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charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 28, 2021 at 8:53 AM Vlastimil Babka wrote: > > On 1/28/21 12:33 AM, 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 | 18 ++++++++---------- > > 1 file changed, 8 insertions(+), 10 deletions(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index d3f3701dfcd2..847369c19775 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) { > > @@ -266,12 +265,13 @@ 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); > > What's wrong with using DIV_ROUND_UP() here? I don't think there is anything wrong with DIV_ROUND_UP. Should be just different taste and result in shorter statement. > > > if (size <= old_size) > > - return 0; > > + goto out; > > Can this even happen? Seems to me it can't, so just remove this? Yes, it can. The maps use unsigned long value for bitmap, so any shrinker ID < 31 would fall into the same unsigned long, so we may see size <= old_size, but we need increase shrinker_nr_max since expand_shrinker_maps() is called iff id >= shrinker_nr_max. > > > > > if (!root_mem_cgroup) > > goto out; > > @@ -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; > > > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B214C433E0 for ; Thu, 28 Jan 2021 21:22:39 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BCB1464DE9 for ; Thu, 28 Jan 2021 21:22:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BCB1464DE9 Authentication-Results: mail.kernel.org; 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s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=iky+DugOhX1hDNU3AWl/82OLUGd7e4uUQOiW57Oek80=; b=QZZatvKHsIY2zUwzR/rzy/QDNDtd49EKVUfHm4+vLXkDqrl38p9KLCyDxA9EOcwJIM GNoLoBcMfSzaKAXsmIdeaX1JsWo8QTdLbIdnbAYuBj+ZmMTRA0F1juzPDpXLzdNiuXzz krF5OHsT8egllAh0tjK8SnZI66GmXrGHjFZ7XYTBWQlloi4Ed0AgkrrL8xNSzAbvXVVW JBjzvKCY5SMo3IVCjdg9aV+htlb6fU7q1hUwqmZPefzSzp6sriD3YGI2wDJAL3rPjuA4 f6nmkDSUSCkwUP+RdGNL2MDePyVXtZWAmubuTjI9RjGMX1yo+5OOInrzhF/6o2RTvdfi e//w== X-Gm-Message-State: AOAM53124f5DDHW2AVm9QaVOKM5fK95nqrtV6r6neTRNwd6u40nMxRtD 5maVXrjxMFK6ZymCwFR07beb4AgT+JbRcauoFcw= X-Google-Smtp-Source: ABdhPJwbu0bZDCE0LMnecgpA/vbNy1VOG2Gthhi97YaSV3LvX82i39z8aXTCyggUdueGOuBBwISGHCnSt9U8RpOtrVY= X-Received: by 2002:a05:6402:312e:: with SMTP id dd14mr1801362edb.366.1611868955853; Thu, 28 Jan 2021 13:22:35 -0800 (PST) MIME-Version: 1.0 References: <20210127233345.339910-1-shy828301@gmail.com> <20210127233345.339910-5-shy828301@gmail.com> <255b9236-3e0b-f6f6-4a72-5e69351a979a@suse.cz> In-Reply-To: <255b9236-3e0b-f6f6-4a72-5e69351a979a@suse.cz> From: Yang Shi Date: Thu, 28 Jan 2021 13:22:23 -0800 Message-ID: Subject: Re: [v5 PATCH 04/11] mm: vmscan: remove memcg_shrinker_map_size To: Vlastimil Babka Cc: Roman Gushchin , Kirill Tkhai , Shakeel Butt , Dave Chinner , Johannes Weiner , Michal Hocko , Andrew Morton , Linux MM , Linux FS-devel Mailing List , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" 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 Thu, Jan 28, 2021 at 8:53 AM Vlastimil Babka wrote: > > On 1/28/21 12:33 AM, 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 | 18 ++++++++---------- > > 1 file changed, 8 insertions(+), 10 deletions(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index d3f3701dfcd2..847369c19775 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) { > > @@ -266,12 +265,13 @@ 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); > > What's wrong with using DIV_ROUND_UP() here? I don't think there is anything wrong with DIV_ROUND_UP. Should be just different taste and result in shorter statement. > > > if (size <= old_size) > > - return 0; > > + goto out; > > Can this even happen? Seems to me it can't, so just remove this? Yes, it can. The maps use unsigned long value for bitmap, so any shrinker ID < 31 would fall into the same unsigned long, so we may see size <= old_size, but we need increase shrinker_nr_max since expand_shrinker_maps() is called iff id >= shrinker_nr_max. > > > > > if (!root_mem_cgroup) > > goto out; > > @@ -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; > > >