[PATCH v6 4/6] zsmalloc: Add a LRU to zs_pool to keep track of zspages in LRU order

From: Nhat Pham
Date: Fri Nov 18 2022 - 20:19:14 EST


This helps determines the coldest zspages as candidates for writeback.

Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx>
---
mm/zsmalloc.c | 34 ++++++++++++++++++++++++++++++++++
1 file changed, 34 insertions(+)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 326faa751f0a..7dd464b5a6a5 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -239,6 +239,11 @@ struct zs_pool {
/* Compact classes */
struct shrinker shrinker;

+#ifdef CONFIG_ZPOOL
+ /* List tracking the zspages in LRU order by most recently added object */
+ struct list_head lru;
+#endif
+
#ifdef CONFIG_ZSMALLOC_STAT
struct dentry *stat_dentry;
#endif
@@ -260,6 +265,12 @@ struct zspage {
unsigned int freeobj;
struct page *first_page;
struct list_head list; /* fullness list */
+
+#ifdef CONFIG_ZPOOL
+ /* links the zspage to the lru list in the pool */
+ struct list_head lru;
+#endif
+
struct zs_pool *pool;
#ifdef CONFIG_COMPACTION
rwlock_t lock;
@@ -953,6 +964,9 @@ static void free_zspage(struct zs_pool *pool, struct size_class *class,
}

remove_zspage(class, zspage, ZS_EMPTY);
+#ifdef CONFIG_ZPOOL
+ list_del(&zspage->lru);
+#endif
__free_zspage(pool, class, zspage);
}

@@ -998,6 +1012,10 @@ static void init_zspage(struct size_class *class, struct zspage *zspage)
off %= PAGE_SIZE;
}

+#ifdef CONFIG_ZPOOL
+ INIT_LIST_HEAD(&zspage->lru);
+#endif
+
set_freeobj(zspage, 0);
}

@@ -1249,6 +1267,15 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle,
obj_to_location(obj, &page, &obj_idx);
zspage = get_zspage(page);

+#ifdef CONFIG_ZPOOL
+ /* Move the zspage to front of pool's LRU */
+ if (mm == ZS_MM_WO) {
+ if (!list_empty(&zspage->lru))
+ list_del(&zspage->lru);
+ list_add(&zspage->lru, &pool->lru);
+ }
+#endif
+
/*
* migration cannot move any zpages in this zspage. Here, pool->lock
* is too heavy since callers would take some time until they calls
@@ -1967,6 +1994,9 @@ static void async_free_zspage(struct work_struct *work)
VM_BUG_ON(fullness != ZS_EMPTY);
class = pool->size_class[class_idx];
spin_lock(&pool->lock);
+#ifdef CONFIG_ZPOOL
+ list_del(&zspage->lru);
+#endif
__free_zspage(pool, class, zspage);
spin_unlock(&pool->lock);
}
@@ -2278,6 +2308,10 @@ struct zs_pool *zs_create_pool(const char *name)
*/
zs_register_shrinker(pool);

+#ifdef CONFIG_ZPOOL
+ INIT_LIST_HEAD(&pool->lru);
+#endif
+
return pool;

err:
--
2.30.2