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.
Link: https://lkml.kernel.org/r/20221128191616.1261026-5-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 5427a00..b1bc231 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);
}
@@ -1270,6 +1288,31 @@ 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.
+ *
+ * Note that this is swap-specific, so by definition there are no ongoing
+ * accesses to the memory while the page is swapped out that would make
+ * it "hot". A new entry is hot, then ages to the tail until it gets either
+ * written back or swaps back in.
+ *
+ * Furthermore, map is also called during writeback. We must not put an
+ * isolated page on the LRU mid-reclaim.
+ *
+ * As a result, only update the LRU when the page is mapped for write
+ * when it's first instantiated.
+ *
+ * This is a deviation from the other backends, which perform this update
+ * in the allocation function (zbud_alloc, z3fold_alloc).
+ */
+ 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
@@ -1988,6 +2031,9 @@ 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);
}
@@ -2299,6 +2345,10 @@ 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:
