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authorChengming Zhou <zhouchengming@bytedance.com>2024-02-16 08:55:05 +0000
committerAndrew Morton <akpm@linux-foundation.org>2024-03-04 17:01:13 -0800
commit94ace3fec8477f8a46d08fc57cd1dd5efbd0a32b (patch)
treeac179b460545096cbd441a2c165260f6ed5d83c5 /mm/zswap.c
parentbf9b7df23cb3c03d8cdbcaa58817e60ce06105ac (diff)
mm/zswap: change zswap_pool kref to percpu_ref
All zswap entries will take a reference of zswap_pool when zswap_store(), and drop it when free. Change it to use the percpu_ref is better for scalability performance. Although percpu_ref use a bit more memory which should be ok for our use case, since we almost have only one zswap_pool to be using. The performance gain is for zswap_store/load hotpath. Testing kernel build (32 threads) in tmpfs with memory.max=2GB. (zswap shrinker and writeback enabled with one 50GB swapfile, on a 128 CPUs x86-64 machine, below is the average of 5 runs) mm-unstable zswap-global-lru real 63.20 63.12 user 1061.75 1062.95 sys 268.74 264.44 [chengming.zhou@linux.dev: fix zswap_pools_lock usages after changing to percpu_ref] Link: https://lkml.kernel.org/r/20240228154954.3028626-1-chengming.zhou@linux.dev Link: https://lkml.kernel.org/r/20240210-zswap-global-lru-v3-2-200495333595@bytedance.com Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> Reviewed-by: Nhat Pham <nphamcs@gmail.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Chengming Zhou <chengming.zhou@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/zswap.c')
-rw-r--r--mm/zswap.c48
1 files changed, 33 insertions, 15 deletions
diff --git a/mm/zswap.c b/mm/zswap.c
index 0141c45a5a6f..da90933c6d20 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -173,7 +173,7 @@ struct crypto_acomp_ctx {
struct zswap_pool {
struct zpool *zpools[ZSWAP_NR_ZPOOLS];
struct crypto_acomp_ctx __percpu *acomp_ctx;
- struct kref kref;
+ struct percpu_ref ref;
struct list_head list;
struct work_struct release_work;
struct hlist_node node;
@@ -305,6 +305,7 @@ static void zswap_update_total_size(void)
/*********************************
* pool functions
**********************************/
+static void __zswap_pool_empty(struct percpu_ref *ref);
static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
{
@@ -358,13 +359,18 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
/* being the current pool takes 1 ref; this func expects the
* caller to always add the new pool as the current pool
*/
- kref_init(&pool->kref);
+ ret = percpu_ref_init(&pool->ref, __zswap_pool_empty,
+ PERCPU_REF_ALLOW_REINIT, GFP_KERNEL);
+ if (ret)
+ goto ref_fail;
INIT_LIST_HEAD(&pool->list);
zswap_pool_debug("created", pool);
return pool;
+ref_fail:
+ cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
error:
if (pool->acomp_ctx)
free_percpu(pool->acomp_ctx);
@@ -437,8 +443,9 @@ static void __zswap_pool_release(struct work_struct *work)
synchronize_rcu();
- /* nobody should have been able to get a kref... */
- WARN_ON(kref_get_unless_zero(&pool->kref));
+ /* nobody should have been able to get a ref... */
+ WARN_ON(!percpu_ref_is_zero(&pool->ref));
+ percpu_ref_exit(&pool->ref);
/* pool is now off zswap_pools list and has no references. */
zswap_pool_destroy(pool);
@@ -446,13 +453,13 @@ static void __zswap_pool_release(struct work_struct *work)
static struct zswap_pool *zswap_pool_current(void);
-static void __zswap_pool_empty(struct kref *kref)
+static void __zswap_pool_empty(struct percpu_ref *ref)
{
struct zswap_pool *pool;
- pool = container_of(kref, typeof(*pool), kref);
+ pool = container_of(ref, typeof(*pool), ref);
- spin_lock(&zswap_pools_lock);
+ spin_lock_bh(&zswap_pools_lock);
WARN_ON(pool == zswap_pool_current());
@@ -461,7 +468,7 @@ static void __zswap_pool_empty(struct kref *kref)
INIT_WORK(&pool->release_work, __zswap_pool_release);
schedule_work(&pool->release_work);
- spin_unlock(&zswap_pools_lock);
+ spin_unlock_bh(&zswap_pools_lock);
}
static int __must_check zswap_pool_get(struct zswap_pool *pool)
@@ -469,12 +476,12 @@ static int __must_check zswap_pool_get(struct zswap_pool *pool)
if (!pool)
return 0;
- return kref_get_unless_zero(&pool->kref);
+ return percpu_ref_tryget(&pool->ref);
}
static void zswap_pool_put(struct zswap_pool *pool)
{
- kref_put(&pool->kref, __zswap_pool_empty);
+ percpu_ref_put(&pool->ref);
}
static struct zswap_pool *__zswap_pool_current(void)
@@ -591,7 +598,7 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp,
return -EINVAL;
}
- spin_lock(&zswap_pools_lock);
+ spin_lock_bh(&zswap_pools_lock);
pool = zswap_pool_find_get(type, compressor);
if (pool) {
@@ -600,17 +607,28 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp,
list_del_rcu(&pool->list);
}
- spin_unlock(&zswap_pools_lock);
+ spin_unlock_bh(&zswap_pools_lock);
if (!pool)
pool = zswap_pool_create(type, compressor);
+ else {
+ /*
+ * Restore the initial ref dropped by percpu_ref_kill()
+ * when the pool was decommissioned and switch it again
+ * to percpu mode.
+ */
+ percpu_ref_resurrect(&pool->ref);
+
+ /* Drop the ref from zswap_pool_find_get(). */
+ zswap_pool_put(pool);
+ }
if (pool)
ret = param_set_charp(s, kp);
else
ret = -EINVAL;
- spin_lock(&zswap_pools_lock);
+ spin_lock_bh(&zswap_pools_lock);
if (!ret) {
put_pool = zswap_pool_current();
@@ -625,7 +643,7 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp,
put_pool = pool;
}
- spin_unlock(&zswap_pools_lock);
+ spin_unlock_bh(&zswap_pools_lock);
if (!zswap_has_pool && !pool) {
/* if initial pool creation failed, and this pool creation also
@@ -642,7 +660,7 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp,
* or the new pool we failed to add
*/
if (put_pool)
- zswap_pool_put(put_pool);
+ percpu_ref_kill(&put_pool->ref);
return ret;
}