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[PATCH -v3 00/10] THP swap: Delay splitting THP during swapping out

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  [PATCH -v3 00/10] THP swap: Delay splitting THP during swapping out "Huang, Ying" <ying.huang@intel.com> - 2016-09-07 18:50 +0200
    [PATCH -v3 02/10] mm, memcg: Add swap_cgroup_iter iterator "Huang, Ying" <ying.huang@intel.com> - 2016-09-07 18:50 +0200
    [PATCH -v3 08/10] mm, THP: Add can_split_huge_page() "Huang, Ying" <ying.huang@intel.com> - 2016-09-07 18:50 +0200
      Re: [PATCH -v3 08/10] mm, THP: Add can_split_huge_page() "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-09-08 13:20 +0200
        Re: [PATCH -v3 08/10] mm, THP: Add can_split_huge_page() "Huang\, Ying" <ying.huang@intel.com> - 2016-09-08 19:10 +0200
    [PATCH -v3 01/10] mm, swap: Make swap cluster size same of THP size on x86_64 "Huang, Ying" <ying.huang@intel.com> - 2016-09-07 18:50 +0200
      Re: [PATCH -v3 01/10] mm, swap: Make swap cluster size same of THP  size on x86_64 Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2016-09-08 10:30 +0200
      Re: [PATCH -v3 01/10] mm, swap: Make swap cluster size same of THP  size on x86_64 Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2016-09-08 11:20 +0200
        Re: [PATCH -v3 01/10] mm, swap: Make swap cluster size same of THP size on x86_64 "Huang\, Ying" <ying.huang@intel.com> - 2016-09-08 20:10 +0200
      Re: [PATCH -v3 01/10] mm, swap: Make swap cluster size same of THP  size on x86_64 "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-09-08 13:10 +0200
        Re: [PATCH -v3 01/10] mm, swap: Make swap cluster size same of THP size on x86_64 "Huang\, Ying" <ying.huang@intel.com> - 2016-09-08 19:40 +0200
      Re: [PATCH -v3 01/10] mm, swap: Make swap cluster size same of THP  size on x86_64 "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-09-08 13:10 +0200
        Re: [PATCH -v3 01/10] mm, swap: Make swap cluster size same of THP size on x86_64 "Huang\, Ying" <ying.huang@intel.com> - 2016-09-08 19:30 +0200
    [PATCH -v3 05/10] mm, THP, swap: Add get_huge_swap_page() "Huang, Ying" <ying.huang@intel.com> - 2016-09-07 18:50 +0200
      Re: [PATCH -v3 05/10] mm, THP, swap: Add get_huge_swap_page() "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-09-08 13:20 +0200
        Re: [PATCH -v3 05/10] mm, THP, swap: Add get_huge_swap_page() "Huang\, Ying" <ying.huang@intel.com> - 2016-09-08 19:30 +0200
    [PATCH -v3 09/10] mm, THP, swap: Support to split THP in swap cache "Huang, Ying" <ying.huang@intel.com> - 2016-09-07 18:50 +0200
    [PATCH -v3 06/10] mm, THP, swap: Support to clear SWAP_HAS_CACHE for huge page "Huang, Ying" <ying.huang@intel.com> - 2016-09-07 18:50 +0200
    [PATCH -v3 03/10] mm, memcg: Support to charge/uncharge multiple swap entries "Huang, Ying" <ying.huang@intel.com> - 2016-09-07 18:50 +0200
      Re: [PATCH -v3 03/10] mm, memcg: Support to charge/uncharge multiple  swap entries Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2016-09-08 10:30 +0200
        Re: [PATCH -v3 03/10] mm, memcg: Support to charge/uncharge multiple swap entries "Huang\, Ying" <ying.huang@intel.com> - 2016-09-08 20:20 +0200
      Re: [PATCH -v3 03/10] mm, memcg: Support to charge/uncharge multiple  swap entries Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2016-09-08 10:40 +0200
    [PATCH -v3 04/10] mm, THP, swap: Add swap cluster allocate/free functions "Huang, Ying" <ying.huang@intel.com> - 2016-09-07 18:50 +0200
      Re: [PATCH -v3 04/10] mm, THP, swap: Add swap cluster allocate/free  functions Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2016-09-08 10:40 +0200
        Re: [PATCH -v3 04/10] mm, THP, swap: Add swap cluster allocate/free functions "Huang\, Ying" <ying.huang@intel.com> - 2016-09-08 20:20 +0200
      Re: [PATCH -v3 04/10] mm, THP, swap: Add swap cluster allocate/free  functions Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2016-09-08 11:00 +0200
    [PATCH -v3 07/10] mm, THP, swap: Support to add/delete THP to/from swap cache "Huang, Ying" <ying.huang@intel.com> - 2016-09-07 18:50 +0200
      Re: [PATCH -v3 07/10] mm, THP, swap: Support to add/delete THP to/from  swap cache Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2016-09-08 11:10 +0200
        Re: [PATCH -v3 07/10] mm, THP, swap: Support to add/delete THP to/from swap cache "Huang\, Ying" <ying.huang@intel.com> - 2016-09-08 20:20 +0200
    Re: [PATCH -v3 00/10] THP swap: Delay splitting THP during swapping  out Minchan Kim <minchan@kernel.org> - 2016-09-09 07:50 +0200

Page 2 of 2 — ← Prev page 1 [2]

#1479420 — Re: [PATCH -v3 03/10] mm, memcg: Support to charge/uncharge multiple swap entries

Anshuman Khandual <khandual@linux.vnet.ibm.com> writes:

> On 09/07/2016 10:16 PM, Huang, Ying wrote:
>> From: Huang Ying <ying.huang@intel.com>
>> 
>> This patch make it possible to charge or uncharge a set of continuous
>> swap entries in the swap cgroup.  The number of swap entries is
>> specified via an added parameter.
>> 
>> This will be used for the THP (Transparent Huge Page) swap support.
>> Where a swap cluster backing a THP may be allocated and freed as a
>> whole.  So a set of continuous swap entries (512 on x86_64) backing one
>
> Please use HPAGE_SIZE / PAGE_SIZE instead of hard coded number like 512.

Sure.  Will change it.

Best Regards,
Huang, Ying

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#1478925 — Re: [PATCH -v3 03/10] mm, memcg: Support to charge/uncharge multiple swap entries

On 09/07/2016 10:16 PM, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
> 
> This patch make it possible to charge or uncharge a set of continuous
> swap entries in the swap cgroup.  The number of swap entries is
> specified via an added parameter.
> 
> This will be used for the THP (Transparent Huge Page) swap support.
> Where a swap cluster backing a THP may be allocated and freed as a
> whole.  So a set of continuous swap entries (512 on x86_64) backing one

Please use HPAGE_SIZE / PAGE_SIZE instead of hard coded number like 512.

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#1478501 — [PATCH -v3 04/10] mm, THP, swap: Add swap cluster allocate/free functions

From: Huang Ying <ying.huang@intel.com>

The swap cluster allocation/free functions are added based on the
existing swap cluster management mechanism for SSD.  These functions
don't work for the rotating hard disks because the existing swap cluster
management mechanism doesn't work for them.  The hard disks support may
be added if someone really need it.  But that needn't be included in
this patchset.

This will be used for the THP (Transparent Huge Page) swap support.
Where one swap cluster will hold the contents of each THP swapped out.

Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
---
 mm/swapfile.c | 203 +++++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 146 insertions(+), 57 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 17f25e2..0132e8c 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -326,6 +326,14 @@ static void swap_cluster_schedule_discard(struct swap_info_struct *si,
 	schedule_work(&si->discard_work);
 }
 
+static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
+{
+	struct swap_cluster_info *ci = si->cluster_info;
+
+	cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
+	cluster_list_add_tail(&si->free_clusters, ci, idx);
+}
+
 /*
  * Doing discard actually. After a cluster discard is finished, the cluster
  * will be added to free cluster list. caller should hold si->lock.
@@ -345,8 +353,7 @@ static void swap_do_scheduled_discard(struct swap_info_struct *si)
 				SWAPFILE_CLUSTER);
 
 		spin_lock(&si->lock);
-		cluster_set_flag(&info[idx], CLUSTER_FLAG_FREE);
-		cluster_list_add_tail(&si->free_clusters, info, idx);
+		__free_cluster(si, idx);
 		memset(si->swap_map + idx * SWAPFILE_CLUSTER,
 				0, SWAPFILE_CLUSTER);
 	}
@@ -363,6 +370,34 @@ static void swap_discard_work(struct work_struct *work)
 	spin_unlock(&si->lock);
 }
 
+static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
+{
+	struct swap_cluster_info *ci = si->cluster_info;
+
+	VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
+	cluster_list_del_first(&si->free_clusters, ci);
+	cluster_set_count_flag(ci + idx, 0, 0);
+}
+
+static void free_cluster(struct swap_info_struct *si, unsigned long idx)
+{
+	struct swap_cluster_info *ci = si->cluster_info + idx;
+
+	VM_BUG_ON(cluster_count(ci) != 0);
+	/*
+	 * If the swap is discardable, prepare discard the cluster
+	 * instead of free it immediately. The cluster will be freed
+	 * after discard.
+	 */
+	if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
+	    (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
+		swap_cluster_schedule_discard(si, idx);
+		return;
+	}
+
+	__free_cluster(si, idx);
+}
+
 /*
  * The cluster corresponding to page_nr will be used. The cluster will be
  * removed from free cluster list and its usage counter will be increased.
@@ -374,11 +409,8 @@ static void inc_cluster_info_page(struct swap_info_struct *p,
 
 	if (!cluster_info)
 		return;
-	if (cluster_is_free(&cluster_info[idx])) {
-		VM_BUG_ON(cluster_list_first(&p->free_clusters) != idx);
-		cluster_list_del_first(&p->free_clusters, cluster_info);
-		cluster_set_count_flag(&cluster_info[idx], 0, 0);
-	}
+	if (cluster_is_free(&cluster_info[idx]))
+		alloc_cluster(p, idx);
 
 	VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER);
 	cluster_set_count(&cluster_info[idx],
@@ -402,21 +434,8 @@ static void dec_cluster_info_page(struct swap_info_struct *p,
 	cluster_set_count(&cluster_info[idx],
 		cluster_count(&cluster_info[idx]) - 1);
 
-	if (cluster_count(&cluster_info[idx]) == 0) {
-		/*
-		 * If the swap is discardable, prepare discard the cluster
-		 * instead of free it immediately. The cluster will be freed
-		 * after discard.
-		 */
-		if ((p->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
-				 (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
-			swap_cluster_schedule_discard(p, idx);
-			return;
-		}
-
-		cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
-		cluster_list_add_tail(&p->free_clusters, cluster_info, idx);
-	}
+	if (cluster_count(&cluster_info[idx]) == 0)
+		free_cluster(p, idx);
 }
 
 /*
@@ -497,6 +516,69 @@ new_cluster:
 	*scan_base = tmp;
 }
 
+#ifdef CONFIG_THP_SWAP_CLUSTER
+static inline unsigned int huge_cluster_nr_entries(bool huge)
+{
+	return huge ? SWAPFILE_CLUSTER : 1;
+}
+#else
+#define huge_cluster_nr_entries(huge)	1
+#endif
+
+static void __swap_entry_alloc(struct swap_info_struct *si,
+			       unsigned long offset, bool huge)
+{
+	unsigned int nr_entries = huge_cluster_nr_entries(huge);
+	unsigned int end = offset + nr_entries - 1;
+
+	if (offset == si->lowest_bit)
+		si->lowest_bit += nr_entries;
+	if (end == si->highest_bit)
+		si->highest_bit -= nr_entries;
+	si->inuse_pages += nr_entries;
+	if (si->inuse_pages == si->pages) {
+		si->lowest_bit = si->max;
+		si->highest_bit = 0;
+		spin_lock(&swap_avail_lock);
+		plist_del(&si->avail_list, &swap_avail_head);
+		spin_unlock(&swap_avail_lock);
+	}
+}
+
+static void __swap_entry_free(struct swap_info_struct *si, unsigned long offset,
+			      bool huge)
+{
+	unsigned int nr_entries = huge_cluster_nr_entries(huge);
+	unsigned long end = offset + nr_entries - 1;
+	void (*swap_slot_free_notify)(struct block_device *, unsigned long);
+
+	if (offset < si->lowest_bit)
+		si->lowest_bit = offset;
+	if (end > si->highest_bit) {
+		bool was_full = !si->highest_bit;
+
+		si->highest_bit = end;
+		if (was_full && (si->flags & SWP_WRITEOK)) {
+			spin_lock(&swap_avail_lock);
+			WARN_ON(!plist_node_empty(&si->avail_list));
+			if (plist_node_empty(&si->avail_list))
+				plist_add(&si->avail_list, &swap_avail_head);
+			spin_unlock(&swap_avail_lock);
+		}
+	}
+	atomic_long_add(nr_entries, &nr_swap_pages);
+	si->inuse_pages -= nr_entries;
+	if (si->flags & SWP_BLKDEV)
+		swap_slot_free_notify =
+			si->bdev->bd_disk->fops->swap_slot_free_notify;
+	while (offset <= end) {
+		frontswap_invalidate_page(si->type, offset);
+		if (swap_slot_free_notify)
+			swap_slot_free_notify(si->bdev, offset);
+		offset++;
+	}
+}
+
 static unsigned long scan_swap_map(struct swap_info_struct *si,
 				   unsigned char usage)
 {
@@ -591,18 +673,7 @@ checks:
 	if (si->swap_map[offset])
 		goto scan;
 
-	if (offset == si->lowest_bit)
-		si->lowest_bit++;
-	if (offset == si->highest_bit)
-		si->highest_bit--;
-	si->inuse_pages++;
-	if (si->inuse_pages == si->pages) {
-		si->lowest_bit = si->max;
-		si->highest_bit = 0;
-		spin_lock(&swap_avail_lock);
-		plist_del(&si->avail_list, &swap_avail_head);
-		spin_unlock(&swap_avail_lock);
-	}
+	__swap_entry_alloc(si, offset, false);
 	si->swap_map[offset] = usage;
 	inc_cluster_info_page(si, si->cluster_info, offset);
 	si->cluster_next = offset + 1;
@@ -649,6 +720,46 @@ no_page:
 	return 0;
 }
 
+#ifdef CONFIG_THP_SWAP_CLUSTER
+static void swap_free_huge_cluster(struct swap_info_struct *si,
+				   unsigned long idx)
+{
+	struct swap_cluster_info *ci = si->cluster_info + idx;
+	unsigned long offset = idx * SWAPFILE_CLUSTER;
+
+	cluster_set_count_flag(ci, 0, 0);
+	free_cluster(si, idx);
+	__swap_entry_free(si, offset, true);
+}
+
+static unsigned long swap_alloc_huge_cluster(struct swap_info_struct *si)
+{
+	unsigned long idx;
+	struct swap_cluster_info *ci;
+	unsigned long offset, i;
+	unsigned char *map;
+
+	if (cluster_list_empty(&si->free_clusters))
+		return 0;
+	idx = cluster_list_first(&si->free_clusters);
+	alloc_cluster(si, idx);
+	ci = si->cluster_info + idx;
+	cluster_set_count_flag(ci, SWAPFILE_CLUSTER, 0);
+
+	offset = idx * SWAPFILE_CLUSTER;
+	__swap_entry_alloc(si, offset, true);
+	map = si->swap_map + offset;
+	for (i = 0; i < SWAPFILE_CLUSTER; i++)
+		map[i] = SWAP_HAS_CACHE;
+	return offset;
+}
+#else
+static inline unsigned long swap_alloc_huge_cluster(struct swap_info_struct *si)
+{
+	return 0;
+}
+#endif
+
 swp_entry_t get_swap_page(void)
 {
 	struct swap_info_struct *si, *next;
@@ -808,29 +919,7 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
 	if (!usage) {
 		mem_cgroup_uncharge_swap(entry, 1);
 		dec_cluster_info_page(p, p->cluster_info, offset);
-		if (offset < p->lowest_bit)
-			p->lowest_bit = offset;
-		if (offset > p->highest_bit) {
-			bool was_full = !p->highest_bit;
-			p->highest_bit = offset;
-			if (was_full && (p->flags & SWP_WRITEOK)) {
-				spin_lock(&swap_avail_lock);
-				WARN_ON(!plist_node_empty(&p->avail_list));
-				if (plist_node_empty(&p->avail_list))
-					plist_add(&p->avail_list,
-						  &swap_avail_head);
-				spin_unlock(&swap_avail_lock);
-			}
-		}
-		atomic_long_inc(&nr_swap_pages);
-		p->inuse_pages--;
-		frontswap_invalidate_page(p->type, offset);
-		if (p->flags & SWP_BLKDEV) {
-			struct gendisk *disk = p->bdev->bd_disk;
-			if (disk->fops->swap_slot_free_notify)
-				disk->fops->swap_slot_free_notify(p->bdev,
-								  offset);
-		}
+		__swap_entry_free(p, offset, false);
 	}
 
 	return usage;
-- 
2.8.1

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#1478917 — Re: [PATCH -v3 04/10] mm, THP, swap: Add swap cluster allocate/free functions

On 09/07/2016 10:16 PM, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
> 
> The swap cluster allocation/free functions are added based on the
> existing swap cluster management mechanism for SSD.  These functions
> don't work for the rotating hard disks because the existing swap cluster
> management mechanism doesn't work for them.  The hard disks support may
> be added if someone really need it.  But that needn't be included in
> this patchset.
> 
> This will be used for the THP (Transparent Huge Page) swap support.
> Where one swap cluster will hold the contents of each THP swapped out.

Which tree this series is based against ? This patch does not apply
on the mainline kernel.

[toc] | [prev] | [next] | [standalone]

#1479429 — Re: [PATCH -v3 04/10] mm, THP, swap: Add swap cluster allocate/free functions

Anshuman Khandual <khandual@linux.vnet.ibm.com> writes:

> On 09/07/2016 10:16 PM, Huang, Ying wrote:
>> From: Huang Ying <ying.huang@intel.com>
>> 
>> The swap cluster allocation/free functions are added based on the
>> existing swap cluster management mechanism for SSD.  These functions
>> don't work for the rotating hard disks because the existing swap cluster
>> management mechanism doesn't work for them.  The hard disks support may
>> be added if someone really need it.  But that needn't be included in
>> this patchset.
>> 
>> This will be used for the THP (Transparent Huge Page) swap support.
>> Where one swap cluster will hold the contents of each THP swapped out.
>
> Which tree this series is based against ? This patch does not apply
> on the mainline kernel.

This series is based on 8/31 head of mmotm/master.  I stated it in
00/10, but I know it is hided inside other text and not obvious at all.
Is there some way to make it obvious?

Best Regards,
Huang, Ying

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#1478938 — Re: [PATCH -v3 04/10] mm, THP, swap: Add swap cluster allocate/free functions

On 09/07/2016 10:16 PM, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
> 
> The swap cluster allocation/free functions are added based on the
> existing swap cluster management mechanism for SSD.  These functions
> don't work for the rotating hard disks because the existing swap cluster
> management mechanism doesn't work for them.  The hard disks support may
> be added if someone really need it.  But that needn't be included in
> this patchset.
> 
> This will be used for the THP (Transparent Huge Page) swap support.
> Where one swap cluster will hold the contents of each THP swapped out.

Which tree this series is based against ? This patch does not apply
on the mainline kernel today.

[toc] | [prev] | [next] | [standalone]

#1478502 — [PATCH -v3 07/10] mm, THP, swap: Support to add/delete THP to/from swap cache

From: Huang Ying <ying.huang@intel.com>

With this patch, a THP (Transparent Huge Page) can be added/deleted
to/from the swap cache as a set of sub-pages (512 on x86_64).

This will be used for the THP (Transparent Huge Page) swap support.
Where one THP may be added/delted to/from the swap cache.  This will
batch the swap cache operations to reduce the lock acquire/release times
for the THP swap too.

Cc: Hugh Dickins <hughd@google.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
---
 include/linux/page-flags.h |  2 +-
 mm/swap_state.c            | 57 +++++++++++++++++++++++++++++++---------------
 2 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 74e4dda..f5bcbea 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -314,7 +314,7 @@ PAGEFLAG_FALSE(HighMem)
 #endif
 
 #ifdef CONFIG_SWAP
-PAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
+PAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
 #else
 PAGEFLAG_FALSE(SwapCache)
 #endif
diff --git a/mm/swap_state.c b/mm/swap_state.c
index c335251..db2299f 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -43,6 +43,7 @@ struct address_space swapper_spaces[MAX_SWAPFILES] = {
 };
 
 #define INC_CACHE_INFO(x)	do { swap_cache_info.x++; } while (0)
+#define ADD_CACHE_INFO(x, nr)	do { swap_cache_info.x += (nr); } while (0)
 
 static struct {
 	unsigned long add_total;
@@ -80,25 +81,32 @@ void show_swap_cache_info(void)
  */
 int __add_to_swap_cache(struct page *page, swp_entry_t entry)
 {
-	int error;
+	int error, i, nr = hpage_nr_pages(page);
 	struct address_space *address_space;
 
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
 	VM_BUG_ON_PAGE(PageSwapCache(page), page);
 	VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
 
-	get_page(page);
+	page_ref_add(page, nr);
 	SetPageSwapCache(page);
-	set_page_private(page, entry.val);
 
 	address_space = swap_address_space(entry);
 	spin_lock_irq(&address_space->tree_lock);
-	error = radix_tree_insert(&address_space->page_tree,
-					entry.val, page);
+	for (i = 0; i < nr; i++) {
+		struct page *cur_page = page + i;
+		unsigned long index = entry.val + i;
+
+		set_page_private(cur_page, index);
+		error = radix_tree_insert(&address_space->page_tree,
+					  index, cur_page);
+		if (unlikely(error))
+			break;
+	}
 	if (likely(!error)) {
-		address_space->nrpages++;
-		__inc_node_page_state(page, NR_FILE_PAGES);
-		INC_CACHE_INFO(add_total);
+		address_space->nrpages += nr;
+		__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
+		ADD_CACHE_INFO(add_total, nr);
 	}
 	spin_unlock_irq(&address_space->tree_lock);
 
@@ -109,9 +117,16 @@ int __add_to_swap_cache(struct page *page, swp_entry_t entry)
 		 * So add_to_swap_cache() doesn't returns -EEXIST.
 		 */
 		VM_BUG_ON(error == -EEXIST);
-		set_page_private(page, 0UL);
 		ClearPageSwapCache(page);
-		put_page(page);
+		set_page_private(page + i, 0UL);
+		while (i--) {
+			struct page *cur_page = page + i;
+			unsigned long index = entry.val + i;
+
+			set_page_private(cur_page, 0UL);
+			radix_tree_delete(&address_space->page_tree, index);
+		}
+		page_ref_sub(page, nr);
 	}
 
 	return error;
@@ -122,7 +137,7 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
 {
 	int error;
 
-	error = radix_tree_maybe_preload(gfp_mask);
+	error = radix_tree_maybe_preload_order(gfp_mask, compound_order(page));
 	if (!error) {
 		error = __add_to_swap_cache(page, entry);
 		radix_tree_preload_end();
@@ -138,6 +153,7 @@ void __delete_from_swap_cache(struct page *page)
 {
 	swp_entry_t entry;
 	struct address_space *address_space;
+	int i, nr = hpage_nr_pages(page);
 
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
 	VM_BUG_ON_PAGE(!PageSwapCache(page), page);
@@ -145,12 +161,17 @@ void __delete_from_swap_cache(struct page *page)
 
 	entry.val = page_private(page);
 	address_space = swap_address_space(entry);
-	radix_tree_delete(&address_space->page_tree, page_private(page));
-	set_page_private(page, 0);
 	ClearPageSwapCache(page);
-	address_space->nrpages--;
-	__dec_node_page_state(page, NR_FILE_PAGES);
-	INC_CACHE_INFO(del_total);
+	for (i = 0; i < nr; i++) {
+		struct page *cur_page = page + i;
+
+		radix_tree_delete(&address_space->page_tree,
+				  page_private(cur_page));
+		set_page_private(cur_page, 0);
+	}
+	address_space->nrpages -= nr;
+	__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
+	ADD_CACHE_INFO(del_total, nr);
 }
 
 /**
@@ -227,8 +248,8 @@ void delete_from_swap_cache(struct page *page)
 	__delete_from_swap_cache(page);
 	spin_unlock_irq(&address_space->tree_lock);
 
-	swapcache_free(entry);
-	put_page(page);
+	__swapcache_free(entry, PageTransHuge(page));
+	page_ref_sub(page, hpage_nr_pages(page));
 }
 
 /* 
-- 
2.8.1

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#1478949 — Re: [PATCH -v3 07/10] mm, THP, swap: Support to add/delete THP to/from swap cache

On 09/07/2016 10:16 PM, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
> 
> With this patch, a THP (Transparent Huge Page) can be added/deleted
> to/from the swap cache as a set of sub-pages (512 on x86_64).
> 
> This will be used for the THP (Transparent Huge Page) swap support.
> Where one THP may be added/delted to/from the swap cache.  This will
> batch the swap cache operations to reduce the lock acquire/release times
> for the THP swap too.
> 
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Shaohua Li <shli@kernel.org>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> ---
>  include/linux/page-flags.h |  2 +-
>  mm/swap_state.c            | 57 +++++++++++++++++++++++++++++++---------------
>  2 files changed, 40 insertions(+), 19 deletions(-)
> 
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 74e4dda..f5bcbea 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -314,7 +314,7 @@ PAGEFLAG_FALSE(HighMem)
>  #endif
>  
>  #ifdef CONFIG_SWAP
> -PAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
> +PAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)

What is the reason for this change ? The commit message does not seem
to explain.

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#1479421 — Re: [PATCH -v3 07/10] mm, THP, swap: Support to add/delete THP to/from swap cache

Hi, Anshuman,

Thanks for comments!

Anshuman Khandual <khandual@linux.vnet.ibm.com> writes:

> On 09/07/2016 10:16 PM, Huang, Ying wrote:
>> From: Huang Ying <ying.huang@intel.com>
>> 
>> With this patch, a THP (Transparent Huge Page) can be added/deleted
>> to/from the swap cache as a set of sub-pages (512 on x86_64).
>> 
>> This will be used for the THP (Transparent Huge Page) swap support.
>> Where one THP may be added/delted to/from the swap cache.  This will
>> batch the swap cache operations to reduce the lock acquire/release times
>> for the THP swap too.
>> 
>> Cc: Hugh Dickins <hughd@google.com>
>> Cc: Shaohua Li <shli@kernel.org>
>> Cc: Minchan Kim <minchan@kernel.org>
>> Cc: Rik van Riel <riel@redhat.com>
>> Cc: Andrea Arcangeli <aarcange@redhat.com>
>> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>> ---
>>  include/linux/page-flags.h |  2 +-
>>  mm/swap_state.c            | 57 +++++++++++++++++++++++++++++++---------------
>>  2 files changed, 40 insertions(+), 19 deletions(-)
>> 
>> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
>> index 74e4dda..f5bcbea 100644
>> --- a/include/linux/page-flags.h
>> +++ b/include/linux/page-flags.h
>> @@ -314,7 +314,7 @@ PAGEFLAG_FALSE(HighMem)
>>  #endif
>>  
>>  #ifdef CONFIG_SWAP
>> -PAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
>> +PAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
>
> What is the reason for this change ? The commit message does not seem
> to explain.

Before this change, SetPageSwapCache() cannot be called for THP, after
the change, SetPageSwapCache() could be called for the head page of the
THP, but not the tail pages.  Because we will never do that before this
patch series.

Best Regards,
Huang, Ying

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#1479661 — Re: [PATCH -v3 00/10] THP swap: Delay splitting THP during swapping out

Hi Huang,

On Wed, Sep 07, 2016 at 09:45:59AM -0700, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
> 
> This patchset is to optimize the performance of Transparent Huge Page
> (THP) swap.
> 
> Hi, Andrew, could you help me to check whether the overall design is
> reasonable?
> 
> Hi, Hugh, Shaohua, Minchan and Rik, could you help me to review the
> swap part of the patchset?  Especially [01/10], [04/10], [05/10],
> [06/10], [07/10], [10/10].
> 
> Hi, Andrea and Kirill, could you help me to review the THP part of the
> patchset?  Especially [02/10], [03/10], [09/10] and [10/10].
> 
> Hi, Johannes, Michal and Vladimir, I am not very confident about the
> memory cgroup part, especially [02/10] and [03/10].  Could you help me
> to review it?
> 
> And for all, Any comment is welcome!
> 
> 
> Recently, the performance of the storage devices improved so fast that
> we cannot saturate the disk bandwidth when do page swap out even on a
> high-end server machine.  Because the performance of the storage
> device improved faster than that of CPU.  And it seems that the trend
> will not change in the near future.  On the other hand, the THP
> becomes more and more popular because of increased memory size.  So it
> becomes necessary to optimize THP swap performance.
> 
> The advantages of the THP swap support include:
> 
> - Batch the swap operations for the THP to reduce lock
>   acquiring/releasing, including allocating/freeing the swap space,
>   adding/deleting to/from the swap cache, and writing/reading the swap
>   space, etc.  This will help improve the performance of the THP swap.
> 
> - The THP swap space read/write will be 2M sequential IO.  It is
>   particularly helpful for the swap read, which usually are 4k random
>   IO.  This will improve the performance of the THP swap too.
> 
> - It will help the memory fragmentation, especially when the THP is
>   heavily used by the applications.  The 2M continuous pages will be
>   free up after THP swapping out.

I just read patchset right now and still doubt why the all changes
should be coupled with THP tightly. Many parts(e.g., you introduced
or modifying existing functions for making them THP specific) could
just take page_list and the number of pages then would handle them
without THP awareness.

For example, if the nr_pages is larger than SWAPFILE_CLUSTER, we
can try to allocate new cluster. With that, we could allocate new
clusters to meet nr_pages requested or bail out if we fail to allocate
and fallback to 0-order page swapout. With that, swap layer could
support multiple order-0 pages by batch.

IMO, I really want to land Tim Chen's batching swapout work first.
With Tim Chen's work, I expect we can make better refactoring
for batching swap before adding more confuse to the swap layer.
(I expect it would share several pieces of code for or would be base
for batching allocation of swapcache, swapslot)

After that, we could enhance swap for big contiguous batching
like THP and finally we might make it be aware of THP specific to
enhance further.

A thing I remember you aruged: you want to swapin 512 pages
all at once unconditionally. It's really worth to discuss if
your design is going for the way.
I doubt it's generally good idea. Because, currently, we try to
swap in swapped out pages in THP page with conservative approach
but your direction is going to opposite way.

[mm, thp: convert from optimistic swapin collapsing to conservative]

I think general approach(i.e., less effective than targeting
implement for your own specific goal but less hacky and better job
for many cases) is to rely/improve on the swap readahead.
If most of subpages of a THP page are really workingset, swap readahead
could work well.

Yeah, it's fairly vague feedback so sorry if I miss something clear.

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