[RFC PATCH v2 1/6] slub: Keep track of whether slub is on the per-node partial list

chengming.zhou
2023-10-21T14:44:02Z

From: Chengming Zhou <zhouchengming@bytedance.com>

Now we rely on the "frozen" bit to see if we should manipulate the
slab->slab_list, which will be changed in the following patch.

Instead we introduce another way to keep track of whether slub is on
the per-node partial list, here we reuse the PG_workingset bit.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
---
include/linux/page-flags.h | 2 ++
mm/slab.h | 19 +++++++++++++++++++
mm/slub.c | 3 +++
3 files changed, 24 insertions(+)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index a88e64acebfe..e8b1be71d722 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -478,6 +478,8 @@ PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD)
TESTCLEARFLAG(Active, active, PF_HEAD)
PAGEFLAG(Workingset, workingset, PF_HEAD)
TESTCLEARFLAG(Workingset, workingset, PF_HEAD)
+ __SETPAGEFLAG(Workingset, workingset, PF_HEAD)
+ __CLEARPAGEFLAG(Workingset, workingset, PF_HEAD)
__PAGEFLAG(Slab, slab, PF_NO_TAIL)
PAGEFLAG(Checked, checked, PF_NO_COMPOUND) /* Used by some filesystems */

diff --git a/mm/slab.h b/mm/slab.h
index 8cd3294fedf5..9cff64cae8de 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -193,6 +193,25 @@ static inline void __slab_clear_pfmemalloc(struct slab *slab)
__folio_clear_active(slab_folio(slab));
}

+/*
+ * Slub reuse PG_workingset bit to keep track of whether it's on
+ * the per-node partial list.
+ */
+static inline bool slab_test_node_partial(const struct slab *slab)
+{
+ return folio_test_workingset((struct folio *)slab_folio(slab));
+}
+
+static inline void slab_set_node_partial(struct slab *slab)
+{
+ __folio_set_workingset(slab_folio(slab));
+}
+
+static inline void slab_clear_node_partial(struct slab *slab)
+{
+ __folio_clear_workingset(slab_folio(slab));
+}
+
static inline void *slab_address(const struct slab *slab)
{
return folio_address(slab_folio(slab));
diff --git a/mm/slub.c b/mm/slub.c
index 63d281dfacdb..3fad4edca34b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2127,6 +2127,7 @@ __add_partial(struct kmem_cache_node *n, struct slab *slab, int tail)
list_add_tail(&slab->slab_list, &n->partial);
else
list_add(&slab->slab_list, &n->partial);
+ slab_set_node_partial(slab);
}

static inline void add_partial(struct kmem_cache_node *n,
@@ -2141,6 +2142,7 @@ static inline void remove_partial(struct kmem_cache_node *n,
{
lockdep_assert_held(&n->list_lock);
list_del(&slab->slab_list);
+ slab_clear_node_partial(slab);
n->nr_partial--;
}

@@ -4831,6 +4833,7 @@ static int __kmem_cache_do_shrink(struct kmem_cache *s)

if (free == slab->objects) {
list_move(&slab->slab_list, &discard);
+ slab_clear_node_partial(slab);
n->nr_partial--;
dec_slabs_node(s, node, slab->objects);
} else if (free <= SHRINK_PROMOTE_MAX)
--
2.20.1