[PATCH v8 6/6] zswap: shrinks zswap pool based on memory pressure (fix)

Nhat Pham
2023-12-06T19:45:02Z

Check shrinker enablement early, and use a less costly stat flushing.

Suggested-by: Yosry Ahmed <yosryahmed@google.com>
Suggested-by: Chengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
---
mm/zswap.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 27c749f6c1ba..d8ecd79120f3 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -596,13 +596,17 @@ static unsigned long zswap_shrinker_scan(struct shrinker *shrinker,
struct zswap_pool *pool = shrinker->private_data;
bool encountered_page_in_swapcache = false;

+ if (!zswap_shrinker_enabled) {
+ sc->nr_scanned = 0;
+ return SHRINK_STOP;
+ }
+
nr_protected =
atomic_long_read(&lruvec->zswap_lruvec_state.nr_zswap_protected);
lru_size = list_lru_shrink_count(&pool->list_lru, sc);

/*
- * Abort if the shrinker is disabled or if we are shrinking into the
- * protected region.
+ * Abort if we are shrinking into the protected region.
*
* This short-circuiting is necessary because if we have too many multiple
* concurrent reclaimers getting the freeable zswap object counts at the
@@ -611,7 +615,7 @@ static unsigned long zswap_shrinker_scan(struct shrinker *shrinker,
* objects (i.e the reclaimers will reclaim into the protected area of the
* zswap LRU).
*/
- if (!zswap_shrinker_enabled || nr_protected >= lru_size - sc->nr_to_scan) {
+ if (nr_protected >= lru_size - sc->nr_to_scan) {
sc->nr_scanned = 0;
return SHRINK_STOP;
}
@@ -633,8 +637,11 @@ static unsigned long zswap_shrinker_count(struct shrinker *shrinker,
struct lruvec *lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(sc->nid));
unsigned long nr_backing, nr_stored, nr_freeable, nr_protected;

+ if (!zswap_shrinker_enabled)
+ return 0;
+
#ifdef CONFIG_MEMCG_KMEM
- cgroup_rstat_flush(memcg->css.cgroup);
+ mem_cgroup_flush_stats();
nr_backing = memcg_page_state(memcg, MEMCG_ZSWAP_B) >> PAGE_SHIFT;
nr_stored = memcg_page_state(memcg, MEMCG_ZSWAPPED);
#else
@@ -643,7 +650,7 @@ static unsigned long zswap_shrinker_count(struct shrinker *shrinker,
nr_stored = atomic_read(&pool->nr_stored);
#endif

- if (!zswap_shrinker_enabled || !nr_stored)
+ if (!nr_stored)
return 0;

nr_protected =
--
2.34.1