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Subject: Re: [v7 PATCH 05/12] mm: memcontrol: rename shrinker_map to
 shrinker_info
To:     Yang Shi <shy828301@gmail.com>, Roman Gushchin <guro@fb.com>
Cc:     Vlastimil Babka <vbabka@suse.cz>,
        Shakeel Butt <shakeelb@google.com>,
        Dave Chinner <david@fromorbit.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@suse.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux MM <linux-mm@kvack.org>,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <20210209174646.1310591-1-shy828301@gmail.com>
 <20210209174646.1310591-6-shy828301@gmail.com>
 <20210209205014.GH524633@carbon.DHCP.thefacebook.com>
 <CAHbLzkr+5t5wTVRDih53ty-TcsMrmKxZ5iiPw1dwnDsz_URz=Q@mail.gmail.com>
From:   Kirill Tkhai <ktkhai@virtuozzo.com>
Message-ID: <5703130a-ea5b-3257-2ba0-3c25df010296@virtuozzo.com>
Date:   Thu, 11 Feb 2021 19:47:00 +0300
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On 10.02.2021 02:33, Yang Shi wrote:
> On Tue, Feb 9, 2021 at 12:50 PM Roman Gushchin <guro@fb.com> wrote:
>>
>> On Tue, Feb 09, 2021 at 09:46:39AM -0800, Yang Shi wrote:
>>> The following patch is going to add nr_deferred into shrinker_map, the change will
>>> make shrinker_map not only include map anymore, so rename it to "memcg_shrinker_info".
>>> And this should make the patch adding nr_deferred cleaner and readable and make
>>> review easier.  Also remove the "memcg_" prefix.
>>>
>>> Acked-by: Vlastimil Babka <vbabka@suse.cz>
>>> Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>
>>> Signed-off-by: Yang Shi <shy828301@gmail.com>
>>> ---
>>>  include/linux/memcontrol.h |  8 ++---
>>>  mm/memcontrol.c            |  6 ++--
>>>  mm/vmscan.c                | 62 +++++++++++++++++++-------------------
>>>  3 files changed, 38 insertions(+), 38 deletions(-)
>>>
>>> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
>>> index 1739f17e0939..4c9253896e25 100644
>>> --- a/include/linux/memcontrol.h
>>> +++ b/include/linux/memcontrol.h
>>> @@ -96,7 +96,7 @@ struct lruvec_stat {
>>>   * Bitmap of shrinker::id corresponding to memcg-aware shrinkers,
>>>   * which have elements charged to this memcg.
>>>   */
>>> -struct memcg_shrinker_map {
>>> +struct shrinker_info {
>>>       struct rcu_head rcu;
>>>       unsigned long map[];
>>>  };
>>> @@ -118,7 +118,7 @@ struct mem_cgroup_per_node {
>>>
>>>       struct mem_cgroup_reclaim_iter  iter;
>>>
>>> -     struct memcg_shrinker_map __rcu *shrinker_map;
>>> +     struct shrinker_info __rcu      *shrinker_info;
>>
>> Nice!
>>
>> I really like how it looks now in comparison to the v1. Thank you for
>> working on it!
> 
> Thanks a lot for all the great comments from all of you.
> 
>>
>>>
>>>       struct rb_node          tree_node;      /* RB tree node */
>>>       unsigned long           usage_in_excess;/* Set to the value by which */
>>> @@ -1581,8 +1581,8 @@ static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
>>>       return false;
>>>  }
>>>
>>> -int alloc_shrinker_maps(struct mem_cgroup *memcg);
>>> -void free_shrinker_maps(struct mem_cgroup *memcg);
>>> +int alloc_shrinker_info(struct mem_cgroup *memcg);
>>> +void free_shrinker_info(struct mem_cgroup *memcg);
>>>  void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id);
>>>  #else
>>>  #define mem_cgroup_sockets_enabled 0
>>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>>> index f5c9a0d2160b..f64ad0d044d9 100644
>>> --- a/mm/memcontrol.c
>>> +++ b/mm/memcontrol.c
>>> @@ -5246,11 +5246,11 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
>>>       struct mem_cgroup *memcg = mem_cgroup_from_css(css);
>>>
>>>       /*
>>> -      * A memcg must be visible for expand_shrinker_maps()
>>> +      * A memcg must be visible for expand_shrinker_info()
>>>        * by the time the maps are allocated. So, we allocate maps
>>>        * here, when for_each_mem_cgroup() can't skip it.
>>>        */
>>> -     if (alloc_shrinker_maps(memcg)) {
>>> +     if (alloc_shrinker_info(memcg)) {
>>>               mem_cgroup_id_remove(memcg);
>>>               return -ENOMEM;
>>>       }
>>> @@ -5314,7 +5314,7 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
>>>       vmpressure_cleanup(&memcg->vmpressure);
>>>       cancel_work_sync(&memcg->high_work);
>>>       mem_cgroup_remove_from_trees(memcg);
>>> -     free_shrinker_maps(memcg);
>>> +     free_shrinker_info(memcg);
>>>       memcg_free_kmem(memcg);
>>>       mem_cgroup_free(memcg);
>>>  }
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index 641077b09e5d..9436f9246d32 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -190,20 +190,20 @@ static int shrinker_nr_max;
>>>  #define NR_MAX_TO_SHR_MAP_SIZE(nr_max) \
>>>       (DIV_ROUND_UP(nr_max, BITS_PER_LONG) * sizeof(unsigned long))
>>>
>>> -static void free_shrinker_map_rcu(struct rcu_head *head)
>>> +static void free_shrinker_info_rcu(struct rcu_head *head)
>>>  {
>>> -     kvfree(container_of(head, struct memcg_shrinker_map, rcu));
>>> +     kvfree(container_of(head, struct shrinker_info, rcu));
>>>  }
>>>
>>> -static int expand_one_shrinker_map(struct mem_cgroup *memcg,
>>> +static int expand_one_shrinker_info(struct mem_cgroup *memcg,
>>>                                  int size, int old_size)
>>>  {
>>> -     struct memcg_shrinker_map *new, *old;
>>> +     struct shrinker_info *new, *old;
>>>       int nid;
>>>
>>>       for_each_node(nid) {
>>>               old = rcu_dereference_protected(
>>> -                     mem_cgroup_nodeinfo(memcg, nid)->shrinker_map, true);
>>> +                     mem_cgroup_nodeinfo(memcg, nid)->shrinker_info, true);
>>>               /* Not yet online memcg */
>>>               if (!old)
>>>                       return 0;
>>> @@ -216,17 +216,17 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg,
>>>               memset(new->map, (int)0xff, old_size);
>>>               memset((void *)new->map + old_size, 0, size - old_size);
>>>
>>> -             rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
>>> -             call_rcu(&old->rcu, free_shrinker_map_rcu);
>>> +             rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, new);
>>> +             call_rcu(&old->rcu, free_shrinker_info_rcu);
>>
>> Why not use kvfree_rcu() and get rid of free_shrinker_info_rcu() callback?
> 
> Just because this patch is aimed to rename the structure. I think it
> may be more preferred to have the cleanup in a separate patch?

I'd voted for a separate patch