2022-10-26 21:04:05

by Nhat Pham

Subject: [PATCH 3/5] zsmalloc: Add a LRU to zs_pool to keep track of zspages in LRU order

This helps determines the coldest zspages as candidates for writeback.

Signed-off-by: Nhat Pham <[email protected]>
---
mm/zsmalloc.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 326faa751f0a..600c40121544 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -239,6 +239,9 @@ struct zs_pool {
/* Compact classes */
struct shrinker shrinker;

+ /* List tracking the zspages in LRU order by most recently added object */
+ struct list_head lru;
+
#ifdef CONFIG_ZSMALLOC_STAT
struct dentry *stat_dentry;
#endif
@@ -260,6 +263,10 @@ struct zspage {
unsigned int freeobj;
struct page *first_page;
struct list_head list; /* fullness list */
+
+ /* links the zspage to the lru list in the pool */
+ struct list_head lru;
+
struct zs_pool *pool;
#ifdef CONFIG_COMPACTION
rwlock_t lock;
@@ -352,6 +359,16 @@ static void cache_free_zspage(struct zs_pool *pool, struct zspage *zspage)
kmem_cache_free(pool->zspage_cachep, zspage);
}

+/* Moves the zspage to the front of the zspool's LRU */
+static void move_to_front(struct zs_pool *pool, struct zspage *zspage)
+{
+ assert_spin_locked(&pool->lock);
+
+ if (!list_empty(&zspage->lru))
+ list_del(&zspage->lru);
+ list_add(&zspage->lru, &pool->lru);
+}
+
/* pool->lock(which owns the handle) synchronizes races */
static void record_obj(unsigned long handle, unsigned long obj)
{
@@ -953,6 +970,7 @@ static void free_zspage(struct zs_pool *pool, struct size_class *class,
}

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

@@ -998,6 +1016,8 @@ static void init_zspage(struct size_class *class, struct zspage *zspage)
off %= PAGE_SIZE;
}

+ INIT_LIST_HEAD(&zspage->lru);
+
set_freeobj(zspage, 0);
}

@@ -1418,6 +1438,8 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)
fix_fullness_group(class, zspage);
record_obj(handle, obj);
class_stat_inc(class, OBJ_USED, 1);
+ /* Move the zspage to front of pool's LRU */
+ move_to_front(pool, zspage);
spin_unlock(&pool->lock);

return handle;
@@ -1444,6 +1466,8 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)

/* We completely set up zspage so mark them as movable */
SetZsPageMovable(pool, zspage);
+ /* Move the zspage to front of pool's LRU */
+ move_to_front(pool, zspage);
spin_unlock(&pool->lock);

return handle;
@@ -1967,6 +1991,7 @@ 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);
+ list_del(&zspage->lru);
__free_zspage(pool, class, zspage);
spin_unlock(&pool->lock);
}
@@ -2278,6 +2303,8 @@ struct zs_pool *zs_create_pool(const char *name)
*/
zs_register_shrinker(pool);

+ INIT_LIST_HEAD(&pool->lru);
+
return pool;

err:
--
2.30.2

2022-10-28 15:06:57

by Johannes Weiner

Subject: Re: [PATCH 3/5] zsmalloc: Add a LRU to zs_pool to keep track of zspages in LRU order

On Wed, Oct 26, 2022 at 01:06:11PM -0700, Nhat Pham wrote:
> This helps determines the coldest zspages as candidates for writeback.
>
> Signed-off-by: Nhat Pham <[email protected]>

Acked-by: Johannes Weiner <[email protected]>