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Sun, 26 Feb 2023 06:48:33 -0800 (PST) From: Qi Zheng To: akpm@linux-foundation.org, tkhai@ya.ru, hannes@cmpxchg.org, shakeelb@google.com, mhocko@kernel.org, roman.gushchin@linux.dev, muchun.song@linux.dev, david@redhat.com, shy828301@gmail.com Cc: sultan@kerneltoast.com, dave@stgolabs.net, penguin-kernel@I-love.SAKURA.ne.jp, paulmck@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qi Zheng Subject: [PATCH v3 4/8] mm: vmscan: add shrinker_srcu_generation Date: Sun, 26 Feb 2023 22:46:51 +0800 Message-Id: <20230226144655.79778-5-zhengqi.arch@bytedance.com> X-Mailer: git-send-email 2.24.3 (Apple Git-128) In-Reply-To: <20230226144655.79778-1-zhengqi.arch@bytedance.com> References: <20230226144655.79778-1-zhengqi.arch@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: AA35C18000B X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: a899m5ou9dwm5ucs6ykrpanz1zosejhw X-HE-Tag: 1677422914-261083 X-HE-Meta: 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 gk5Gq78k 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Kirill Tkhai After we make slab shrink lockless with SRCU, the longest sleep unregister_shrinker() will be a sleep waiting for all do_shrink_slab() calls. To aviod long unbreakable action in the unregister_shrinker(), add shrinker_srcu_generation to restore a check similar to the rwsem_is_contendent() check that we had before. And for memcg slab shrink, we unlock SRCU and continue iterations from the next shrinker id. Signed-off-by: Kirill Tkhai Signed-off-by: Qi Zheng --- mm/vmscan.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 490764f8e085..99e852c0ab9e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -204,6 +204,7 @@ static void set_task_reclaim_state(struct task_struct *task, LIST_HEAD(shrinker_list); DECLARE_RWSEM(shrinker_rwsem); DEFINE_SRCU(shrinker_srcu); +static atomic_t shrinker_srcu_generation = ATOMIC_INIT(0); #ifdef CONFIG_MEMCG static int shrinker_nr_max; @@ -782,6 +783,7 @@ void unregister_shrinker(struct shrinker *shrinker) debugfs_entry = shrinker_debugfs_remove(shrinker); up_write(&shrinker_rwsem); + atomic_inc(&shrinker_srcu_generation); synchronize_srcu(&shrinker_srcu); debugfs_remove_recursive(debugfs_entry); @@ -803,6 +805,7 @@ void synchronize_shrinkers(void) { down_write(&shrinker_rwsem); up_write(&shrinker_rwsem); + atomic_inc(&shrinker_srcu_generation); synchronize_srcu(&shrinker_srcu); } EXPORT_SYMBOL(synchronize_shrinkers); @@ -912,18 +915,20 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, { struct shrinker_info *info; unsigned long ret, freed = 0; - int srcu_idx; - int i; + int srcu_idx, generation; + int i = 0; if (!mem_cgroup_online(memcg)) return 0; +again: srcu_idx = srcu_read_lock(&shrinker_srcu); info = shrinker_info_srcu(memcg, nid); if (unlikely(!info)) goto unlock; - for_each_set_bit(i, info->map, info->map_nr_max) { + generation = atomic_read(&shrinker_srcu_generation); + for_each_set_bit_from(i, info->map, info->map_nr_max) { struct shrink_control sc = { .gfp_mask = gfp_mask, .nid = nid, @@ -969,6 +974,11 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, set_shrinker_bit(memcg, nid, i); } freed += ret; + if (atomic_read(&shrinker_srcu_generation) != generation) { + srcu_read_unlock(&shrinker_srcu, srcu_idx); + i++; + goto again; + } } unlock: srcu_read_unlock(&shrinker_srcu, srcu_idx); @@ -1008,7 +1018,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, { unsigned long ret, freed = 0; struct shrinker *shrinker; - int srcu_idx; + int srcu_idx, generation; /* * The root memcg might be allocated even though memcg is disabled @@ -1022,6 +1032,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, srcu_idx = srcu_read_lock(&shrinker_srcu); + generation = atomic_read(&shrinker_srcu_generation); list_for_each_entry_srcu(shrinker, &shrinker_list, list, srcu_read_lock_held(&shrinker_srcu)) { struct shrink_control sc = { @@ -1034,6 +1045,11 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, if (ret == SHRINK_EMPTY) ret = 0; freed += ret; + + if (atomic_read(&shrinker_srcu_generation) != generation) { + freed = freed ? : 1; + break; + } } srcu_read_unlock(&shrinker_srcu, srcu_idx); -- 2.20.1