN_ORDER] : 0;
> +
> +	/* Only request it if we have enough to begin the page reporting */
> +	if (zone->free_area[order].nr_free < nr_reported + PAGE_REPORTING_HWM)
> +		return;
> +
> +	/* This is slow, but should be called very rarely */
> +	__page_reporting_request(zone);
> +#endif
> +}
> +#endif /*_LINUX_PAGE_REPORTING_H */
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 06f758786e4a..52c6c49f0f69 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -237,6 +237,11 @@ config COMPACTION
>            linux-mm@kvack.org.
>  
>  #
> +# support for unused page reporting
> +config PAGE_REPORTING
> +	bool
> +
> +#
>  # support for page migration
>  #
>  config MIGRATION
> diff --git a/mm/Makefile b/mm/Makefile
> index d0b295c3b764..1e17ba0ed2f0 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -105,3 +105,4 @@ obj-$(CONFIG_PERCPU_STATS) += percpu-stats.o
>  obj-$(CONFIG_ZONE_DEVICE) += memremap.o
>  obj-$(CONFIG_HMM_MIRROR) += hmm.o
>  obj-$(CONFIG_MEMFD_CREATE) += memfd.o
> +obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 5b8811945bbb..bd40beac293b 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1612,6 +1612,7 @@ static int __ref __offline_pages(unsigned long start_pfn,
>  	if (!populated_zone(zone)) {
>  		zone_pcp_reset(zone);
>  		build_all_zonelists(NULL);
> +		page_reporting_reset(zone);
>  	} else
>  		zone_pcp_update(zone);
>  
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 4b5812c3800e..d0d3fb12ba54 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -68,6 +68,7 @@
>  #include <linux/lockdep.h>
>  #include <linux/nmi.h>
>  #include <linux/psi.h>
> +#include <linux/page_reporting.h>
>  
>  #include <asm/sections.h>
>  #include <asm/tlbflush.h>
> @@ -915,7 +916,7 @@ static inline struct capture_control *task_capc(struct zone *zone)
>  static inline void __free_one_page(struct page *page,
>  		unsigned long pfn,
>  		struct zone *zone, unsigned int order,
> -		int migratetype)
> +		int migratetype, bool reported)
>  {
>  	struct capture_control *capc = task_capc(zone);
>  	unsigned long uninitialized_var(buddy_pfn);
> @@ -990,11 +991,20 @@ static inline void __free_one_page(struct page *page,
>  done_merging:
>  	set_page_order(page, order);
>  
> -	if (is_shuffle_order(order) ? shuffle_add_to_tail() :
> -	    buddy_merge_likely(pfn, buddy_pfn, page, order))
> +	if (reported ||
> +	    (is_shuffle_order(order) ? shuffle_add_to_tail() :
> +	     buddy_merge_likely(pfn, buddy_pfn, page, order)))
>  		add_to_free_list_tail(page, zone, order, migratetype);
>  	else
>  		add_to_free_list(page, zone, order, migratetype);
> +
> +	/*
> +	 * No need to notify on a reported page as the total count of
> +	 * unreported pages will not have increased since we have essentially
> +	 * merged the reported page with one or more unreported pages.
> +	 */
> +	if (!reported)
> +		page_reporting_notify_free(zone, order);
>  }
>  
>  /*
> @@ -1305,7 +1315,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
>  		if (unlikely(isolated_pageblocks))
>  			mt = get_pageblock_migratetype(page);
>  
> -		__free_one_page(page, page_to_pfn(page), zone, 0, mt);
> +		__free_one_page(page, page_to_pfn(page), zone, 0, mt, false);
>  		trace_mm_page_pcpu_drain(page, 0, mt);
>  	}
>  	spin_unlock(&zone->lock);
> @@ -1321,7 +1331,7 @@ static void free_one_page(struct zone *zone,
>  		is_migrate_isolate(migratetype))) {
>  		migratetype = get_pfnblock_migratetype(page, pfn);
>  	}
> -	__free_one_page(page, pfn, zone, order, migratetype);
> +	__free_one_page(page, pfn, zone, order, migratetype, false);
>  	spin_unlock(&zone->lock);
>  }
>  
> @@ -2183,6 +2193,122 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
>  	return NULL;
>  }
>  
> +#ifdef CONFIG_PAGE_REPORTING
> +/**
> + * get_unreported_page - Pull an unreported page from the free_list
> + * @zone: Zone to draw pages from
> + * @order: Order to draw pages from
> + * @mt: Migratetype to draw pages from
> + *
> + * This function will obtain a page from the free list. It will start by
> + * attempting to pull from the tail of the free list and if that is already
> + * reported on it will instead pull the head if that is unreported.
> + *
> + * The page will have the migrate type and order stored in the page
> + * metadata. While being processed the page will not be avaialble for
> + * allocation.
> + *
> + * Return: page pointer if raw page found, otherwise NULL
> + */
> +struct page *get_unreported_page(struct zone *zone, unsigned int order, int mt)
> +{
> +	struct list_head *tail = get_unreported_tail(zone, order, mt);
> +	struct free_area *area = &(zone->free_area[order]);
> +	struct list_head *list = &area->free_list[mt];
> +	struct page *page;
> +
> +	/* zone lock should be held when this function is called */
> +	lockdep_assert_held(&zone->lock);
> +
> +	/* Find a page of the appropriate size in the preferred list */
> +	page = list_last_entry(tail, struct page, lru);
> +	list_for_each_entry_from_reverse(page, list, lru) {
> +		/* If we entered this loop then the "raw" list isn't empty */
> +
> +		/* If the page is reported try the head of the list */
> +		if (PageReported(page)) {
> +			page = list_first_entry(list, struct page, lru);
> +
> +			/*
> +			 * If both the head and tail are reported then reset
> +			 * the boundary so that we read as an empty list
> +			 * next time and bail out.
> +			 */
> +			if (PageReported(page)) {
> +				page_reporting_add_to_boundary(page, zone, mt);
> +				break;
> +			}
> +		}
> +
> +		del_page_from_free_list(page, zone, order);
> +
> +		/* record migratetype and order within page */
> +		set_pcppage_migratetype(page, mt);
> +		set_page_private(page, order);
> +
> +		/*
> +		 * Page will not be available for allocation while we are
> +		 * processing it so update the freepage state.
> +		 */
> +		__mod_zone_freepage_state(zone, -(1 << order), mt);
> +
> +		return page;
> +	}
> +
> +	return NULL;
> +}
> +
> +/**
> + * put_reported_page - Return a now-reported page back where we got it
> + * @zone: Zone to return pages to
> + * @page: Page that was reported
> + *
> + * This function will pull the migratetype and order information out
> + * of the page and attempt to return it where it found it. If the page
> + * is added to the free list without changes we will mark it as being
> + * reported.
> + */
> +void put_reported_page(struct zone *zone, struct page *page)
> +{
> +	unsigned int order, mt;
> +	unsigned long pfn;
> +
> +	/* zone lock should be held when this function is called */
> +	lockdep_assert_held(&zone->lock);
> +
> +	mt = get_pcppage_migratetype(page);
> +	pfn = page_to_pfn(page);
> +
> +	if (unlikely(has_isolate_pageblock(zone) || is_migrate_isolate(mt))) {
> +		mt = get_pfnblock_migratetype(page, pfn);
> +		set_pcppage_migratetype(page, mt);
> +	}
> +
> +	order = page_private(page);
> +	set_page_private(page, 0);
> +
> +	__free_one_page(page, pfn, zone, order, mt, true);
> +
> +	/*
> +	 * If page was comingled with another page we cannot consider
> +	 * the result to be "reported" since part of the page hasn't been.
> +	 * In this case we will simply exit and not update the "reported"
> +	 * state. Instead just treat the result as a unreported page.
> +	 */
> +	if (!PageBuddy(page) || page_order(page) != order)
> +		return;
> +
> +	/* update areated page accounting */
> +	zone->reported_pages[order - PAGE_REPORTING_MIN_ORDER]++;
> +
> +	/* update boundary of new migratetype and record it */
> +	page_reporting_add_to_boundary(page, zone, mt);
> +
> +	/* flag page as reported */
> +	__SetPageReported(page);
> +}
> +#endif /* CONFIG_PAGE_REPORTING */
> +
>  /*
>   * This array describes the order lists are fallen back to when
>   * the free lists for the desirable migrate type are depleted
> diff --git a/mm/page_reporting.c b/mm/page_reporting.c
> new file mode 100644
> index 000000000000..ae26dd77bce9
> --- /dev/null
> +++ b/mm/page_reporting.c
> @@ -0,0 +1,313 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/mm.h>
> +#include <linux/mmzone.h>
> +#include <linux/page-isolation.h>
> +#include <linux/gfp.h>
> +#include <linux/export.h>
> +#include <linux/delay.h>
> +#include <linux/slab.h>
> +#include <linux/scatterlist.h>
> +#include "internal.h"
> +
> +static struct page_reporting_dev_info __rcu *ph_dev_info __read_mostly;
> +struct static_key page_reporting_notify_enabled;
> +
> +struct list_head *boundary[MAX_ORDER - PAGE_REPORTING_MIN_ORDER][MIGRATE_TYPES];
> +
> +static void page_reporting_reset_boundary(struct zone *zone, unsigned int order,
> +					  unsigned int migratetype)
> +{
> +	boundary[order - PAGE_REPORTING_MIN_ORDER][migratetype] =
> +			&zone->free_area[order].free_list[migratetype];
> +}
> +
> +#define for_each_reporting_migratetype_order(_order, _type) \
> +	for (_order = MAX_ORDER; _order-- != PAGE_REPORTING_MIN_ORDER;) \
> +		for (_type = MIGRATE_TYPES; _type--;)
> +
> +static int page_reporting_populate_metadata(struct zone *zone)
> +{
> +	unsigned int order, mt;
> +
> +	/*
> +	 * We need to make sure we have somewhere to store the tracking
> +	 * data for how many reported pages are in the zone. To do that
> +	 * we need to make certain zone->reported_pages is populated.
> +	 */
> +	if (!zone->reported_pages) {
> +		zone->reported_pages =
> +			kcalloc(MAX_ORDER - PAGE_REPORTING_MIN_ORDER,
> +				sizeof(unsigned long),
> +				GFP_KERNEL);
> +		if (!zone->reported_pages)
> +			return -ENOMEM;
> +	}
> +
> +	/* Update boundary data to reflect the zone we are currently working */
> +	for_each_reporting_migratetype_order(order, mt)
> +		page_reporting_reset_boundary(zone, order, mt);
> +
> +	return 0;
> +}
> +
> +struct list_head *__page_reporting_get_boundary(unsigned int order,
> +						int migratetype)
> +{
> +	return boundary[order - PAGE_REPORTING_MIN_ORDER][migratetype];
> +}
> +
> +void page_reporting_del_from_boundary(struct page *page, struct zone *zone)
> +{
> +	unsigned int order = page_private(page) - PAGE_REPORTING_MIN_ORDER;
> +	int mt = get_pcppage_migratetype(page);
> +	struct list_head **tail = &boundary[order][mt];
> +
> +	if (*tail == &page->lru)
> +		*tail = page->lru.next;
> +}
> +
> +void page_reporting_add_to_boundary(struct page *page, struct zone *zone,
> +				    int migratetype)
> +{
> +	unsigned int order = page_private(page) - PAGE_REPORTING_MIN_ORDER;
> +	struct list_head **tail = &boundary[order][migratetype];
> +
> +	*tail = &page->lru;
> +}
> +
> +static unsigned int page_reporting_fill(struct zone *zone,
> +					struct page_reporting_dev_info *phdev)
> +{
> +	struct scatterlist *sg = phdev->sg;
> +	unsigned int order, mt, count = 0;
> +
> +	sg_init_table(phdev->sg, phdev->capacity);
> +
> +	for_each_reporting_migratetype_order(order, mt) {
> +		struct page *page;
> +
> +		/*
> +		 * Pull pages from free list until we have drained
> +		 * it or we have reached capacity.
> +		 */
> +		while ((page = get_unreported_page(zone, order, mt))) {
> +			sg_set_page(&sg[count], page, PAGE_SIZE << order, 0);
> +
> +			if (++count == phdev->capacity)
> +				return count;
> +		}
> +	}
> +
> +	/* mark end of scatterlist due to underflow */
> +	if (count)
> +		sg_mark_end(&sg[count - 1]);
> +
> +	/*
> +	 * If there are no longer enough free pages to fully populate
> +	 * the scatterlist, then we can just shut it down for this zone.
> +	 */
> +	__clear_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags);
> +	atomic_dec(&phdev->refcnt);
> +
> +	return count;
> +}
> +
> +static void page_reporting_drain(struct zone *zone,
> +				 struct page_reporting_dev_info *phdev)
> +{
> +	struct scatterlist *sg = phdev->sg;
> +
> +	/*
> +	 * Drain the now reported pages back into their respective
> +	 * free lists/areas. We assume at least one page is populated.
> +	 */
> +	do {
> +		put_reported_page(zone, sg_page(sg));
> +	} while (!sg_is_last(sg++));
> +}
> +
> +/*
> + * The page reporting cycle consists of 4 stages, fill, report, drain, and idle.
> + * We will cycle through the first 3 stages until we fail to obtain any
> + * pages, in that case we will switch to idle.
> + */
> +static void page_reporting_cycle(struct zone *zone,
> +				 struct page_reporting_dev_info *phdev)
> +{
> +	/*
> +	 * Guarantee boundaries and stats are populated before we
> +	 * start placing reported pages in the zone.
> +	 */
> +	if (page_reporting_populate_metadata(zone))
> +		return;
> +
> +	spin_lock(&zone->lock);
> +
> +	/* set bit indicating boundaries are present */
> +	__set_bit(ZONE_PAGE_REPORTING_ACTIVE, &zone->flags);
> +
> +	do {
> +		/* Pull pages out of allocator into a scaterlist */
> +		unsigned int nents = page_reporting_fill(zone, phdev);
> +
> +		/* no pages were acquired, give up */
> +		if (!nents)
> +			break;
> +
> +		spin_unlock(&zone->lock);
> +
> +		/* begin processing pages in local list */
> +		phdev->report(phdev, nents);
> +
> +		spin_lock(&zone->lock);
> +
> +		/*
> +		 * We should have a scatterlist of pages that have been
> +		 * processed. Return them to their original free lists.
> +		 */
> +		page_reporting_drain(zone, phdev);
> +
> +		/* keep pulling pages till there are none to pull */
> +	} while (test_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags));
> +
> +	/* processing of the zone is complete, we can disable boundaries */
> +	__clear_bit(ZONE_PAGE_REPORTING_ACTIVE, &zone->flags);
> +
> +	spin_unlock(&zone->lock);
> +}
> +
> +static void page_reporting_process(struct work_struct *work)
> +{
> +	struct delayed_work *d_work = to_delayed_work(work);
> +	struct page_reporting_dev_info *phdev =
> +		container_of(d_work, struct page_reporting_dev_info, work);
> +	struct zone *zone = first_online_pgdat()->node_zones;
> +
> +	do {
> +		if (test_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags))
> +			page_reporting_cycle(zone, phdev);
> +
> +		/*
> +		 * Move to next zone, if at the end of the list
> +		 * test to see if we can just go into idle.
> +		 */
> +		zone = next_zone(zone);
> +		if (zone)
> +			continue;
> +		zone = first_online_pgdat()->node_zones;
> +
> +		/*
> +		 * As long as refcnt has not reached zero there are still
> +		 * zones to be processed.
> +		 */

can you please explain the reason why you are not using
for_each_populated_zone() here?


> +	} while (atomic_read(&phdev->refcnt));
> +}
> +
> +/* request page reporting on this zone */
> +void __page_reporting_request(struct zone *zone)
> +{
> +	struct page_reporting_dev_info *phdev;
> +
> +	rcu_read_lock();
> +
> +	/*
> +	 * We use RCU to protect the ph_dev_info pointer. In almost all
> +	 * cases this should be present, however in the unlikely case of
> +	 * a shutdown this will be NULL and we should exit.
> +	 */
> +	phdev = rcu_dereference(ph_dev_info);
> +	if (unlikely(!phdev))
> +		return;
> +
> +	/*
> +	 * We can use separate test and set operations here as there
> +	 * is nothing else that can set or clear this bit while we are
> +	 * holding the zone lock. The advantage to doing it this way is
> +	 * that we don't have to dirty the cacheline unless we are
> +	 * changing the value.
> +	 */
> +	__set_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags);
> +
> +	/*
> +	 * Delay the start of work to allow a sizable queue to
> +	 * build. For now we are limiting this to running no more
> +	 * than 10 times per second.
> +	 */
> +	if (!atomic_fetch_inc(&phdev->refcnt))
> +		schedule_delayed_work(&phdev->work, HZ / 10);
> +
> +	rcu_read_unlock();
> +}
> +
> +void __page_reporting_free_stats(struct zone *zone)
> +{
> +	/* free reported_page statisitics */
> +	kfree(zone->reported_pages);
> +	zone->reported_pages = NULL;
> +}
> +
> +static DEFINE_MUTEX(page_reporting_mutex);
> +
> +void page_reporting_shutdown(struct page_reporting_dev_info *phdev)
> +{
> +	mutex_lock(page_reporting_mutex);
> +
> +	if (rcu_access_pointer(ph_dev_info) == phdev) {
> +		/* Disable page reporting notification */
> +		static_key_slow_dec(&page_reporting_notify_enabled);
> +		RCU_INIT_POINTER(ph_dev_info, NULL);
> +		synchronize_rcu();
> +
> +		/* Flush any existing work, and lock it out */
> +		cancel_delayed_work_sync(&phdev->work);
> +
> +		/* Free scatterlist */
> +		kfree(phdev->sg);
> +		phdev->sg = NULL;
> +	}
> +
> +	mutex_unlock(page_reporting_mutex);
> +}
> +EXPORT_SYMBOL_GPL(page_reporting_shutdown);
> +
> +int page_reporting_startup(struct page_reporting_dev_info *phdev)
> +{
> +	struct zone *zone;
> +	int err = 0;
> +
> +	mutex_lock(page_reporting_mutex);
> +
> +	/* nothing to do if already in use */
> +	if (rcu_access_pointer(ph_dev_info)) {
> +		err = -EBUSY;
> +		goto err_out;
> +	}
> +
> +	/* allocate scatterlist to store pages being reported on */
> +	phdev->sg = kcalloc(phdev->capacity, sizeof(*phdev->sg), GFP_KERNEL);
> +	if (!phdev->sg) {
> +		err = -ENOMEM;
> +		goto err_out;
> +	}
> +
> +	/* initialize refcnt and work structures */
> +	atomic_set(&phdev->refcnt, 0);
> +	INIT_DELAYED_WORK(&phdev->work, &page_reporting_process);
> +
> +	/* assign device, and begin initial flush of populated zones */
> +	rcu_assign_pointer(ph_dev_info, phdev);
> +	for_each_populated_zone(zone) {
> +		spin_lock(&zone->lock);
> +		__page_reporting_request(zone);
> +		spin_unlock(&zone->lock);
> +	}
> +
> +	/* enable page reporting notification */
> +	static_key_slow_inc(&page_reporting_notify_enabled);
> +err_out:
> +	mutex_unlock(page_reporting_mutex);
> +
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(page_reporting_startup);
> +
>
-- 
Thanks
Nitesh

^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v4 4/6] mm: Introduce Reported pages
  2019-08-08 13:45   ` Nitesh Narayan Lal
@ 2019-08-08 15:11     ` Alexander Duyck
  0 siblings, 0 replies; 17+ messages in thread
From: Alexander Duyck @ 2019-08-08 15:11 UTC (permalink / raw)
  To: Nitesh Narayan Lal, Alexander Duyck, kvm, david, mst,
	dave.hansen, linux-kernel, linux-mm, akpm
  Cc: yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams

On Thu, 2019-08-08 at 09:45 -0400, Nitesh Narayan Lal wrote:
> On 8/7/19 6:42 PM, Alexander Duyck wrote:
> > From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> > 
> > In order to pave the way for free page reporting in virtualized
> > environments we will need a way to get pages out of the free lists and
> > identify those pages after they have been returned. To accomplish this,
> > this patch adds the concept of a Reported Buddy, which is essentially
> > meant to just be the Uptodate flag used in conjunction with the Buddy
> > page type.
> > 
> > It adds a set of pointers we shall call "boundary" which represents the
> > upper boundary between the unreported and reported pages. The general idea
> > is that in order for a page to cross from one side of the boundary to the
> > other it will need to go through the reporting process. Ultimately a
> > free_list has been fully processed when the boundary has been moved from
> > the tail all they way up to occupying the first entry in the list.
> > 
> > Doing this we should be able to make certain that we keep the reported
> > pages as one contiguous block in each free list. This will allow us to
> > efficiently manipulate the free lists whenever we need to go in and start
> > sending reports to the hypervisor that there are new pages that have been
> > freed and are no longer in use.
> > 
> > An added advantage to this approach is that we should be reducing the
> > overall memory footprint of the guest as it will be more likely to recycle
> > warm pages versus trying to allocate the reported pages that were likely
> > evicted from the guest memory.
> > 
> > Since we will only be reporting one zone at a time we keep the boundary
> > limited to being defined for just the zone we are currently reporting pages
> > from. Doing this we can keep the number of additional pointers needed quite
> > small. To flag that the boundaries are in place we use a single bit
> > in the zone to indicate that reporting and the boundaries are active.
> > 
> > The determination of when to start reporting is based on the tracking of
> > the number of free pages in a given area versus the number of reported
> > pages in that area. We keep track of the number of reported pages per
> > free_area in a separate zone specific area. We do this to avoid modifying
> > the free_area structure as this can lead to false sharing for the highest
> > order with the zone lock which leads to a noticeable performance
> > degradation.
> > 
> > Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> > ---
> >  include/linux/mmzone.h         |   40 +++++
> >  include/linux/page-flags.h     |   11 +
> >  include/linux/page_reporting.h |  138 ++++++++++++++++++
> >  mm/Kconfig                     |    5 +
> >  mm/Makefile                    |    1 
> >  mm/memory_hotplug.c            |    1 
> >  mm/page_alloc.c                |  136 +++++++++++++++++
> >  mm/page_reporting.c            |  313 ++++++++++++++++++++++++++++++++++++++++
> >  8 files changed, 637 insertions(+), 8 deletions(-)
> >  create mode 100644 include/linux/page_reporting.h
> >  create mode 100644 mm/page_reporting.c
> > 
> > 

<snip>

> > diff --git a/mm/page_reporting.c b/mm/page_reporting.c
> > new file mode 100644
> > index 000000000000..ae26dd77bce9
> > --- /dev/null
> > +++ b/mm/page_reporting.c
> > @@ -0,0 +1,313 @@

<snip>

> > +/*
> > + * The page reporting cycle consists of 4 stages, fill, report, drain, and idle.
> > + * We will cycle through the first 3 stages until we fail to obtain any
> > + * pages, in that case we will switch to idle.
> > + */
> > +static void page_reporting_cycle(struct zone *zone,
> > +				 struct page_reporting_dev_info *phdev)
> > +{
> > +	/*
> > +	 * Guarantee boundaries and stats are populated before we
> > +	 * start placing reported pages in the zone.
> > +	 */
> > +	if (page_reporting_populate_metadata(zone))
> > +		return;
> > +
> > +	spin_lock(&zone->lock);
> > +
> > +	/* set bit indicating boundaries are present */
> > +	__set_bit(ZONE_PAGE_REPORTING_ACTIVE, &zone->flags);
> > +
> > +	do {
> > +		/* Pull pages out of allocator into a scaterlist */
> > +		unsigned int nents = page_reporting_fill(zone, phdev);
> > +
> > +		/* no pages were acquired, give up */
> > +		if (!nents)
> > +			break;
> > +
> > +		spin_unlock(&zone->lock);
> > +
> > +		/* begin processing pages in local list */
> > +		phdev->report(phdev, nents);
> > +
> > +		spin_lock(&zone->lock);
> > +
> > +		/*
> > +		 * We should have a scatterlist of pages that have been
> > +		 * processed. Return them to their original free lists.
> > +		 */
> > +		page_reporting_drain(zone, phdev);
> > +
> > +		/* keep pulling pages till there are none to pull */
> > +	} while (test_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags));
> > +
> > +	/* processing of the zone is complete, we can disable boundaries */
> > +	__clear_bit(ZONE_PAGE_REPORTING_ACTIVE, &zone->flags);
> > +
> > +	spin_unlock(&zone->lock);
> > +}
> > +
> > +static void page_reporting_process(struct work_struct *work)
> > +{
> > +	struct delayed_work *d_work = to_delayed_work(work);
> > +	struct page_reporting_dev_info *phdev =
> > +		container_of(d_work, struct page_reporting_dev_info, work);
> > +	struct zone *zone = first_online_pgdat()->node_zones;
> > +
> > +	do {
> > +		if (test_bit(ZONE_PAGE_REPORTING_REQUESTED, &zone->flags))
> > +			page_reporting_cycle(zone, phdev);
> > +
> > +		/*
> > +		 * Move to next zone, if at the end of the list
> > +		 * test to see if we can just go into idle.
> > +		 */
> > +		zone = next_zone(zone);
> > +		if (zone)
> > +			continue;
> > +		zone = first_online_pgdat()->node_zones;
> > +
> > +		/*
> > +		 * As long as refcnt has not reached zero there are still
> > +		 * zones to be processed.
> > +		 */
> 
> can you please explain the reason why you are not using
> for_each_populated_zone() here?
> 
> 
> > +	} while (atomic_read(&phdev->refcnt));
> > +}
> > +

It mostly has to do with the way this code evolved. Originally I had this
starting at the last zone that was processed and resuming there with the
assumption that a noisy zone was going to trigger frequent events so why
walk the zones each time. However we aren't starting the loop that often
so I just decided to start at the beginning and walk the zones until I
found the one that had requested the reporting.

Also I probably wouldn't bother with the "populated" version of the call
since we already have a field to search for so it would just be a matter
of creating my own macro that would only give us zones that are requesting
reporting.

The last bit is that really the exit condition isn't that we hit the end
of the zone list. The exit condition for this loop is that phdev->refcnt
is zero. The problem with using for_each_zone is that you would keep
walking the zone list anyway until you hit the end of it even if we have
already processed the zones that requested reporting.


^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v4 6/6] virtio-balloon: Add support for providing unused page reports to host
  2019-08-07 22:42 ` [PATCH v4 6/6] virtio-balloon: Add support for providing unused page reports to host Alexander Duyck
@ 2019-08-12  9:53   ` Michael S. Tsirkin
  2019-08-12 15:20     ` Alexander Duyck
  0 siblings, 1 reply; 17+ messages in thread
From: Michael S. Tsirkin @ 2019-08-12  9:53 UTC (permalink / raw)
  To: Alexander Duyck
  Cc: nitesh, kvm, david, dave.hansen, linux-kernel, linux-mm, akpm,
	yang.zhang.wz, pagupta, riel, konrad.wilk, willy, lcapitulino,
	wei.w.wang, aarcange, pbonzini, dan.j.williams,
	alexander.h.duyck

On Wed, Aug 07, 2019 at 03:42:19PM -0700, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> 
> Add support for the page reporting feature provided by virtio-balloon.
> Reporting differs from the regular balloon functionality in that is is
> much less durable than a standard memory balloon. Instead of creating a
> list of pages that cannot be accessed the pages are only inaccessible
> while they are being indicated to the virtio interface. Once the
> interface has acknowledged them they are placed back into their respective
> free lists and are once again accessible by the guest system.
> 
> Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> ---
>  drivers/virtio/Kconfig              |    1 +
>  drivers/virtio/virtio_balloon.c     |   65 +++++++++++++++++++++++++++++++++++
>  include/uapi/linux/virtio_balloon.h |    1 +
>  3 files changed, 67 insertions(+)
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 078615cf2afc..4b2dd8259ff5 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -58,6 +58,7 @@ config VIRTIO_BALLOON
>  	tristate "Virtio balloon driver"
>  	depends on VIRTIO
>  	select MEMORY_BALLOON
> +	select PAGE_REPORTING
>  	---help---
>  	 This driver supports increasing and decreasing the amount
>  	 of memory within a KVM guest.
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 2c19457ab573..52f9eeda1877 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -19,6 +19,7 @@
>  #include <linux/mount.h>
>  #include <linux/magic.h>
>  #include <linux/pseudo_fs.h>
> +#include <linux/page_reporting.h>
>  
>  /*
>   * Balloon device works in 4K page units.  So each page is pointed to by
> @@ -37,6 +38,9 @@
>  #define VIRTIO_BALLOON_FREE_PAGE_SIZE \
>  	(1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT))
>  
> +/*  limit on the number of pages that can be on the reporting vq */
> +#define VIRTIO_BALLOON_VRING_HINTS_MAX	16
> +
>  #ifdef CONFIG_BALLOON_COMPACTION
>  static struct vfsmount *balloon_mnt;
>  #endif
> @@ -46,6 +50,7 @@ enum virtio_balloon_vq {
>  	VIRTIO_BALLOON_VQ_DEFLATE,
>  	VIRTIO_BALLOON_VQ_STATS,
>  	VIRTIO_BALLOON_VQ_FREE_PAGE,
> +	VIRTIO_BALLOON_VQ_REPORTING,
>  	VIRTIO_BALLOON_VQ_MAX
>  };
>  
> @@ -113,6 +118,10 @@ struct virtio_balloon {
>  
>  	/* To register a shrinker to shrink memory upon memory pressure */
>  	struct shrinker shrinker;
> +
> +	/* Unused page reporting device */
> +	struct virtqueue *reporting_vq;
> +	struct page_reporting_dev_info ph_dev_info;
>  };
>  
>  static struct virtio_device_id id_table[] = {
> @@ -152,6 +161,32 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
>  
>  }
>  
> +void virtballoon_unused_page_report(struct page_reporting_dev_info *ph_dev_info,
> +				    unsigned int nents)
> +{
> +	struct virtio_balloon *vb =
> +		container_of(ph_dev_info, struct virtio_balloon, ph_dev_info);
> +	struct virtqueue *vq = vb->reporting_vq;
> +	unsigned int unused, err;
> +
> +	/* We should always be able to add these buffers to an empty queue. */
> +	err = virtqueue_add_inbuf(vq, ph_dev_info->sg, nents, vb,
> +				  GFP_NOWAIT | __GFP_NOWARN);
> +
> +	/*
> +	 * In the extremely unlikely case that something has changed and we
> +	 * are able to trigger an error we will simply display a warning
> +	 * and exit without actually processing the pages.
> +	 */
> +	if (WARN_ON(err))
> +		return;
> +
> +	virtqueue_kick(vq);
> +
> +	/* When host has read buffer, this completes via balloon_ack */
> +	wait_event(vb->acked, virtqueue_get_buf(vq, &unused));
> +}
> +
>  static void set_page_pfns(struct virtio_balloon *vb,
>  			  __virtio32 pfns[], struct page *page)
>  {
> @@ -476,6 +511,7 @@ static int init_vqs(struct virtio_balloon *vb)
>  	names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
>  	names[VIRTIO_BALLOON_VQ_STATS] = NULL;
>  	names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
> +	names[VIRTIO_BALLOON_VQ_REPORTING] = NULL;
>  
>  	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
>  		names[VIRTIO_BALLOON_VQ_STATS] = "stats";
> @@ -487,11 +523,19 @@ static int init_vqs(struct virtio_balloon *vb)
>  		callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
>  	}
>  
> +	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
> +		names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq";
> +		callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack;
> +	}
> +
>  	err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
>  					 vqs, callbacks, names, NULL, NULL);
>  	if (err)
>  		return err;
>  
> +	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
> +		vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
> +
>  	vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
>  	vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
>  	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> @@ -931,12 +975,30 @@ static int virtballoon_probe(struct virtio_device *vdev)
>  		if (err)
>  			goto out_del_balloon_wq;
>  	}
> +
> +	vb->ph_dev_info.report = virtballoon_unused_page_report;
> +	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
> +		unsigned int capacity;
> +
> +		capacity = min_t(unsigned int,
> +				 virtqueue_get_vring_size(vb->reporting_vq) - 1,
> +				 VIRTIO_BALLOON_VRING_HINTS_MAX);
> +		vb->ph_dev_info.capacity = capacity;
> +
> +		err = page_reporting_startup(&vb->ph_dev_info);
> +		if (err)
> +			goto out_unregister_shrinker;
> +	}
> +
>  	virtio_device_ready(vdev);
>  
>  	if (towards_target(vb))
>  		virtballoon_changed(vdev);
>  	return 0;
>  
> +out_unregister_shrinker:
> +	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> +		virtio_balloon_unregister_shrinker(vb);
>  out_del_balloon_wq:
>  	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
>  		destroy_workqueue(vb->balloon_wq);
> @@ -965,6 +1027,8 @@ static void virtballoon_remove(struct virtio_device *vdev)
>  {
>  	struct virtio_balloon *vb = vdev->priv;
>  
> +	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
> +		page_reporting_shutdown(&vb->ph_dev_info);
>  	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
>  		virtio_balloon_unregister_shrinker(vb);
>  	spin_lock_irq(&vb->stop_update_lock);
> @@ -1034,6 +1098,7 @@ static int virtballoon_validate(struct virtio_device *vdev)
>  	VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
>  	VIRTIO_BALLOON_F_FREE_PAGE_HINT,
>  	VIRTIO_BALLOON_F_PAGE_POISON,
> +	VIRTIO_BALLOON_F_REPORTING,
>  };
>  
>  static struct virtio_driver virtio_balloon_driver = {
> diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
> index a1966cd7b677..19974392d324 100644
> --- a/include/uapi/linux/virtio_balloon.h
> +++ b/include/uapi/linux/virtio_balloon.h
> @@ -36,6 +36,7 @@
>  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */
>  #define VIRTIO_BALLOON_F_FREE_PAGE_HINT	3 /* VQ to report free pages */
>  #define VIRTIO_BALLOON_F_PAGE_POISON	4 /* Guest is using page poisoning */
> +#define VIRTIO_BALLOON_F_REPORTING	5 /* Page reporting virtqueue */
>  
>  /* Size of a PFN in the balloon interface. */
>  #define VIRTIO_BALLOON_PFN_SHIFT 12

Just a small comment: same as any feature bit,
or indeed any host/guest interface changes, please
CC virtio-dev on any changes to this UAPI file.
We must maintain these in the central place in the spec,
otherwise we run a risk of conflicts.

-- 
MST

^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v4 6/6] virtio-balloon: Add support for providing unused page reports to host
  2019-08-12  9:53   ` Michael S. Tsirkin
@ 2019-08-12 15:20     ` Alexander Duyck
  2019-08-12 15:43       ` Michael S. Tsirkin
  2019-08-12 15:49       ` David Hildenbrand
  0 siblings, 2 replies; 17+ messages in thread
From: Alexander Duyck @ 2019-08-12 15:20 UTC (permalink / raw)
  To: Michael S. Tsirkin
  Cc: Nitesh Narayan Lal, kvm list, David Hildenbrand, Dave Hansen,
	LKML, linux-mm, Andrew Morton, Yang Zhang, pagupta, Rik van Riel,
	Konrad Rzeszutek Wilk, Matthew Wilcox, lcapitulino, wei.w.wang,
	Andrea Arcangeli, Paolo Bonzini, dan.j.williams, Alexander Duyck

On Mon, Aug 12, 2019 at 2:53 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Wed, Aug 07, 2019 at 03:42:19PM -0700, Alexander Duyck wrote:
> > From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

<snip>

> > --- a/include/uapi/linux/virtio_balloon.h
> > +++ b/include/uapi/linux/virtio_balloon.h
> > @@ -36,6 +36,7 @@
> >  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM      2 /* Deflate balloon on OOM */
> >  #define VIRTIO_BALLOON_F_FREE_PAGE_HINT      3 /* VQ to report free pages */
> >  #define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */
> > +#define VIRTIO_BALLOON_F_REPORTING   5 /* Page reporting virtqueue */
> >
> >  /* Size of a PFN in the balloon interface. */
> >  #define VIRTIO_BALLOON_PFN_SHIFT 12
>
> Just a small comment: same as any feature bit,
> or indeed any host/guest interface changes, please
> CC virtio-dev on any changes to this UAPI file.
> We must maintain these in the central place in the spec,
> otherwise we run a risk of conflicts.
>

Okay, other than that if I resubmit with the virtio-dev list added to
you thing this patch set is ready to be acked and pulled into either
the virtio or mm tree assuming there is no other significant feedback
that comes in?

Thanks.

- Alex

^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v4 6/6] virtio-balloon: Add support for providing unused page reports to host
  2019-08-12 15:20     ` Alexander Duyck
@ 2019-08-12 15:43       ` Michael S. Tsirkin
  2019-08-12 15:49       ` David Hildenbrand
  1 sibling, 0 replies; 17+ messages in thread
From: Michael S. Tsirkin @ 2019-08-12 15:43 UTC (permalink / raw)
  To: Alexander Duyck
  Cc: Nitesh Narayan Lal, kvm list, David Hildenbrand, Dave Hansen,
	LKML, linux-mm, Andrew Morton, Yang Zhang, pagupta, Rik van Riel,
	Konrad Rzeszutek Wilk, Matthew Wilcox, lcapitulino, wei.w.wang,
	Andrea Arcangeli, Paolo Bonzini, dan.j.williams, Alexander Duyck

On Mon, Aug 12, 2019 at 08:20:43AM -0700, Alexander Duyck wrote:
> On Mon, Aug 12, 2019 at 2:53 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Wed, Aug 07, 2019 at 03:42:19PM -0700, Alexander Duyck wrote:
> > > From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> 
> <snip>
> 
> > > --- a/include/uapi/linux/virtio_balloon.h
> > > +++ b/include/uapi/linux/virtio_balloon.h
> > > @@ -36,6 +36,7 @@
> > >  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM      2 /* Deflate balloon on OOM */
> > >  #define VIRTIO_BALLOON_F_FREE_PAGE_HINT      3 /* VQ to report free pages */
> > >  #define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */
> > > +#define VIRTIO_BALLOON_F_REPORTING   5 /* Page reporting virtqueue */
> > >
> > >  /* Size of a PFN in the balloon interface. */
> > >  #define VIRTIO_BALLOON_PFN_SHIFT 12
> >
> > Just a small comment: same as any feature bit,
> > or indeed any host/guest interface changes, please
> > CC virtio-dev on any changes to this UAPI file.
> > We must maintain these in the central place in the spec,
> > otherwise we run a risk of conflicts.
> >
> 
> Okay, other than that if I resubmit with the virtio-dev list added to
> you thing this patch set is ready to be acked and pulled into either
> the virtio or mm tree assuming there is no other significant feedback
> that comes in?
> 
> Thanks.
> 
> - Alex


From my POV yes. If it's my tree acks by mm folks will be necessary.

-- 
MST

^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v4 6/6] virtio-balloon: Add support for providing unused page reports to host
  2019-08-12 15:20     ` Alexander Duyck
  2019-08-12 15:43       ` Michael S. Tsirkin
@ 2019-08-12 15:49       ` David Hildenbrand
  2019-08-12 16:09         ` Alexander Duyck
  1 sibling, 1 reply; 17+ messages in thread
From: David Hildenbrand @ 2019-08-12 15:49 UTC (permalink / raw)
  To: Alexander Duyck, Michael S. Tsirkin
  Cc: Nitesh Narayan Lal, kvm list, Dave Hansen, LKML, linux-mm,
	Andrew Morton, Yang Zhang, pagupta, Rik van Riel,
	Konrad Rzeszutek Wilk, Matthew Wilcox, lcapitulino, wei.w.wang,
	Andrea Arcangeli, Paolo Bonzini, dan.j.williams, Alexander Duyck,
	Michal Hocko, Oscar Salvador

On 12.08.19 17:20, Alexander Duyck wrote:
> On Mon, Aug 12, 2019 at 2:53 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>>
>> On Wed, Aug 07, 2019 at 03:42:19PM -0700, Alexander Duyck wrote:
>>> From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> 
> <snip>
> 
>>> --- a/include/uapi/linux/virtio_balloon.h
>>> +++ b/include/uapi/linux/virtio_balloon.h
>>> @@ -36,6 +36,7 @@
>>>  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM      2 /* Deflate balloon on OOM */
>>>  #define VIRTIO_BALLOON_F_FREE_PAGE_HINT      3 /* VQ to report free pages */
>>>  #define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */
>>> +#define VIRTIO_BALLOON_F_REPORTING   5 /* Page reporting virtqueue */
>>>
>>>  /* Size of a PFN in the balloon interface. */
>>>  #define VIRTIO_BALLOON_PFN_SHIFT 12
>>
>> Just a small comment: same as any feature bit,
>> or indeed any host/guest interface changes, please
>> CC virtio-dev on any changes to this UAPI file.
>> We must maintain these in the central place in the spec,
>> otherwise we run a risk of conflicts.
>>
> 
> Okay, other than that if I resubmit with the virtio-dev list added to
> you thing this patch set is ready to be acked and pulled into either
> the virtio or mm tree assuming there is no other significant feedback
> that comes in?
> 

I want to take a detailed look at the mm bits (might take a bit but I
don't see a need to rush). I am fine with the page flag we are using.
Hope some other mm people (cc'ing Michal and Oscar) can have a look.

-- 

Thanks,

David / dhildenb

^ permalink raw reply	[flat|nested] 17+ messages in thread

* Re: [PATCH v4 6/6] virtio-balloon: Add support for providing unused page reports to host
  2019-08-12 15:49       ` David Hildenbrand
@ 2019-08-12 16:09         ` Alexander Duyck
  0 siblings, 0 replies; 17+ messages in thread
From: Alexander Duyck @ 2019-08-12 16:09 UTC (permalink / raw)
  To: David Hildenbrand
  Cc: Michael S. Tsirkin, Nitesh Narayan Lal, kvm list, Dave Hansen,
	LKML, linux-mm, Andrew Morton, Yang Zhang, pagupta, Rik van Riel,
	Konrad Rzeszutek Wilk, Matthew Wilcox, lcapitulino, wei.w.wang,
	Andrea Arcangeli, Paolo Bonzini, dan.j.williams, Alexander Duyck,
	Michal Hocko, Oscar Salvador

On Mon, Aug 12, 2019 at 8:50 AM David Hildenbrand <david@redhat.com> wrote:
>
> On 12.08.19 17:20, Alexander Duyck wrote:
> > On Mon, Aug 12, 2019 at 2:53 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >>
> >> On Wed, Aug 07, 2019 at 03:42:19PM -0700, Alexander Duyck wrote:
> >>> From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> >
> > <snip>
> >
> >>> --- a/include/uapi/linux/virtio_balloon.h
> >>> +++ b/include/uapi/linux/virtio_balloon.h
> >>> @@ -36,6 +36,7 @@
> >>>  #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM      2 /* Deflate balloon on OOM */
> >>>  #define VIRTIO_BALLOON_F_FREE_PAGE_HINT      3 /* VQ to report free pages */
> >>>  #define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */
> >>> +#define VIRTIO_BALLOON_F_REPORTING   5 /* Page reporting virtqueue */
> >>>
> >>>  /* Size of a PFN in the balloon interface. */
> >>>  #define VIRTIO_BALLOON_PFN_SHIFT 12
> >>
> >> Just a small comment: same as any feature bit,
> >> or indeed any host/guest interface changes, please
> >> CC virtio-dev on any changes to this UAPI file.
> >> We must maintain these in the central place in the spec,
> >> otherwise we run a risk of conflicts.
> >>
> >
> > Okay, other than that if I resubmit with the virtio-dev list added to
> > you thing this patch set is ready to be acked and pulled into either
> > the virtio or mm tree assuming there is no other significant feedback
> > that comes in?
> >
>
> I want to take a detailed look at the mm bits (might take a bit but I
> don't see a need to rush). I am fine with the page flag we are using.
> Hope some other mm people (cc'ing Michal and Oscar) can have a look.

Agreed. I just wanted to make sure we had the virtio bits locked in as
my concern was that some of the other MM maintainers might be waiting
on that.

I'll see about submitting a v5, hopefully before the end of today with
Michal, Oscar, and the virtio-dev mailing list also included.

Thanks.

- Alex

^ permalink raw reply	[flat|nested] 17+ messages in thread

end of thread, back to index

Thread overview: 17+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-07 22:41 [PATCH v4 0/6] mm / virtio: Provide support for unused page reporting Alexander Duyck
2019-08-07 22:41 ` [PATCH v4 1/6] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
2019-08-07 22:41 ` [PATCH v4 2/6] mm: Move set/get_pcppage_migratetype to mmzone.h Alexander Duyck
2019-08-07 22:42 ` [PATCH v4 3/6] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck
2019-08-07 22:42 ` [PATCH v4 4/6] mm: Introduce Reported pages Alexander Duyck
2019-08-08 13:45   ` Nitesh Narayan Lal
2019-08-08 15:11     ` Alexander Duyck
2019-08-07 22:42 ` [PATCH v4 5/6] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck
2019-08-07 22:42 ` [PATCH v4 6/6] virtio-balloon: Add support for providing unused page reports to host Alexander Duyck
2019-08-12  9:53   ` Michael S. Tsirkin
2019-08-12 15:20     ` Alexander Duyck
2019-08-12 15:43       ` Michael S. Tsirkin
2019-08-12 15:49       ` David Hildenbrand
2019-08-12 16:09         ` Alexander Duyck
2019-08-07 22:43 ` [PATCH v4 QEMU 1/3] virtio-ballon: Implement support for page poison tracking feature Alexander Duyck
2019-08-07 22:43 ` [PATCH v4 QEMU 2/3] virtio-balloon: Add bit to notify guest of unused page reporting Alexander Duyck
2019-08-07 22:43 ` [PATCH v4 QEMU 3/3] virtio-balloon: Provide a interface for " Alexander Duyck

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