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Howlett" , Usama Arif , Kiryl Shutsemau , Dave Chinner , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 7/7] mm: switch deferred split shrinker to list_lru Message-ID: References: <20260312205321.638053-1-hannes@cmpxchg.org> <20260312205321.638053-8-hannes@cmpxchg.org> <61d86249-cd89-4e99-99d8-ab7c72e95f34@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Mar 19, 2026 at 08:21:21AM +0100, David Hildenbrand (Arm) wrote: > Of course :) If list_lru lock helpers would be the right thing to do, it > might be better placed in this series. I think this is slightly more promising. See below. The callsites in huge_memory.c look nicer. But the double folio_nid() and folio_memcg() lookups (when the caller needs them too) are kind of unfortunate; and it feels like a lot of API for 4 callsites. Thoughts? include/linux/list_lru.h | 8 ++++++++ mm/huge_memory.c | 43 +++++++++++++++---------------------------- mm/list_lru.c | 29 +++++++++++++++++++++++++++++ 3 files changed, 52 insertions(+), 28 deletions(-) diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h index 4bd29b61c59a..6b734d08fa1b 100644 --- a/include/linux/list_lru.h +++ b/include/linux/list_lru.h @@ -123,6 +123,14 @@ struct list_lru_one *list_lru_lock_irqsave(struct list_lru *lru, int nid, void list_lru_unlock_irqrestore(struct list_lru_one *l, unsigned long *irq_flags); +struct list_lru_one *folio_list_lru_lock(struct folio *folio, + struct list_lru *lru); +void folio_list_lru_unlock(struct folio *folio, struct list_lru_one *l); +struct list_lru_one *folio_list_lru_lock_irqsave(struct folio *folio, + struct list_lru *lru, unsigned long *flags); +void folio_list_lru_unlock_irqrestore(struct folio *folio, + struct list_lru_one *l, unsigned long *flags); + /* Caller-locked variants, see list_lru_add() etc for documentation */ bool __list_lru_add(struct list_lru *lru, struct list_lru_one *l, struct list_head *item, int nid, struct mem_cgroup *memcg); diff --git a/mm/huge_memory.c b/mm/huge_memory.c index e90d08db219d..6996ef224e24 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3768,11 +3768,8 @@ static int __folio_freeze_and_split_unmapped(struct folio *folio, unsigned int n VM_WARN_ON_ONCE(!mapping && end); /* Prevent deferred_split_scan() touching ->_refcount */ dequeue_deferred = folio_test_anon(folio) && old_order > 1; - if (dequeue_deferred) { - rcu_read_lock(); - l = list_lru_lock(&deferred_split_lru, - folio_nid(folio), folio_memcg(folio)); - } + if (dequeue_deferred) + l = folio_list_lru_lock(folio, &deferred_split_lru); if (folio_ref_freeze(folio, folio_cache_ref_count(folio) + 1)) { struct swap_cluster_info *ci = NULL; struct lruvec *lruvec; @@ -3785,8 +3782,7 @@ static int __folio_freeze_and_split_unmapped(struct folio *folio, unsigned int n mod_mthp_stat(old_order, MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1); } - list_lru_unlock(l); - rcu_read_unlock(); + folio_list_lru_unlock(folio, l); } if (mapping) { @@ -3889,10 +3885,8 @@ static int __folio_freeze_and_split_unmapped(struct folio *folio, unsigned int n if (ci) swap_cluster_unlock(ci); } else { - if (dequeue_deferred) { - list_lru_unlock(l); - rcu_read_unlock(); - } + if (dequeue_deferred) + folio_list_lru_unlock(folio, l); return -EAGAIN; } @@ -4276,8 +4270,7 @@ bool __folio_unqueue_deferred_split(struct folio *folio) WARN_ON_ONCE(folio_ref_count(folio)); WARN_ON_ONCE(!mem_cgroup_disabled() && !folio_memcg_charged(folio)); - rcu_read_lock(); - l = list_lru_lock_irqsave(&deferred_split_lru, nid, folio_memcg(folio), &flags); + l = folio_list_lru_lock_irqsave(folio, &deferred_split_lru, &flags); if (__list_lru_del(&deferred_split_lru, l, &folio->_deferred_list, nid)) { if (folio_test_partially_mapped(folio)) { folio_clear_partially_mapped(folio); @@ -4286,7 +4279,7 @@ bool __folio_unqueue_deferred_split(struct folio *folio) } unqueued = true; } - list_lru_unlock_irqrestore(l, &flags); + folio_list_lru_unlock_irqrestore(folio, l, &flags); rcu_read_unlock(); return unqueued; /* useful for debug warnings */ @@ -4297,7 +4290,6 @@ void deferred_split_folio(struct folio *folio, bool partially_mapped) { struct list_lru_one *l; int nid; - struct mem_cgroup *memcg; unsigned long flags; /* @@ -4322,9 +4314,7 @@ void deferred_split_folio(struct folio *folio, bool partially_mapped) nid = folio_nid(folio); - rcu_read_lock(); - memcg = folio_memcg(folio); - l = list_lru_lock_irqsave(&deferred_split_lru, nid, memcg, &flags); + l = folio_list_lru_lock_irqsave(folio, &deferred_split_lru, &flags); if (partially_mapped) { if (!folio_test_partially_mapped(folio)) { folio_set_partially_mapped(folio); @@ -4337,9 +4327,9 @@ void deferred_split_folio(struct folio *folio, bool partially_mapped) /* partially mapped folios cannot become non-partially mapped */ VM_WARN_ON_FOLIO(folio_test_partially_mapped(folio), folio); } - __list_lru_add(&deferred_split_lru, l, &folio->_deferred_list, nid, memcg); - list_lru_unlock_irqrestore(l, &flags); - rcu_read_unlock(); + __list_lru_add(&deferred_split_lru, l, &folio->_deferred_list, nid, + folio_memcg(folio)); + folio_list_lru_unlock_irqrestore(folio, l, &flags); } static unsigned long deferred_split_count(struct shrinker *shrink, @@ -4445,16 +4435,13 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, * don't add it back to split_queue. */ if (!did_split && folio_test_partially_mapped(folio)) { - rcu_read_lock(); - l = list_lru_lock_irqsave(&deferred_split_lru, - folio_nid(folio), - folio_memcg(folio), - &flags); + l = folio_list_lru_lock_irqsave(folio, + &deferred_split_lru, + &flags); __list_lru_add(&deferred_split_lru, l, &folio->_deferred_list, folio_nid(folio), folio_memcg(folio)); - list_lru_unlock_irqrestore(l, &flags); - rcu_read_unlock(); + folio_list_lru_unlock_irqrestore(folio, l, &flags); } folio_put(folio); } diff --git a/mm/list_lru.c b/mm/list_lru.c index 1ccdd45b1d14..8d50741ef18d 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -173,6 +173,35 @@ void list_lru_unlock_irqrestore(struct list_lru_one *l, unsigned long *flags) unlock_list_lru(l, /*irq_off=*/true, /*irq_flags=*/flags); } +struct list_lru_one *folio_list_lru_lock(struct folio *folio, struct list_lru *lru) +{ + rcu_read_lock(); + return list_lru_lock(lru, folio_nid(folio), folio_memcg(folio)); +} + +void folio_list_lru_unlock(struct folio *folio, struct list_lru_one *l) +{ + list_lru_unlock(l); + rcu_read_unlock(); +} + +struct list_lru_one *folio_list_lru_lock_irqsave(struct folio *folio, + struct list_lru *lru, + unsigned long *flags) +{ + rcu_read_lock(); + return list_lru_lock_irqsave(lru, folio_nid(folio), + folio_memcg(folio), flags); +} + +void folio_list_lru_unlock_irqrestore(struct folio *folio, + struct list_lru_one *l, + unsigned long *flags) +{ + list_lru_unlock_irqrestore(l, flags); + rcu_read_unlock(); +} + bool __list_lru_add(struct list_lru *lru, struct list_lru_one *l, struct list_head *item, int nid, struct mem_cgroup *memcg)