From 8a399e2f60037ed07a55278e39b20e43dea4f0c2 Mon Sep 17 00:00:00 2001 From: Chengming Zhou Date: Thu, 2 Nov 2023 03:23:24 +0000 Subject: [PATCH] slub: Keep track of whether slub is on the per-node partial list 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. We have to use the atomic set_bit() and clear_bit() variants and change slab_unlock() to bit_spin_unlock() because when cmpxchg is not available and PG_lock is used, there may be concurrent operations on the two bits. Thanks to Mark Brown for reporting a hang and testing of a previous version where the non-atomic operations were used. Suggested-by: Matthew Wilcox Signed-off-by: Chengming Zhou Reviewed-by: Vlastimil Babka Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Signed-off-by: Vlastimil Babka --- mm/slub.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/mm/slub.c b/mm/slub.c index 03384cd965c5..6efcbf79fd2d 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -522,7 +522,7 @@ static __always_inline void slab_unlock(struct slab *slab) struct page *page = slab_page(slab); VM_BUG_ON_PAGE(PageTail(page), page); - __bit_spin_unlock(PG_locked, &page->flags); + bit_spin_unlock(PG_locked, &page->flags); } static inline bool @@ -2116,6 +2116,25 @@ static void discard_slab(struct kmem_cache *s, struct slab *slab) free_slab(s, slab); } +/* + * SLUB reuses 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) +{ + set_bit(PG_workingset, folio_flags(slab_folio(slab), 0)); +} + +static inline void slab_clear_node_partial(struct slab *slab) +{ + clear_bit(PG_workingset, folio_flags(slab_folio(slab), 0)); +} + /* * Management of partially allocated slabs. */ @@ -2127,6 +2146,7 @@ __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 +2161,7 @@ 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--; } @@ -4833,6 +4854,7 @@ 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)