[RFC v1 5/6] gcma: export statistical data on debugfs

[SeongJae Park <sj38.park@gmail.com>]

Export saved / loaded / evicted / reclaimed pages from gcma's frontswap
backend on debugfs to let users know how gcma is working internally.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
---
 mm/gcma.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/mm/gcma.c b/mm/gcma.c
index 9c07128..65395ec 100644
--- a/mm/gcma.c
+++ b/mm/gcma.c
@@ -57,6 +57,12 @@ static spinlock_t slru_lock;	/* protect slru_list */
 static struct frontswap_tree *gcma_swap_trees[MAX_SWAPFILES];
 static struct kmem_cache *swap_slot_entry_cache;
 
+/* For statistics */
+static atomic_t gcma_stored_pages = ATOMIC_INIT(0);
+static atomic_t gcma_loaded_pages = ATOMIC_INIT(0);
+static atomic_t gcma_evicted_pages = ATOMIC_INIT(0);
+static atomic_t gcma_reclaimed_pages = ATOMIC_INIT(0);
+
 static unsigned long evict_frontswap_pages(unsigned long nr_pages);
 
 static struct frontswap_tree *swap_tree(struct page *page)
@@ -380,6 +386,7 @@ static unsigned long evict_frontswap_pages(unsigned long nr_pages)
 		spin_unlock(&tree->lock);
 	}
 
+	atomic_add(evicted, &gcma_evicted_pages);
 	return evicted;
 }
 
@@ -480,6 +487,7 @@ int gcma_frontswap_store(unsigned type, pgoff_t offset,
 	spin_unlock(&slru_lock);
 	spin_unlock(&tree->lock);
 
+	atomic_inc(&gcma_stored_pages);
 	return ret;
 }
 
@@ -521,6 +529,7 @@ int gcma_frontswap_load(unsigned type, pgoff_t offset,
 	spin_unlock(&slru_lock);
 	spin_unlock(&tree->lock);
 
+	atomic_inc(&gcma_loaded_pages);
 	return 0;
 }
 
@@ -659,6 +668,7 @@ retry:
 			if (atomic_inc_not_zero(&entry->refcount)) {
 				clear_gpage_flag(page, GF_SWAP_LRU);
 				set_gpage_flag(page, GF_RECLAIMING);
+				atomic_inc(&gcma_reclaimed_pages);
 				list_move(&page->lru, &free_pages);
 				spin_unlock(&slru_lock);
 				continue;
@@ -679,6 +689,7 @@ retry:
 			set_gpage_flag(page, GF_ISOLATED);
 		} else {
 			set_gpage_flag(page, GF_RECLAIMING);
+			atomic_inc(&gcma_reclaimed_pages);
 		}
 		spin_unlock(&gcma->lock);
 		spin_unlock(&slru_lock);
@@ -727,6 +738,40 @@ void gcma_free_contig(struct gcma *gcma,
 	spin_unlock(&gcma->lock);
 }
 
+#ifdef CONFIG_DEBUG_FS
+#include <linux/debugfs.h>
+
+static struct dentry *gcma_debugfs_root;
+
+static int __init gcma_debugfs_init(void)
+{
+	if (!debugfs_initialized())
+		return -ENODEV;
+
+	gcma_debugfs_root = debugfs_create_dir("gcma", NULL);
+	if (!gcma_debugfs_root)
+		return -ENOMEM;
+
+	debugfs_create_atomic_t("stored_pages", S_IRUGO,
+			gcma_debugfs_root, &gcma_stored_pages);
+	debugfs_create_atomic_t("loaded_pages", S_IRUGO,
+			gcma_debugfs_root, &gcma_loaded_pages);
+	debugfs_create_atomic_t("evicted_pages", S_IRUGO,
+			gcma_debugfs_root, &gcma_evicted_pages);
+	debugfs_create_atomic_t("reclaimed_pages", S_IRUGO,
+			gcma_debugfs_root, &gcma_reclaimed_pages);
+
+	pr_info("gcma debufs init\n");
+	return 0;
+}
+#else
+static int __init gcma_debugfs_init(void)
+{
+	return 0;
+}
+#endif
+
+
 static int __init init_gcma(void)
 {
 	pr_info("loading gcma\n");
@@ -743,6 +788,7 @@ static int __init init_gcma(void)
 	frontswap_writethrough(true);
 	frontswap_register_ops(&gcma_frontswap_ops);
 
+	gcma_debugfs_init();
 	return 0;
 }
 
-- 
1.9.1

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