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Mon, 25 Jan 2021 08:36:16 +0000 (UTC) Received: from [192.168.15.14] by relay.sw.ru with esmtp (Exim 4.94) (envelope-from ) id 1l3xLj-000T1I-8x; Mon, 25 Jan 2021 11:35:51 +0300 Subject: Re: [v4 PATCH 04/11] mm: vmscan: remove memcg_shrinker_map_size To: Yang Shi , guro@fb.com, shakeelb@google.com, david@fromorbit.com, hannes@cmpxchg.org, mhocko@suse.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210121230621.654304-1-shy828301@gmail.com> <20210121230621.654304-5-shy828301@gmail.com> From: Kirill Tkhai Message-ID: Date: Mon, 25 Jan 2021 11:35:58 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <20210121230621.654304-5-shy828301@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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: On 22.01.2021 02:06, Yang Shi wrote: > Both memcg_shrinker_map_size and shrinker_nr_max is maintained, but actually the > map size can be calculated via shrinker_nr_max, so it seems unnecessary to keep both. > Remove memcg_shrinker_map_size since shrinker_nr_max is also used by iterating the > bit map. > > Signed-off-by: Yang Shi > --- > mm/vmscan.c | 16 +++++++--------- > 1 file changed, 7 insertions(+), 9 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index d3f3701dfcd2..40e7751ef961 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -185,8 +185,7 @@ static LIST_HEAD(shrinker_list); > static DECLARE_RWSEM(shrinker_rwsem); > > #ifdef CONFIG_MEMCG > - > -static int memcg_shrinker_map_size; > +static int shrinker_nr_max; > > static void free_shrinker_map_rcu(struct rcu_head *head) > { > @@ -248,7 +247,7 @@ int alloc_shrinker_maps(struct mem_cgroup *memcg) > return 0; > > down_write(&shrinker_rwsem); > - size = memcg_shrinker_map_size; > + size = (shrinker_nr_max / BITS_PER_LONG + 1) * sizeof(unsigned long); > for_each_node(nid) { > map = kvzalloc_node(sizeof(*map) + size, GFP_KERNEL, nid); > if (!map) { > @@ -266,10 +265,11 @@ int alloc_shrinker_maps(struct mem_cgroup *memcg) > static int expand_shrinker_maps(int new_id) > { > int size, old_size, ret = 0; > + int new_nr_max = new_id + 1; > struct mem_cgroup *memcg; > > - size = DIV_ROUND_UP(new_id + 1, BITS_PER_LONG) * sizeof(unsigned long); > - old_size = memcg_shrinker_map_size; > + size = (new_nr_max / BITS_PER_LONG + 1) * sizeof(unsigned long); > + old_size = (shrinker_nr_max / BITS_PER_LONG + 1) * sizeof(unsigned long); > > if (size <= old_size) > return 0; This looks a BUG: expand_shrinker_maps(id == 1) { old_size = 64; size = 64; ===>return 0 and shrinker_nr_max remains 0. } Then shrink_slab_memcg() misses this shrinker since shrinker_nr_max == 0. > > @@ -286,9 +286,10 @@ static int expand_shrinker_maps(int new_id) > goto out; > } > } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); > + > out: > if (!ret) > - memcg_shrinker_map_size = size; > + shrinker_nr_max = new_nr_max; > > return ret; > } > @@ -321,7 +322,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) > #define SHRINKER_REGISTERING ((struct shrinker *)~0UL) > > static DEFINE_IDR(shrinker_idr); > -static int shrinker_nr_max; > > static int prealloc_memcg_shrinker(struct shrinker *shrinker) > { > @@ -338,8 +338,6 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker) > idr_remove(&shrinker_idr, id); > goto unlock; > } > - > - shrinker_nr_max = id + 1; > } > shrinker->id = id; > ret = 0; >