[PATCH v2 7/9] mm/swap: implement workingset detection for anonymous LRU

[js1304]

From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

This patch implements workingset detection for anonymous LRU.
All the infrastructure is implemented by the previous patches so this patch
just activates the workingset detection by installing/retrieving
the shadow entry.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
---
 include/linux/swap.h | 11 +++++++++--
 mm/memory.c          |  7 ++++++-
 mm/shmem.c           |  3 ++-
 mm/swap_state.c      | 31 ++++++++++++++++++++++++++-----
 mm/vmscan.c          |  7 +++++--
 5 files changed, 48 insertions(+), 11 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 0df8b3f..fb4772e 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -408,7 +408,9 @@ extern struct address_space *swapper_spaces[];
 extern unsigned long total_swapcache_pages(void);
 extern void show_swap_cache_info(void);
 extern int add_to_swap(struct page *page);
-extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
+extern void *get_shadow_from_swap_cache(swp_entry_t entry);
+extern int add_to_swap_cache(struct page *page, swp_entry_t entry,
+			gfp_t gfp, void **shadowp);
 extern int __add_to_swap_cache(struct page *page, swp_entry_t entry);
 extern void __delete_from_swap_cache(struct page *page,
 			swp_entry_t entry, void *shadow);
@@ -565,8 +567,13 @@ static inline int add_to_swap(struct page *page)
 	return 0;
 }
 
+static inline void *get_shadow_from_swap_cache(swp_entry_t entry)
+{
+	return NULL;
+}
+
 static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
-							gfp_t gfp_mask)
+					gfp_t gfp_mask, void **shadowp)
 {
 	return -1;
 }
diff --git a/mm/memory.c b/mm/memory.c
index 5f7813a..91a2097 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2925,10 +2925,15 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 			page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma,
 							vmf->address);
 			if (page) {
+				void *shadow;
+
 				__SetPageLocked(page);
 				__SetPageSwapBacked(page);
 				set_page_private(page, entry.val);
-				lru_cache_add_anon(page);
+				shadow = get_shadow_from_swap_cache(entry);
+				if (shadow)
+					workingset_refault(page, shadow);
+				lru_cache_add(page);
 				swap_readpage(page, true);
 			}
 		} else {
diff --git a/mm/shmem.c b/mm/shmem.c
index 8793e8c..c6663ad 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1370,7 +1370,8 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 		list_add(&info->swaplist, &shmem_swaplist);
 
 	if (add_to_swap_cache(page, swap,
-			__GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN) == 0) {
+			__GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN,
+			NULL) == 0) {
 		spin_lock_irq(&info->lock);
 		shmem_recalc_inode(inode);
 		info->swapped++;
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 3fbbe45..7f7cb19 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -107,11 +107,24 @@ void show_swap_cache_info(void)
 	printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
 }
 
+void *get_shadow_from_swap_cache(swp_entry_t entry)
+{
+	struct address_space *address_space = swap_address_space(entry);
+	pgoff_t idx = swp_offset(entry);
+	struct page *page;
+
+	page = find_get_entry(address_space, idx);
+	if (xa_is_value(page))
+		return page;
+	return NULL;
+}
+
 /*
  * add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
  * but sets SwapCache flag and private instead of mapping and index.
  */
-int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp)
+int add_to_swap_cache(struct page *page, swp_entry_t entry,
+			gfp_t gfp, void **shadowp)
 {
 	struct address_space *address_space = swap_address_space(entry);
 	pgoff_t idx = swp_offset(entry);
@@ -137,8 +150,11 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp)
 		for (i = 0; i < nr; i++) {
 			VM_BUG_ON_PAGE(xas.xa_index != idx + i, page);
 			old = xas_load(&xas);
-			if (xa_is_value(old))
+			if (xa_is_value(old)) {
 				nrexceptional++;
+				if (shadowp)
+					*shadowp = old;
+			}
 			set_page_private(page + i, entry.val + i);
 			xas_store(&xas, page);
 			xas_next(&xas);
@@ -226,7 +242,7 @@ int add_to_swap(struct page *page)
 	 * Add it to the swap cache.
 	 */
 	err = add_to_swap_cache(page, entry,
-			__GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);
+			__GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN, NULL);
 	if (err)
 		/*
 		 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
@@ -380,6 +396,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 	struct page *found_page = NULL, *new_page = NULL;
 	struct swap_info_struct *si;
 	int err;
+	void *shadow;
 	*new_page_allocated = false;
 
 	do {
@@ -435,11 +452,15 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 		/* May fail (-ENOMEM) if XArray node allocation failed. */
 		__SetPageLocked(new_page);
 		__SetPageSwapBacked(new_page);
-		err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
+		shadow = NULL;
+		err = add_to_swap_cache(new_page, entry,
+				gfp_mask & GFP_KERNEL, &shadow);
 		if (likely(!err)) {
 			/* Initiate read into locked page */
 			SetPageWorkingset(new_page);
-			lru_cache_add_anon(new_page);
+			if (shadow)
+				workingset_refault(new_page, shadow);
+			lru_cache_add(new_page);
 			*new_page_allocated = true;
 			return new_page;
 		}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 99588ba..a1892e7 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -867,6 +867,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
 {
 	unsigned long flags;
 	int refcount;
+	void *shadow = NULL;
 
 	BUG_ON(!PageLocked(page));
 	BUG_ON(mapping != page_mapping(page));
@@ -909,12 +910,13 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
 	if (PageSwapCache(page)) {
 		swp_entry_t swap = { .val = page_private(page) };
 		mem_cgroup_swapout(page, swap);
-		__delete_from_swap_cache(page, swap, NULL);
+		if (reclaimed && !mapping_exiting(mapping))
+			shadow = workingset_eviction(page, target_memcg);
+		__delete_from_swap_cache(page, swap, shadow);
 		xa_unlock_irqrestore(&mapping->i_pages, flags);
 		put_swap_page(page, swap);
 	} else {
 		void (*freepage)(struct page *);
-		void *shadow = NULL;
 
 		freepage = mapping->a_ops->freepage;
 		/*
@@ -1485,6 +1487,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 			SetPageActive(page);
 			stat->nr_activate[type] += nr_pages;
 			count_memcg_page_event(page, PGACTIVATE);
+			workingset_activation(page);
 		}
 keep_locked:
 		unlock_page(page);
-- 
2.7.4