[PATCH] mm/zsmalloc: disclose statistics to debugfs

[Ganesh Mahendran]

As we now talk more and more about the fragmentation of zsmalloc. But
we still need to manually add some debug code to see the fragmentation.
So, I think we may add the statistics of memory fragmention in zsmalloc
and disclose them to debugfs. Then we can easily get and analysis
them when adding or developing new feature for zsmalloc.

Below entries will be created when a zsmalloc pool is created:
    /sys/kernel/debug/zsmalloc/pool-n/obj_allocated
    /sys/kernel/debug/zsmalloc/pool-n/obj_used

Then the status of objects usage will be:
    objects_usage = obj_used / obj_allocated

Also we can collect other information and add corresponding entries
in debugfs when needed.

Signed-off-by: Ganesh Mahendran <opensource.ganesh@xxxxxxxxx>
---
 mm/zsmalloc.c |  108 ++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 104 insertions(+), 4 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 4d0a063..f682ef9 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -168,6 +168,8 @@ enum fullness_group {
 	ZS_FULL
 };
 
+static int zs_pool_num;
+
 /*
  * number of size_classes
  */
@@ -216,11 +218,19 @@ struct link_free {
 	void *next;
 };
 
+struct zs_stats {
+	atomic_long_t pages_allocated;
+	u64 obj_allocated;
+	u64 obj_used;
+};
+
 struct zs_pool {
 	struct size_class **size_class;
 
 	gfp_t flags;	/* allocation flags used when growing pool */
-	atomic_long_t pages_allocated;
+
+	struct zs_stats stats;
+	struct dentry *debugfs_dentry;
 };
 
 /*
@@ -925,12 +935,84 @@ static void init_zs_size_classes(void)
 	zs_size_classes = nr;
 }
 
+
+#ifdef CONFIG_DEBUG_FS
+#include <linux/debugfs.h>
+
+static struct dentry *zs_debugfs_root;
+
+static int __init zs_debugfs_init(void)
+{
+	if (!debugfs_initialized())
+		return -ENODEV;
+
+	zs_debugfs_root = debugfs_create_dir("zsmalloc", NULL);
+	if (!zs_debugfs_root)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void __exit zs_debugfs_exit(void)
+{
+	debugfs_remove_recursive(zs_debugfs_root);
+}
+
+static int zs_pool_debugfs_create(struct zs_pool *pool, int index)
+{
+	char name[10];
+	int ret = 0;
+
+	if (!zs_debugfs_root) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	snprintf(name, sizeof(name), "pool-%d", index);
+	pool->debugfs_dentry = debugfs_create_dir(name, zs_debugfs_root);
+	if (!pool->debugfs_dentry) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	debugfs_create_u64("obj_allocated", S_IRUGO, pool->debugfs_dentry,
+			&pool->stats.obj_allocated);
+	debugfs_create_u64("obj_used", S_IRUGO, pool->debugfs_dentry,
+			&pool->stats.obj_used);
+
+out:
+	return ret;
+}
+
+static void zs_pool_debugfs_destroy(struct zs_pool *pool)
+{
+	debugfs_remove_recursive(pool->debugfs_dentry);
+}
+
+#else
+static int __init zs_debugfs_init(void)
+{
+	return 0;
+}
+
+static void __exit zs_debugfs_exit(void) { }
+
+static int zs_pool_debugfs_create(struct zs_pool *pool, int index)
+{
+	return 0;
+}
+
+static void zs_pool_debugfs_destroy(struct zs_pool *pool) {}
+#endif
+
 static void __exit zs_exit(void)
 {
 #ifdef CONFIG_ZPOOL
 	zpool_unregister_driver(&zs_zpool_driver);
 #endif
 	zs_unregister_cpu_notifier();
+
+	zs_debugfs_exit();
 }
 
 static int __init zs_init(void)
@@ -947,6 +1029,10 @@ static int __init zs_init(void)
 #ifdef CONFIG_ZPOOL
 	zpool_register_driver(&zs_zpool_driver);
 #endif
+
+	if (zs_debugfs_init())
+		pr_warn("debugfs initialization failed\n");
+
 	return 0;
 }
 
@@ -1039,6 +1125,11 @@ struct zs_pool *zs_create_pool(gfp_t flags)
 
 	pool->flags = flags;
 
+	zs_pool_num++;
+
+	if (zs_pool_debugfs_create(pool, zs_pool_num))
+		pr_warn("zs pool debugfs initialization failed\n");
+
 	return pool;
 
 err:
@@ -1071,6 +1162,9 @@ void zs_destroy_pool(struct zs_pool *pool)
 	}
 
 	kfree(pool->size_class);
+	zs_pool_debugfs_destroy(pool);
+	zs_pool_num--;
+
 	kfree(pool);
 }
 EXPORT_SYMBOL_GPL(zs_destroy_pool);
@@ -1110,7 +1204,9 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
 
 		set_zspage_mapping(first_page, class->index, ZS_EMPTY);
 		atomic_long_add(class->pages_per_zspage,
-					&pool->pages_allocated);
+					&pool->stats.pages_allocated);
+		pool->stats.obj_allocated += get_maxobj_per_zspage(class->size,
+				class->pages_per_zspage);
 		spin_lock(&class->lock);
 	}
 
@@ -1125,6 +1221,7 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
 	kunmap_atomic(vaddr);
 
 	first_page->inuse++;
+	pool->stats.obj_used++;
 	/* Now move the zspage to another fullness group, if required */
 	fix_fullness_group(pool, first_page);
 	spin_unlock(&class->lock);
@@ -1164,12 +1261,15 @@ void zs_free(struct zs_pool *pool, unsigned long obj)
 	first_page->freelist = (void *)obj;
 
 	first_page->inuse--;
+	pool->stats.obj_used--;
 	fullness = fix_fullness_group(pool, first_page);
 	spin_unlock(&class->lock);
 
 	if (fullness == ZS_EMPTY) {
 		atomic_long_sub(class->pages_per_zspage,
-				&pool->pages_allocated);
+				&pool->stats.pages_allocated);
+		pool->stats.obj_allocated -= get_maxobj_per_zspage(class->size,
+				class->pages_per_zspage);
 		free_zspage(first_page);
 	}
 }
@@ -1267,7 +1367,7 @@ EXPORT_SYMBOL_GPL(zs_unmap_object);
 
 unsigned long zs_get_total_pages(struct zs_pool *pool)
 {
-	return atomic_long_read(&pool->pages_allocated);
+	return atomic_long_read(&pool->stats.pages_allocated);
 }
 EXPORT_SYMBOL_GPL(zs_get_total_pages);
 
-- 
1.7.9.5

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